01.15.2015 - by Tom Saxton
Workplace Charging – The Goldilocks Approach

Workplace Charging – The Goldilocks Approach

Charger installation. John Kalb

Charger installation. John Kalb

Many companies are considering providing workplace charging for their employees and finding they are in new territory with many options to consider. We at Plug In America would like to share what we have learned having been involved for over 10 years in both using charging infrastructure as drivers and advising site hosts of all types in how to provide effective charging facilities.


There are many reasons a company may be considering providing workplace charging. It could be to attract and retain forward-thinking employees, to enhance a company’s “green” image, to gain points toward LEED certification, or to raise awareness of electric vehicles.

Our analysis and recommendations are based on the goal of using workplace charging to increase the adoption of electric vehicles, which ties in with many of the reasons we find companies are considering making charging available in the workplace. Even when this is not an explicit goal at a given company, understanding the issues presented here may be helpful in evaluating charging options.

We also want to minimize the cost to the employer while meeting the goal of encouraging increased use of electric vehicles. These considerations include infrastructure costs, operating costs, maintenance costs, and efficient use of employee time.

There is certainly no one-size-fits-all approach that meets the goals and needs of every company. The ideas presented here are meant to serve as a starting point, a baseline plan that can be used to inform the analysis of corporate goals, infrastructure considerations, and employee interests.


Level 1 refers to charging at 120V. This can be from an ordinary outlet using a portable charging device or from a dedicated Level 1 station that has the proper electronics and plug to connect directly to a plug-in electric vehicle. For long term loads, like charging a vehicle, the current drawn is generally limited to 12A, which yields 1.44 kilowatts (kW) of charging.

Level 2 refers to charging at higher voltage, 208V to 240V. The current limit for Level 2 stations is typically 30 to 32 amps (~7 kW), but can be anything from 15A to 80A (up to 19.2 kW). In principle, Level 2 charging can be accomplished with a 240V outlet (NEMA 14-50, for example), but we strongly prefer charging stations for Level 2 to avoid a number of safety, liability, and usability issues.

DC Quick Charge This charging method bypasses the vehicle’s on-board AC charging equipment and sends high voltage (300V to 400V) DC directly to the battery, at rates between 20 and 130 kW. These are expensive to install and operate, and are typically used for road trips or other situations where extra charge is needed in a hurry, not for a workday charging session.

The “Just Right” Fee

Problem: Free Reduces Availability
Free charging sounds like the best incentive to get people to consider electric vehicles, but the cost of electricity is not a barrier to EV adoption. An exact comparison with gas depends on a number of factors, but think of driving on electricity as equivalent to getting gas for less than $1 per gallon. Free charging makes the cost benefit more apparent, but has a couple of problems. First, it sets an expectation that charging will always be free, something that generally isn’t sustainable. A short-term pilot with free charging can be very effective in kickstarting awareness of electric vehicles, and some companies may want to continue to provide free charging even as EVs rise in popularity.

However, if free charging drives demand to a level that can’t be met, the resulting oversubscription can create problems that reduce EV adoption. Free charging motivates everyone to charge at work because it’s cheaper than charging at home. Charging that is oversubscribed is undependable and therefore people who can’t charge at home won’t find it a viable option. The only people who can use free charging are those who don’t need it because they have a more reliable alternative. This creates conflict between drivers who need charging to get home and others who just want to charge because it’s free. This built-in conflict can even create a hostile environment at work. Who wants to get into a shouting match over fueling their car so they can get home?

When free charging leads to oversubscription and reduces charging availability for those who need to charge, it discourages EV adoption among those who could most benefit from charging at work.

Problem: Overly Cheap Charging Shifts Off-Peak Use to On-Peak
Like free charging, billing at a rate that’s below the market price for electricity incentivizes shifting charging from overnight at home to charging at work during the day. As EV adoption increases, this puts extra strain on the grid and increases energy costs.
Problem: Overly Expensive Charging Can Hurt Adoption Or Usage

Paid charging billed far above the cost of electricity erases the economic advantage of driving electric. People who can’t charge at home thus can’t use this as a way to make driving electric financially viable. This therefore will not increase EV adoption. Likewise it can’t substantially increase use of EVs if it makes driving electric cost more than burning gas.

Solution: Charge a Little Over Market Price
The solution is to provide charging billed at just a little above local home rates. This extends the economic advantages of driving electric to those who cannot charge at home. It also eliminates the incentive to shift charging from home to work, reducing the number of stations needed to satisfy demand. Together these benefits minimize the infrastructure cost of providing charging at work and focus the benefits on those who need it the most.

Note that billing for public charging is different; other issues are at play there.

What Technology To Choose?

Problem: Level 2 Infrastructure Requires Resource Management
A typical Level 2 charging station delivers enough power to add approximately 200 miles of electric driving range in a workday, far more than the average commuter needs to charge up. Thus, there’s pressure to take time out of the day to go out and shuffle cars so the next car can charge. Employees at workplaces with oversubscribed Level 2 chargers have developed dedicated mailing lists and sophisticated notification systems to coordinate swapping vehicles at charging stations.

In the long run, employee distraction is probably the most expensive cost in providing Level 2 workplace charging, easily exceeding the cost of electricity and, over time, exceeding the cost of equipment and installation.

Problem: Simultaneous Level 2 Charging Risks Utility Demand Charges
If there’s enough Level 2 charging that shuffling cars during the day isn’t needed, then the vast majority of EVs will get their full charge in the first couple of hours in the morning. Because of this, compared to a more gradual charging method, a company’s exposure to utility demand charges is tripled or worse, another hidden cost that can exceed the more obvious electricity, equipment and install costs.

Problem: Level 2 Billing Schemes Create Problems
There are three basic ways to bill for charging, and none of them work well enough to be the predominant billing method in the workplace.

Billing by energy delivered, kWh, is the closest model to selling gasoline by the gallon, but when demand for charging is high and turnover is required to get everyone charged, then the scarce resource isn’t the electricity, it is the opportunity to charge. Billing by energy use doesn’t incentivize people to unplug when their vehicle is done charging.

Billing by hour is the obvious solution for getting people to free up the charging station when they are done charging, but is unfair because some vehicles draw energy at twice the rate, or more, of others.

Billing by session, like $5 per charge, combines the worst attributes of the above for Level 2 charging: it offers no incentive to move after charging is complete and is even more unfair than billing by time.

Problem: Networked Billing Stations Raise Costs
Stations with built-in billing and network connectivity provide a number of valuable benefits. In addition to enabling billing, they can also control access, collect data on use, and allow remote monitoring for maintenance issues. Many site hosts choose to install these sophisticated stations for these other benefits even when they provide free charging.

However, these stations add costs both for the equipment purchase and operating expenses, which can be problematic when used to provide daily charging for drivers who can’t charge at home.

The incremental cost for charging units with billing can equate to the cost of electricity for years worth of charging. Passing that cost on to users of the stations puts up a barrier to EV adoption for those who can’t install a simple charging station at home.

Because electricity is so inexpensive, billing overhead alone can double the cost of providing charging. Again, passing this cost on to users discourages those who can’t charge at home from driving electric.

Solution: Fixed-Rate Parking Pass And Simple Charging Stations

With Level 1 charging, billing can be handled by having employees pay for a parking pass at a fixed monthly rate that allows them to use the charging. Charging for 8 hours will yield about 35 miles of range, which is enough for most commutes. So the billing rate could be set to be just a little above the cost for 8 hours of Level 1 charging, or about 11.5 kWh. If someone needs only six hours, they are overpaying by 33%, which is still far better than paying double at a billed Level 2 station. Because charging takes most of the day, there’s no need to run out and shuffle cars around, and exposure to demand charges is also lowered.1

EV drivers can do the legwork needed for enforcement by reporting violators to facilities. Facilities can then issue a warning or call a tow truck.

Simple Outlets
Simple outlets (NEMA 5-15 or NEMA 5-20) are very inexpensive and may already be available in employee parking lots. If already available, providing charging can be as simple as adopting policy for giving permission to employees to use the existing outlets. These outlets need to be on dedicated circuits, which need to be rated for at least 15 amps and preferably for 20 amps. They should be situated such that charging cords won’t cause a tripping or ADA hazard.

Dedicated Level 1 Stations
Level 1 charging stations have a number of advantages. Charging stations use J1772 connectors which are designed for thousands of plug/unplug cycles, are weather-resistant, have built-in ground fault protection, and communicate the maximum safe charging level to the car. In addition, a dedicated charging station is preferable to connecting the car to a simple outlet with a charging cord; the cord takes time to retrieve and put away, and is a potential theft target. Ideally charging is fast and convenient: 10 seconds to plug in and you’re done.

Although Level 1 charging stations are more expensive than outlets, the cost of the stations may not add much to the total cost of installing charging infrastructure when new wiring is required.

Level 2 For Increased Availability
Level 1 may not be sufficient to meet everyone’s charging needs, so some Level 2 should also be available, but at a higher billing rate than Level 1. Low power Level 2 stations (12 to 15 amps) can be administered in the same way as Level 1 stations, using inexpensive stations and controlling access via parking passes sold at a slight premium to an assumed 8 hours of charging per day at the local daytime utility rate. Higher power Level 2 stations (30 amps or more) can be provided for those who occasionally need charging, and can be billed at higher rates to cover the costs of more sophisticated stations needed for time-based billing.

DC Quick Charging For Edge Cases
DC Quick Charging can also make sense as a safety net for those odd cases where someone needs to charge quickly. This could be on site at the workplace for large companies or just conveniently located nearby.


Generally speaking, workplace charging should consist of mostly Level 1 charging, billed at just above the cost of 8 hours of charging per day, with some Level 2 available at a higher billing rate. Even though Level 1 charging stations and installation may not be any less expensive than non-billing Level 2 stations, this will meet the goal of increasing EV adoption and use while minimizing infrastructure costs, utility demand charges, and lost employee time.

1In some cases, peak utility rates may tip the balance toward Level 2 charging which finishes early in the work day. Providing lots of paid Level 2 is fine if it really makes more sense than Level 1.

Updated February 20, 2015.

44 comments on “Workplace Charging – The Goldilocks Approach”
  1. Savannah says:

    I liked the idea of a monthly parking pass fee as the company I work at is currently worried about the administrative time needed to calculate how much is owed by each person if we adopted simple outlets for L1 charging. I was curious what you would do if we didn’t have enough spots for every person that wanted to use the station. Would you limit the number of parking passes sold based on how many outlets are available? And then employees could split the cost with another employee if they wanted to share the space (park every other day)? Or is there another way to do this that has worked for you or someone you know. Thanks

  2. Tyler H. says:

    I just encountered this. We have free charging at work, and most of the users each day are people who don’t need to charge there. It’s entirely opportunistic “give me free electricity.”

    I can’t believe how shortsighted it is to put in free charging. There’s no incentive to manage it well (it costs money) for people to take care of it (it isn’t mine) to move their cars (who cares), or to add capacity (we already have ports).

    The article is exactly right, it attracts people who already have an EV and a place to charge, as this is just a “convenience” .

    For serious EV adoption, access to a charger cannot be a convenience. Workplace charging must become the primary place to charge for people in apartments who don’t own their own homes and can’t install the infrastructure.

    People don’t buy EVs when they have no place to plug them in reliably. The average person spends 8 hours at work, this is a hand in glove solution.

  3. Kent says:

    I cannot believe what I am reading. You are saying a person would buy an electric car even though they had no way of charging it at home….. and you believe that person should be given the priority at work for charging their car over a person who can charge their car at home. I would fire that person because I don’t want anyone who would make a poor decision like that, working at my company. your creditability as an objective writer got flushed down the toilet on that one.

    1. Tom Saxton says:

      The idea is that employers make charging available and reliable so people can choose to drive electric even if they can’t charge at home.

  4. Matt says:

    Finally, an article that is reasonable when looking at EV infrastructure. I don’t own an EV and I think it’s unfair to those of us who can’t afford a low range vehicle to foot the bill for those who do. So much whining from the elite about “free” power on the backs of others. Pay for your own power, should be the norm. A business will NEVER be able to provide the power cheaper than someone charging at home. Add a method of payment to the charger, and you have a 3500.00 charger, prone to maintenance costs, monthly cell fees, upgrade costs, and security issues. Tally it all up and a business will pay over 2.00 an hour to provide “free” electric to the leeches who should be paying for their own”gas” just like everyone else.

    1. Tom Saxton says:

      Hi Matt,

      Thanks for the praise for the article.

      Have you looked at the total cost of ownership for an EV? Used EVs are quite affordable, especially when you consider the savings in fuel. People with long commutes can likely make their car payments with what they save in gas, making a used EV cheaper than a gas car that’s already paid for.

      In some circumstances, a business can provide cheaper power than available at home. Businesses rates are generally a little lower than residential. Even more, in areas where solar power is overproducing, charging during the day can be cheaper and better for the grid than charging overnight at home.

      I agree that networked charging stations add considerable costs to providing charging, but they aren’t the only choice. Businesses can provide free or paid charging with simple, less expensive, stations, making the long term overhead negligible even compared to the low cost of electricity.

      The whole point of workplace charging is to make EVs practical and affordable for more people, not just those wealthy enough to buy new vehicles. We all subsidize gas car drivers by allowing them pollute our air and alter our climate for free. Until we have a fair carbon tax that makes those costs visible to everyone, we need to support EVs as much as possible, and we need to do it in ways that are effective in accelerating the adoption and increasing the use of more efficient vehicles that can be powered by clean, renewable energy.

      1. Matt says:

        I agree. Unfortunately, I think you may have missed my point. Your views are NOT shared by the majority of the elites out there crying like Cookie Monsters for their “free” power. Stop the sniveling and follow your advice. Pay a flat monthly fee at your workplace and stop expecting coworkers or business owners to bear the costs for your “gas”. Too many smug folks hiding behind their “let’s save the planet” b.s. In order to get a free ride. If you really want to make a difference, ride a bicycle. The EV costs a ton to make in pollution AND battery technology, while better, still makes a HUGE impact on the environment.

        1. Tom Saxton says:

          I’m interested to hear how you determined that a majority of EV drivers are unwilling to pay for charging. I’ve had the opposite experience. In fact, I manage community support for a charging station that was going to go away when the host city decided to stop paying for the power. As soon as I asked the community of drivers who use that charger if they wanted to support it, I had 3 years of funding donated, and the charging station was saved.

          I think it’s likely that you’ve had a bad experience with a vocal minority of drivers who don’t understand the expenses involved in providing charging and don’t represent the majority who appreciate key charging infrastructure.

          Can you tell us more about your experience? Where is your charging located? By what forum are people complaining about having to pay for charging?

          Perhaps we should write a similar blog on how to set up sustainable, effective public charging. There are alternatives to expensive, networked charging stations.

  5. Rich F. says:

    Shouldn’t our government support this to set the example?

    We the people: your voice in our government–Please read on –>

    Workplace Charging Challenge: Install Stations at the 847,000 Government Locations & Allow Employee Use

    The Administrations Workplace Charging Challenge(WCC) is admirable! Results: 150 partners, 300 locations, 4000 stations. However, only (1) Federal Agency (DOT) is identified as a partner on WCC with 1 location listed. Why isn’t the government setting the example for WCC?

  6. Darren Schurig says:

    The entire premise of this article is short sighted. At present EVs are a miniscule fraction of the total number of vehicles on the road in California as we all know. At recently over 100,000 cars in California, even if all of us plugged in to Level 2 charging at noon during the week, it wouldn’t amount to even a tiny blip on the grid load.

    This isn’t the time to be nit picking points like this, we need to do whatever we can to convert commuters to electric driving with any means necessary. We are already throwing public money at it by the millions, affording special privileges like HOV access, special parking stalls and even free parking to name a few and broadcasting the message to anyone in anyway we can on our own time. Whatever it takes. NONE of it is sustainable. We all know that and we shouldn’t care right now.

    If being able to drive to work and charge for free is that final incentive that puts someone over the EV precipice, fantastic. A colleague of mine just purchased a Kia Soul EV the day after free charging stations were commissioned at work, that was the last piece of the puzzle for him – spectacular!

    All of this will go away in due time, we will fix it all later when it won’t derail the progress we are making now. Maybe two years, maybe ten, it doesn’t matter. It is all at such an infancy now, we don’t even need to have a plan yet.

    I personally worked on the teams that designed, engineered and built the PNGV prototypes in the mid 90’s that achieved up to 80 mpg real world for five passenger vehicles. Twenty years ago! Then I observed helplessly as it was all dismantled and scrapped. We have waited twenty years for such a resurgence in transportation fuel innovation, please let it get its legs under it before you weight it down with long term issues like sustainability.


    1. Tom says:

      Hi Darren,

      I think you’re saying we want companies to give free charging to everyone since it motivates people to consider EVs. That would be great. I totally support that.

      One of the big issues we’re trying to resolve with this blog is with companies that put in limited free charging which then gets oversubscribed. How will your friend if the free charging gets overwhelmed and he/she can no longer reliably charge at work? If it was just a nudge need to make the jump to PEV, no big deal. If it was an important part of making the budget for getting the car, that’s more of a problem. If workplace charging is critical, because charging at home is impossible, then it’s a total disaster.

      If companies have limited resources for providing workplace charging, we want to make sure they are making the choices that will best support a positive experience for EV drivers.

      Thanks for sharing your thoughts.


      1. Excellent article Tom. And long term, I think you are heading in the right direction. For now though, I think we are all in agreement that charging at work is a great incentive for employees.

        As you said, the demand – and fair usage – is a challenge. To this end, we have been working on an app that enables corporate users to schedule their charges. No more back and forth emails, no more stress. We would love to get your thoughts on our app. Please let me know if you can have a short chat with us.

        In the meantime, we would appreciate everyone filling out this survey for us. (bit.ly/evParkSurvey). Happy to share the reusul


  7. Bill Engelke says:

    After much prodding by me, the University of Alabama added a couple of Chargepoint stations (4 plugs) to its parking decks. I’m quite sure I am the very only user. At first, one of the stations was free, so I went over there. As soon as that was discovered, this one also was made for-fee. The fee is substantial (85 cents per hour, which is over 4 times what I pay to charge at home using Alabama Power – and $25.00 per hour after 4 hours, to ensure nobody uses it to park their electric car all day. There is a $50 fine for parking an ICE car in one of the 4 slots). Anyway, since it is so much more expensive than charging at home, I use these slots only as an emergency measure, i.e., unanticipated travel depleted my battery, and I need it to get home. So although one could theoretically do workplace charging, it would, as you say require them to move the car at lunch, and would also be expensive. A larger number of 120v outlets would be better – but I doubt this could be made available for free.

    1. Tom says:

      This is a great illustration of the difference between public and workplace charging.

      For public charging, a high billing rate ensures that stations are available for drivers who really need to charge rather than constantly in use by people who are only charging there because it’s cheap or free. I was recently in need of charging away from home.

      Workplace charging needs to be primarily billed at a price that isn’t too much above the cost of local home charging. If it’s too expensive, then it takes away the economic advantage of driving electric for people who need to charge at work. This means something other than a high billing rate needs to be done to ensure workplace charging is available to those who really need it, as explained in more detail in the blog.

      Recently, I found myself low on charge and was happy to pay four times what I pay to charge at home to be able to charge while I was at a show. I would not be happy to pay at that rate for daily charging at work.

  8. Stuart says:

    You got most of the way there with this article, but it still seems to emphasize parking in a company-owned lot. I live in Vancouver where the monthly parking charge can be upward of $500. This is for an ICE vehicle. The cost of electricity is not significant in relation to the monthly charge, but the cost of the hardware is. L2 charging hardware IS more expensive than L1. Reparking cars when charged is a non-starter (that requires more parking real estate) and penalizing EV drivers for leaving them parked seems equally backward.

    I’m enjoying the discussion. I can hardly wait for the acknowledgement of this problem and the implementation of the practical solution (ubiquitous L1 charging).

    1. Tom says:

      In general, public charging is a different situation than workplace charging, but monthly parking seems pretty similar to workplace charging. The same advice presented here works in that situation: install mostly Level 1 charging and require a specific parking permit to park in the spaces with access to charging so the charging is reserved and thus reliable.

      The cost of the equipment depends on how fancy you get. Clipper Creek sells Level 1 stations (the ACS-15 and ACS-20) for $495. Their low cost Level 2 unit (the LCS-20) is less expensive at $395.

      At the other end of the spectrum, Telefonix has a Level 1 station with a cord retraction system that sells for $1,495.

      There are many other products on the market, these are just examples to show that the cost of Level 1 vs. Level 2 stations isn’t significant when comparing units with comparable features.

      You can also do Level 1 or Level 2 charging with simple outlets, but that has the problems mentioned in the blog.

  9. Tom says:

    I’ve updated the blog and PDF to better describe the disadvantages of shifting charging from off-peak to on-peak. The issues are many and some are complex. The most obvious issue is in areas where time-of-use billing is used as a cost signal to mitigate the increased cost of production associated with power plants that that handle peak demand. Even absent those signals, increasing peak electric use increases the cost of production. Thus, it doesn’t make economic sense to give EV owners who can charge overnight at home an incentive to charge during the day at work.

    This is very different from enabling potential EV owners who can’t charge at home by providing a cost-effect charging opportunity at work.

    There’s also an environmental issue to consider. Generally speaking, charging off-peak uses base load generation while charging on-peak may increase use of peaking plants. Depending on the CO2 footprint of base vs. peaking plants, one may have a benefit over the other. Most peaking plants are burning natural gas. Today, base load generation may be more or less carbon intensive than natural gas. As we transition our grid to more environmentally responsible sources, the environmental case for charging off-peak will become stronger than it is today.

  10. Anonymous says:

    There are several things written here as fact that seem to be based on opinion. When making statements that you want people to trust, you should have supporting information. There are so many examples of opinion stated as fact that I won’t single them all out, but emissions related to charging is one of your first points made and is missing supporting information. Also, the above claim seems to ignore the well documented fact that L1 charging is less efficient than L2 charging (meaning less energy goes into the battery with L1 than L2 for each kWh from the grid). This reduced efficiency means more wasted electricity, which means more wasted money and more emissions due to charging.

    Another opinion stated as fact is that L1 stations reduce infrastructure cost. How so? You acknowledge that the stations and installation cost are the same…so where is the savings in the infrastructure?

    Finally, the proposed solutions seem to be pretty short sighted. If employees shuffling cars around is wasteful, aren’t employees policing each other, having facilities management involved with ticketing and towing, etc. also wasteful? At what point is administration and management of this (monthly billing, policing, etc.) actually more burden than the cost of the electricity alone? Electricity is fairly cheap, and company labor resources are not! What about the value to a company to broadcast their strong support of employees choosing plug in vehicles for their corporate sustainability initiatives? What about future-proofing EVSE infrastructure; when smart grids/cars/facilities are able to turn on the car’s charging remotely when it makes sense, will L1 still be beneficial? Just because it is plugged into a J1772 in the morning does NOT mean it needs to start charging at that very moment! If demand charges and emissions are a true concern, isn’t a L2 infrastructure with “smart” cars more sensible in the future? This would avoid lost employee time AND demand charge increases. Where does a solar canopy fit into this strategy?

    While there are many interesting ideas and some lessons learned from the past included in this article, it seems to create more questions than answers. A facilities manager coming here isn’t finding any solutions, or at least not obvious ones!

    1. Tom says:

      I think there are plenty of useful solutions proposed here which meet the goal of enabling broader EV adoption while minimizing employer costs, and many commenters here and elsewhere agree. There are other goals for providing EV charging, but that’s beyond the scope of our recommendations, although many will overlap well. I’m happy to discuss your questions. Send me your contact info via the “Contact Us” link at the bottom of this page.

      1. Anonymous says:

        What useful solutions have been proposed here which minimize employer costs? Again, you say, “Level 1 charging stations and installation may not be any less expensive than non-billing Level 2 stations” yourself! So, where are the cost savings? Demand charges? These are highly variable and can be avoided through more ways than just reduced charge rate (such as staged start time), but that seems to be what you are basing your opinion on. What else is saving cost, if not installation and equipment?

        Imagine it from the perspective of a facilities manager. If they follow your recommendation and install L1 EVSE, what costs would they save? When they are being asked to install L2 equipment (to increase utility for users), how can they justify having some L1 and some L2 units instead of only L2 units to keep it simple? What about installing an L2 unit which can be adjusted for charge rate preference through settings/software so that it can be updated in the future for higher or lower charge rates, if preferred?

        I’m asking these questions here to generate discussion related to your claims, since your opinions are stated here as fact. I think it’s important to be clear why you’re making these recommendations if facilities managers were to find this and base their decisions on your opinions. In many cases they’re making an investment that will last decades, so they should be thinking long term.

        1. Tom says:

          The cost savings we described here are the long term total costs of our proposed solution compared to simpler schemes that use only L2, either free or billed, while meeting the goal of increasing EV adoption. These costs are enumerated in the post, but I’ll repeat them:

          • reduced exposure to utility demand charges
          • reduced number of stations needed by reducing use by owners who can charge at home
          • reduced employee time spent managing use of charging stations
          • reduced cost of equipment when compared to using only stations with billing capability

          The solutions we propose that are not in common use and not widely promoted are:

          • L1 charging billed via special parking permits
          • use of low-power L2, also billed by parking permit
          • use of progressive billing rates to encourage use of low-power, low-cost charging

          The goal here is to give companies options for installing charging that will be both cost-effective and reliable for the drivers who need it as well as insight into how different policies will effect their impact in increasing EV adoption. Our recommendation is a baseline from which we expect stakeholders to adapt to their specific goals and constraints.

  11. DJ Christian says:

    Thanks for giving this a name, Tom.

  12. Brent says:

    I agree with most of the arguments in this article, but I think the author is confusing the value of low amperage charging (i.e. slow) with L1 vs L2 charging. L2 charging at 208/240V is actually much cheaper to wire and install than 120V (for the same amperage). If you are three-phase, like most large businesses are in the USA, there are big gains when you are wiring multiple circuits each at 208V. With 3 phase power, running 3 220V chargers takes 3 wires and running 3 110V chargers of the same amperage takes 4.

    There are now low amp L2 chargers (20A or less) commercially available which give all the benefits of L1 charging but for less installation cost when done in groups. Two I know about are PowerPost (available as L1 or L2) and TurboDock (L2).

    1. Tom says:

      Low-powerL2 can be a good option, has been available for a couple of years, and is mentioned in the discussion. The vast majority of commutes can be handled with 8 hours of L1 at work. Low-power L2 (e.g. 208V/15A, about 3 kW) will charge most vehicles twice as fast. That’s great for employees who need it, but if that’s not needed then you have the issues discussed: twice the exposure to utility demand charges or a need to swap cars at mid-day, either of which can be more expensive than running an additional wire. Companies should consider all of the options and also find out what their employees actually need.

      1. Brent says:

        PowerPost originally announced a L2 charger that would be half that, two sharing a 15A connection, but they did not end up commercializing it. Something like this is the way to go for slow charging. L1 charging at the same amperage is almost always going to be more expensive for workplace charging (because of the extra wiring and breakers). Pluginamerica could be encouraging EVSE manufacturers to provide more low amp workplace chargers to fill this void.

        1. Tom says:

          There are cost considerations other than the initial install cost that have to be considered. Those issues are what we are trying to expose here. In the long term, companies will want charging that fits the needs of the employees, minimizes lost work time, works with the local rate structure, allows appropriate access control, and enables cost-effective billing methodology. Even if it requires a higher initial install cost, it’s important to meet these other long-term needs.

  13. Dave R says:

    So, how do you bill for occasional use?

    There’s a big opportunity for someone to build a standalone, low cost energy accounting system. I think it could be done for $100/station…

    1. Tom says:

      The cheapest system I know about is Liberty Technologies. What they offer is really an access control system which can be interfaced with third-party billing systems, or parking lots kiosks, or hotel front desks. Their hardware is $600/unit, plus an annual subscription fee. If you can build a reliable, durable system for $100/unit, you’ll be well received in the marketplace.

  14. Paul Scott says:

    Great piece, Tom! L1, hopefully paired with a PV carport system, is clearly the way to go. I don’t mind if a company or school has the resources to install an L1 station, but simple robust 20 amp plugs work very well, too. It’s not a big deal to get your charge cable out and put it away. An old towel in the trunk keeps and your hands clean.

    As for paying, KISS is best. Keep it simple. A $15 or $30/month fee is very simple, but not completely fair. I like the idea of mapping everyone’s home address to school, doubling that, and charging the kWh rate for the mileage based on 4 miles/kWh. It’s much closer to exact usage, yet still doesn’t require a meter.

    1. Tom says:

      That’s another great option. Thanks, Paul!

  15. While many articles focus on workplace infrastructure –the types and costs – few articles cover details on vehicles driven, how far they’re driven and operating costs.

    What do we know about typical commute distances of employees and how many miles per day they drive? Are employees driving PHEVs, or BEVs … and what models, so we have an undstanding of usable range. Is workplace charging a necessity (live in shared community or appartment without dedicated parking), a benefit (a 30-40 mile electric range PHEV now allow round-trip e-commutes), or a luxury (own a 100+ mile BEV capable of making full commute without charging).


    Having some data is an useful starting point to understanding the need for what “type of charging equipment” is needed and “number of each type” of charging stall. Offering many charging stalls can be a costly infrastructure project, particularly if the wrong type, or number of charging stalls are deployed.


    As part of learning about the electric vehicles that employees own and how they typically commute a business can consider other commute strategies and incentives. eg: Offer incentive to employees purchasing an EV with longer range that usually does not depend on workplace charging. Offering discounted monthly membership to a local fast charging network may be more cost effective that installing and maintaining charging equipment until a larger number of employees drive electric. Offering information or partnerships with landlords to install residential charging (apartments and condos). Offer free charging to employees ridesharing, or car pooling.

    Beyond the needs of current employees, how will commuting change in the next 2-5 years? Are the state, or local incentives for employers to assist employees in their daily travel needs?

    What if driving plays a significant role as part of business operations? Does the business maintain any vehicles that woud benefit from lower operational cost of EVs? eg: a small fleet use for short trips of 10-50 miles. What about shuttle vehicles to move employees between facilities?

    A workplace charging solution, or strategy is much more than just adding some charging infrastructure to a parking lot.

    1. Tom says:

      I agree that companies should survey their employees to find their commute distances and interest in driving electric to guide the balance between dedicated L1, dedicated low power L2 (3.6 kW) and perhaps metered medium power L2 (7 kW).

      There are many things to consider in developing a plan for sustainable commuting, but we wanted to focus on growing the use of plug-in vehicles by enabling those who can’t charge at home with workplace charging for this piece.

  16. Anonymous says:

    I do not understand your point that “Problem – Overly Cheap Charging Can Hurt The Environment”. While electricity does cost more during the day a 20 KW of power needs to be generated to fill my car up one way or the other. I do not see how it impacts the environment any more if I pull that power during the day or at night. It will be more of a strain on the electric grid but I don’t see how that impacts the environment.

    In addition, charging more then the “low” rate for power would discourage me from purchasing an electric car. I am a 2 electric car family and need to be able to charge @ work since I already charge 1 car @ home. If work was going to charge me more then market rate then I would likely get rid of one of the cars and go back to 1 electric and 1 gas car thus lowering electric car adoption.

    1. Tom says:

      Generally speaking, energy produced during peak usage periods produces more carbon emissions that off-peak energy. At night, there may be excess generation to the point that charging overnight causes zero emissions.

      Charging a little above the market rate for electricity is still going to be much cheaper than burning gasoline and is more sustainable as EV use increases.

      Is there a reason you can’t charge both cars at home? My wife and I have three EVs and charge them all at home. Although we try to stagger the times do reduce our impact on the grid, at night our energy use is low enough that we have plenty of capacity at the panel to charge two, or even three, cars at once.

      1. JP says:

        “Generally speaking, energy produced during peak usage periods produces more carbon emissions that off-peak energy. At night, there may be excess generation to the point that charging overnight causes zero emissions.”

        I’m not sure this is accurate, and is somewhat location dependent. Any new load on the grid means generating output has to increase. During the day that’s likely going to be from an NG plant. At night those plants are dialed down or taken offline. Coal plants are also dialed down but if you charge at night they will be dialed down less, hence more coal is used, which is not as clean as NG. Of course if you are in an area of excess night time wind production things change. In an area of excess daytime solar production then daytime charging would be cleaner, but at this point in time I’m not sure any location fits that profile.

          1. JP says:

            What I didn’t see anywhere in that link is data that backs up the claim that charging a vehicle overnight from coal lowers emissions. Just because the utility offers lower rates for power doesn’t mean that less coal is being burned. They have unused capacity they’d like to get revenue from so they offer it over night at reduced rates. I suppose there is some degree of efficiency gain by running a coal plant at a higher percentage of it’s rated capacity, so maybe there is a slight gain with a greater overnight load in that sense. I’d like to know the physics behind the claims that either charging from a coal plant at night vs during the day has lower emissions, or that charging from a coal plant at night vs an NG plant during the day has lower emissions. Generating output has to match demand, so it’s not as if coal plants keep running full steam at night and somehow dump electricity into the air or ground. 20kWh’s of EV charging should take the same amount of fuel day or night. I have done a lot of research on the subject and have not found anything that contradicts that premise. I would be happy to be proven wrong with solid data.

          2. Tom says:

            The blog points to a possible source of data from a UC Davis study. http://www.its.ucdavis.edu/?page_id=10063&pub_id=1911

            This is a good read: http://energyenvironment.pnnl.gov/ei/pdf/PHEV_Feasibility_Analysis_Part1.pdf

            But your real issue is about the cost of workplace charging. It would be great if your company wants to pay part of your electric cost by charging you less than the daytime rate they pay. I’m all for that, but I’m not sure that’s going to be sustainable as EV popularity grows.

          3. JP says:

            Sorry for the confusion, I’m not the original anonymous poster, so I’m not concerned with the cost of charging, just trying to get a good handle on the real emissions profile of day vs night. (I’m JRP3 from the TMC forums)

          4. Tom says:

            Oh, I see. I had missed that. Thanks for pointing it out. As you may have figured out, I’m tomsax on TMC.

          5. JP says:

            So after looking through all the links I still don’t find anything that suggests night time charging is necessarily cleaner. I’m afraid that is a mistaken idea tied to the erroneous belief that power plants are producing excess, unused power at night. I have heard that in some cases utilities may pay industries to take excess power at night instead of reducing output below a certain level but I don’t know how widespread the practice is, or even if it’s true.

  17. Lanny says:

    Excellent analysis Tom. Given that most EV charging occurs at home and most driving is the daily commute, workplace charging is the most effective allocation of “public” EV infrastructure. One example of this Goldilocks approach that you advocate is at SLAC National Accelerator Laboratory in Menlo Park, CA. Employees and contractors can pay a flat fee of $15 per month via automatic payroll deductions for a permit to charge their plug-in vehicles at one of 16 120v power outlets located around the facility. In addition, there are several Level 2 charging stations at the lab. Thanks for publishing this common sense explanation and recommendations for a simple, affordable and effective plan for workplace charging.

    1. Tom says:

      Thanks, Lanny. It’s great to hear a success story using this scheme.

      1. Robert Winfield says:

        there is an ongoing project with 8 110v plugs at NIH (National Inst of Health) in Bethesda Md since June, 2013. It has been successful to the point of extremely oversubscribed with probably 40-50 EV and PHEV on campus, mostly Leaf, Volt, Plugin Prii, a pluging Fit, i3 BMW and 2 tesla (which dont plugin). As a federal facility, we are NOT allowed to give free electricity so the demo project is presently fully funded by our NIH federal credit union. We suffer from the “free” electricity and primium parking spaces and 6 times the number of plugins as opposed to stations. Right now there is a “How to proceed” as the funding is running out in the next 1/2 year or less.
        The facilities person really needs educated input from real world experience.
        if you could contact I can pass info along to the person in charge so you can talk directly
        winfielr@mail.nih.gov (I hesitate to put the contacts email here)

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