Lessons Learned From 6 Years of Workplace Charging


Charging a Chevy Volt at the Workplace

Charging a Chevy Volt at the Workplace

More than 60 companies have signed up for the DOE’s Workplace Charging program. Collectively they are installing electric vehicle (EV) charging at more than 150 worksites.

Why Have Workplace Charging

Most companies don’t provide free gasoline for their employees, so you may ask why they would have any interest in providing electricity for plug-in cars. Here are a few reasons: This could help them attract and retain talented employees that adopt new tech, people that could help the company “see around the corner” and be a market leader. Second, especially when combined with solar carports, EV charging can greatly reduce the carbon footprint of the worksite. Additionally, this can be great PR for the company as an environmental leader. Workplace charging is encouraged by the DOE because it has economic, environmental, and national security benefits for both the employees and the companies that provide it.

Having charging stations at work means that employees that don’t have access to charging at home, can charge up during the workday and leave with a full charge for their driving needs. It also allows employees with short range PHEVs to drive home on electricity, rather than gasoline.

Either as part of the DOE program or not, many workplace charging stations are currently being deployed. In some cases, they are running into complications as demonstrated by the recent “Charge Rage” story. The DOE site has case studies, EV 101 guides, employee survey examples, and much more. These can be very helpful, but I thought I’d share my experience from the perspective of an EV driver that has been charging at work for several years.

*Editor’s Note: This post originally appeared on Patrick’s “Cars With Cords” blog.ย  You can check it out by clicking here.

Six Years of Workplace Charging

My worksite has had charging stations for 6 years. During this time we have had a few missteps and we are now on our 3rd charging station provider. I’d like to offer up the lessons I’ve learned from 6 years of workplace charging.

My employer (whom I am not speaking for) is a major high-tech company with offices and factories around the world. They installed charging stations in the late ’90s for the EV1 generation of cars. Then in 2008, they dipped their toe back into the pool of workplace charging. And finally, in 2013, they began a nationwide deployment of workplace charging at all their major US sites.

Level 1 Charger

Level 1 Charger

Let me paint the picture of how this six year journey began at my worksite.

Cheap And Easy

In 2008, the local utility company, Portland General Electric, had a program to encourage workplace charging. The utility paid for the installation of charging stations and for 3 years of renewable energy to power them. The Oregon campus that I work at happened to be the lucky one to get these charging stations. Four Level 1 charging stations were installed and eight EVs could charge at once.

In 2008, EVs were a rare sight. Among my EV driving co-workers’ vehicles there was a Gizmo, a Sparrow, a Xebra, and a couple conversions. The spots were about 50% utilized and you could always find a parking spot there in the far corner of the parking lot if you needed to plug in. The eight EV reserved spots might have even outnumbered the EVs in the parking lot on most days. EV charging was free and easily accessible. So far so good.

Nissan LEAF and Chevy Volt Start the EV Party

Nissan LEAF and Chevy Volt Start the EV Party

Welcome to the Party

In 2011, things changed. The Nissan Leaf and the Chevy Volt hit the streets and they were popular around here. Suddenly it became harder to find a place to plug in. The rare EVs, that were previously lonely in the far corner of the parking lot, now found themselves in a popular place.

Circuit breakers in the charging stations started to overload on a routine basis. At the same time other worksites were clamoring for charging infrastructure of their own. It quickly became apparent that the company needed a plan for workplace charging that would be comprehensive and could be used at all major sites.

Pilot Program

This kicked off a new phase in this workplace charging story. The facilities leaders decided to run a pilot program and learn a few lessons before spending millions by deploying stations across the country or around the globe. Because my campus already had the wiring run for charging stations, we were selected for the pilot.

The old charging stations that had been given to us in 2008 were removed. These didn’t have the J1772 connector that modern EVs needed and they didn’t have a method of collecting fees. One rule that management established for the pilot and any following program is that car charging would NOT be free. As you can imagine, after having free charging for 3 years, some people were unhappy with this change. The wisdom of this decision only became apparent later.

The new charging stations were installed. We went from having eight Level 1 charging spots to six Level 2 stations. We went from Free to $1.20 an hour.

The 2011 Nissan Leaf and Chevy Volt only had 3.3kW chargers. Electricity here is about 10 cents per kWh. This means that these EVs were only able to soak up about 30 cents worth of electricity per hour. Being charged four times the market rate for electricity was not pleasant, especially at work. Yet this was competitive with local public EV charging rates. Blink stations in the area were $1 per hour.

The result of this high price (relative to home charging) was that the utilization again dropped to around 50%. Other than an early morning usage spike, you could find a charging station any time after 10 AM, if you needed one.

The fact that we were charged by the hour meant that there was motivation to go unplug and move your car after it was done charging. This helped clear up the parking spot for someone else that may need it.

Data was collected, usage patterns were analyzed, users were interviewed, and the pilot ended at the end of 2012.

National Rollout

Electricity is Cheap in Most US States

Electricity is Cheap in Most US States

The new nationwide program had been determined. The charging station provider and pricing had been determined. Installations at every major campus would begin in 2013.

Rather than paying by the hour, as we did in the pilot, the user surveys showed a strong preference to be charged fees by the kilowatt-hour (kWh). This seemed like a more fair scheme since we were only being charged for the energy that we used, but there were unforeseen impacts (more on this soon).

During the two years that the pilot went on, a lot more EVs had hit the road: the Tesla Model S came out, the 100,000th EV had been sold in the US, and Nissan even celebrated the 100,000th Leaf being sold worldwide. Plug-in cars were real. They were a small but rapidly growing market segment with sales doubling in 2012 and again in 2013. The West Coast states of Washington, Oregon, and California made up 3 of the top 5 for plug-in cars sales, so adoption here was significant.

At my workplace, they installed 11 charging stations in late 2013. This was nearly double the six that we had previously had. This should have improved availability of charging spots. It did not.

There were three reasons it became harder to find a place to plug in under the new program. First, the Leafs and Volts had been joined by Think City, Plug-in Prius, C-MAX Energi, Brammo e-bikes, Tesla Model S and more. Now there were over 60 EVs on campus. Simply doubling the number of charging stations while the number of plug-in vehicles in the lot had more than quadrupled was not enough.

The next two reasons that it became harder to get a parking spot are perhaps even more important than the growth of EVs in the lot. These two are related to the new program’s pricing scheme. We were now being charged 8 cents per kWh. This was cheaper than home charging. This is good for people that cannot charge at home, since they get an affordable place to charge (if they can find a spot). The drawback, however, is that cheaper than home pricing created an artificial demand. Charging at work was 20% cheaper than charging home. Since your car is sitting in the lot all day anyway, some people took advantage of this discount and began charging at work rather than at home for their regular routine. These are people were rarely, if ever, using the stations when they were $1.20 an hour.

The second problem with the new pricing was that there was no incentive to move your car after the battery was full. When we were being charged $1.20 an hour, there was a financial motive to move your car when your charge was complete.

The new kWh pricing removed this motivation. Once the car was full, the fees stopped. When you are at work, you have meetings, projects, email… It is a hassle to find the time to run out to the parking lot in the middle of the day and then find an available non-EV parking spot. And if the only reason you have for doing it is because someone else may need to charge, it is easy to forget.

Our little EV community tried to work together to share our limited charging resources. We encouraged people to use dashboard cards so we could contact each other. We set up an email-list for EV drivers on our worksite. We started a company-wide forum to discuss issues. We made contact lists with our license plate numbers and car description so we could call, text, or email each other if we saw that a car was full and we needed a spot. We established self-regulated AM/PM shifts. This was marginally effective.

The number of people driving plug-in cars onto the parking lot each day continued to grow. And most of these new drivers were oblivious to the communications channels and etiquette that we had established. Some of these new EV drivers were parking their new EVs in the charging spots without even plugging in. This is just where they thought EVs were supposed to park. In a few cases, new EV drivers unplugged other cars mid-charge… None of these acts were malicious; they were just ignorant of the new world of electric fueling. Noobz! ๐Ÿ™‚

Since this is a workplace, the same cars are generally arriving each day. This allows us to find the vehicle owners and gently educate them.

Just as we started making progress, something unexpected happened. Due to a software glitch, five of the eleven stations had their price set to free. Remember, the stations were only 8 cents per kWh to start with. So “free” was not much of a markdown. But a fraction of the drivers responded like starving college students to a free pizza night. Suddenly, it again became difficult to find a charging spot. People were again complaining in our various forums about the fact that they couldn’t find a spot when they really needed it.

Before our little unintended Freakonomics experiment, I assumed:

Assumptions Are Often Wrong

Assumptions Are Often Wrong

  • Well-paid high-tech employees would not be motivated by a few pennies
  • Busy people with demanding jobs would plug in at home because they were more concerned with their time than cheap or free rates
  • EV drivers would be concerned about the growing EV community and only plug in when they needed to regardless of price

Each of these assumptions was proven wrong. Enough members of our little plug-in community followed the economics greedy agent model and caused a shortage of our valuable resource, charging availability. This was disappointing. Because of the ratio of EVs to charging stations, it only took a small number of people changing their behavior to disrupt the availability. This illustrated what a difference a few cents can make.


The part you have been waiting for: if you are considering charging stations at your workplace, here is what I would recommend:

Join the DOE Workplace Challenge

This program has case studies and resources to help with planning. It is good PR to get listed on their Partners page. You’ll be in good company with companies like Coke, Cisco, Google, Facebook, Dell, and others.

Free or Not?

Level 1 EVSE with J1772 Connector

Level 1 EVSE with J1772 Connector

Decide if charging is going to be a free perk or not. If it is free, be prepared to install a lot of charging stations. For some level of future-proofing, I would recommend at least one charging outlet for every two plug-in cars on the lot today. The good news about free stations is that they do not need to be networked or to have a method to meter usage or collect payments. This allows you to install significantly cheaper charging infrastructure such as standard 120V 20A outdoor outlets. Standard outlets are not as convenient as Level 1 units with the J1772 connectors, but when they are free this may be acceptable. Level 1 outlets don’t charge a vehicle very fast, but cars tend to spend many hours in the parking lot at work, so charge speed it not generally important. Here is an example of a Level 1 unit with the J1772 connector. It is less than $350. This unit (pictured above) is portable, but could easily be converted to a hardwired application.

Choose the Price Structure Carefully

If you don’t intend to make charging free, then pricing can be used to deter or encourage charging. I would recommend a rate that is 10% to 25% above the residential electricity rate. A slight premium over residential rates will eliminate artificial demand, while not price gouging people that live in apartments, have long commutes, or otherwise truly need to charge at work.

A slightly higher than home pricing scheme will encourage people who can to charge at home. This frees up spots for people that have a legitimate charging need. Encouraging home charging has the added benefit that it will likely be done overnight during off-peak times. This is better for the grid than daytime charging.

Fees Should Not Stop When Charging is Done

If you are charging fees, and the fees stop when the charging is done, then the cars will often sit there and consume the access to the charging infrastructure, even after they are full. The easiest way to solve this is to charge by the hour rather than the kWh. Most EVs today have 6.6kW chargers on-board. This means they can add about 6.6kWh at most per hour to the battery pack. If the local rate electricity rate is 10 cents per kWh, this would be a maximum of 66 cents worth of electricity each hour. Adding a small premium to eliminate artificial demand yields a price of 75 cents per hour.

Build a Community

My final recommendation is to form an EV community within your workplace. Have a monthly ice cream (or beer) social/fellowship gathering. Establish a place online where the community can discuss issues and share learnings.

Have an executive sponsor for EV charging. Hold a ribbon cutting event to show that this is important. Listen to your EV community. Each workplace is a little different and the program may need to be tailored to best meet the needs of the people that are using it. This also ensures that the money spent on this will be a worthwhile investment.

Listening to this community will have rewards. If the chargers breakdown, but there is no way to report it, they will go unused and the investment was wasted money. Similarly, if the charging stations are under a sap-dropping tree, where no one ever parks, this was a wasted investment. Having a method of collecting feedback will ensure that the stations can be utilized and meet the goals for which they were installed.

Happy charging!!!

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66 Comments on "Lessons Learned From 6 Years of Workplace Charging"

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If I were an employer I would not be keen on any system which encouraged employees to ‘pop out’ to move their car. If they are costing me, say, $50 per hour and it takes, realistically, perhaps 15 minutes or so to move the car and find a new parking spot, then the cost to me far exceeds the cost of the charging. That is aside from the distraction where people are thinking: ‘Is it about time to move my car yet?’ For as the article notes people can’t become surprisingly fixated on a saving of a few cents. In fact I would not waste minimal management time on running such an ancillary service, and would outsource it, with the proviso that it should NOT be by the hour, and so encourage employees to waste my time by moving their car. By the half day might be a different matter, as they could shift it in their lunchbreak. In many areas of the US with hot summers perhaps the advantage of paying for a charging spot could be increased by using solar panels to provide shade, a considerable boon in very hot weather. A company with the concession to provide… Read more »

Wouldn’t it be wonderful if office workers were 100% efficient, devoting every minute of their time to producing profit for their employer?

Well, actually it wouldn’t. That would be one pretty horrible office to work in.

Reality is somewhat different. People chat in the hallway, go to the lunchroom to get a coffee, even go to the restroom. Really, going out to move your car, and simultaneously getting a bit of fresh air, natural sunlight, and a little walk is a good use of time.

That ain’t the way accountants think, and they would much rather have specified downtime for breaks if that is the intention, rather than having some people wandering off because they have electric cars which need moving, and others who don’t.
In any case, in my view the suggestion to simply wire up lots at 110v and not bother charging or moving cars about downthread is a good one, much simpler and with zero administrative costs.

Many states have laws granting a minimum amount of breaks to employees — so it doesn’t matter what beancounters think. (They should be happy actually, not taking any affects productivity, quality, safety, morale…).

Second, if EVSEs are installed properly, their cords reach multiple parking spots, so they can be shared without having to move any vehicle. So no, I don’t think that claiming this would take 15 minutes per employee is realistic.
Heck, a single designated person could just take care of this.

Providing twice as many dumb 120V outlets instead of L2 EVSEs would indeed pretty much eliminate any incentive for sharing, mostly because lots of cars wouldn’t be done charging before the end of the workday at that pace.
One detail you overlook here, is that it’d take at least as much time for every employee to unroll, plug and secure their own portable EVSE in the morning, and pack it in the evening, as it’d take just moving an L2 plug mid-day.

Other drawbacks: power outlets aren’t as safe as EVSEs, are more easily misused, and charging at 120V isn’t as efficient as 240V.

Inefficiency at 110 only applies to Tesla products..(Roadster, Model S, Rav4EV). Other manufacturers seem to have equal efficiency at 110 as on 220. My Roadster even has a loss of efficiency at 220 if charged at less than 30 amps.

The GFCI requirement, satisfied by the recepticle itself (same as in most people’s bathrooms), makes the unit safe, since they trip at 5 milliamperes. This would only cause a problem with a vehicle like my Roadster. Other vehicles would charge successfully through a GFCI outlet. And it would trip if you were in any danger.

Maybe charge point should figure out a way to charge both by kWh and hour. 15c per kWh and then $1 per hour if you’re still plugged in an hour after you’re done charging (the user should have some grace period but not a large one).

I agree Anthony. That’s what I was thinking while reading this good write up.

Thx Patrick. Things are not as obvious as they seem. Lessons learned are a big deal.

Of course the Tesla super charging system is totally counter intuitive to what you have experienced. Tesla was smart to have proprietary plugs.

What a great read! Thanks Patrick. I am an advocate of workplace charging but do not think it should be for free. I have not looked at the economics of this but I would think (for now), the easiest thing to do would be assigned parking with a monthly fee. This would eliminate the infrastructure monitoring cost, eliminate training newbies on parking etiquette, etc. It does not mean that if you want to work out an arrangement with fellow EV friends to rotate the spot, it simply provides some order to the chaos.

I liked the lessons learned on providing the proper load circuit as well. To me, every new building or parking area should invest in at least running the conduit. Calculate what you think you need and the increase the size by 3x. Conduit is relatively cheap and it will not break the bank if you get it wrong, have to reroute, or never use it. The fact is, if you are building a 50-70 year structure, you think seriously about a world where over half to 80% of the parking area has charging capabilities.
Thanks again Patrick!

This is a good writeup Patrick, thanks for the insight. I have one potential snag about the recommended fee structure though. For people that have Teslas and Volts, being able to leave the vehicle plugged in all day has some great benefits for thermally managing the battery temperature in hot and cold extremes.

I suspect that a growing number of EV’s will have this kind of capability given the issues that Leafs saw in the Arizona heat. It would be very prohibitive to leave a vehicle plugged in all day, to use a fraction of a kWh but be charged something like $1.00/hour to do so.

I’m not sure quite how to solve that snag though.

As some added info, my employer recently installed workplace charging. I actually wrote a story on it here a few weeks back. We’re not in a supply-constrained scenario, so I like that we presently have rates that are cheaper than at home, to help encourage adoption.

However, if we ever had a scenario such as the one you describe, then I think rates that are 10-20% higher on a kWh basis than a person’s home would make a lot of sense. I would still advocate against any per hour charge though per my comment above. ๐Ÿ˜‰

Employers could offer both 30A J1772 for $1/hr, AND 120 V GFI plugs for $1/day. PEV drivers could pick what they need.


Guess: Intel?

I’m sorry to hear about your disappointment in your colleagues’ Freakonomics behavior, but remember that working in a large hi-tech company is usually an experience of continuous libertarian-“greed is good” brainwash. I know firsthand, having worked @Intel in 1997-2000. So you are not getting a sample of typical above-average-earning busy professionals.

In any case, on the plus side you did create a community, and arrived at a very keen analysis of how this works. Thanks for sharing. Will your bosses listen to your advice? Or will it have to go through Corporate (i.e., disappear into outer space)?

There’s some good stuff in there, for example the part about not making charging cheaper than at home. One problem I have with the whole workplace charging thing, after myself having employer supplied L2 chargers, is that I think the emphasis on advanced charging is unnecessary right now. Employers, and more likely, the real estate owners they lease from, could afford to place standard weatherproof 110v outlets at a dozen or so parking places and call it a day at this phase of the EV rollout. I’ll list the reasons why this makes sense. 1. You can’t really burn enough electricity to make a serious dent in their budget with a 110v charger. 2. 110v outlets are cheap, and a fairly trivial extension of the existing landscape lighting system. 3. You can deploy enough of them so that it does not make that much difference if people don’t remove their cars after charging, or otherwise abuse the system. 4. 110v charging is adequate to solve most common workplace charging issues. 8 hours of charge is enough to make it home on a long commute or top off the charge for errands. 5. The employer/landlord does not have to get into… Read more »

I like the sound of that set up.
Keep it cheap and simple.

Big problem with the 110v set up is the high current of EV charging can quickly overwhelming the 110v circuits. It’s almost 15amps of current just to supply 1500 watts to the battery.

I’m no EE, but I would have thought that although it is going to cost something, breakers or whatever could deal with it.
What do people do it in their homes?

Here in the UK 240 volts are standard, but with electricity at ~$0.23kwh then it is much more expensive to give it away.

True, but the point being that the cost savings are:

1. using common breakers and plugs.

2. No charger, just an outlet provided (with GFCI of course).

So for example, a building can pull a 150 amp line and feed 10 spaces.

Agreed, and BTW large office buildings typically have 3 phase supply, so instead of “pull a 150 amp line” they might pull a 3phase 50A (208/120) which makes it easy to add a mix of nema 5 and nema 6 outlets …

I was going to say the same thing.  There’s plenty of spare capacity for lots of these things.

Something that a non-EE might miss is that circuits are current-limited by wire size, but insulation might allow substantial increases in voltage.  Switching from 120/208 3φ to 240 volts phase-to-ground would allow all J1772-compatible vehicles to connect, but pump a lot more power over the plug.  Available current could be rationed by “rolling blackout” between connections to equitably share available juice.  That is a strategy for upgrading at minimal expense (no need to dig new conduits) as demand continues to increase.

Without EVSEs, you need to deal with tripped breakers.

An EVSE has a built in soft resetting GFCI and breaker.

Perhaps a super cheap 120v version could be found?

I’m against free charging (and free parking), for all the above reasons plus it encourages people to drive to work by themselves, rather than carpooling/mass transit/biking/walking. But to be realistic, most people will continue to commute via SOV. So what I think would be best is for the company to provide L1s in a gated/segregated area, with people buying monthly/quarterly/bi-yearly etc. passes with hang tags, stickers or a gate-opening card (or else use reserved spaces as mentioned in another post). If the company wishes to provide their employees with a transit per diem (or just include that in salaries), the employees can use it however they please, paying for parking, charging, etc. or just pocket it if they use the lowest cost and best environmental option. This way everyone can make their own decisions on what’s cost-effective for them, without having to run out and move their cars. The biggest problem with only providing L1 outlets is that these receptacles aren’t designed for constant plugging and unplugging, nor are the plugs used with them. For serious use, I think permanent J1772 plugs should be provided, even though it costs more. The company can charge something above the actual kWh rate… Read more »

” L1 outlets … arenโ€™t designed for constant plugging and unplugging”

I think the GFCI in my kids’ bathroom has been handling a hairdryer every day for many years, and if it fails, I can replace it myself very cheaply …

Indeed.  Just swapping out receptacles as they show signs of wear, or even on a schedule every couple of years, would be adequate.  NEMA outlets are under $10 apiece, the labor would cost far more.

The info offered was quite good, as a summary of workplace charging. I would also encourage pricing schemes to also pay off the equipment costs. Davemarts comment on lunch time car movements makes sense too.

That’s another reason installing Level 1, 120v outlets makes more sense for business. Quicker, predictable payback for low expenditure, especially with assigned parking tied to a flat fee. If the EVSE gets damaged, broken, stolen, what have you, it’s the loss of the EV owner and not the business (unless your insurance covers auto burglary in your lot).

Great article, thanks.

I would personally be comfortable if work charges twice the actual rate for the electricity. Realistically, EV owners save so much already (compared to gas) that it should not make a big difference whether you pay $20 or $40 a month to recharge 6kWh every day at work.

Does anybody here have any experience with eVgo? They have a plan that they will install an EVSE at your home for $30 a month. They also offer that at workplaces, but I do not know the price.

I am curious how many people would get their own dedicated EVSE at work for $30 a month, which could be great for your employer also since they did not have to spend any money on the equipment. I guess there might be a contract period and termination fees, like a cell phone.

This is a good article. Many of the consequences are pretty obvious in hindsight. What it boils down to is that people are motivated by their wallets. If something is free they will overuse and abuse it. If it costs them money they will use the resource more wisely.

One the other hand, charging requires metering, authentication and billing. All this leads to much higher cost per EVSE. And, as we have seen with both Blink and ChargePoint, lower reliability.

The approach of 110 outlets has a certain allure. It is pretty cheap, pushes the charger cost to the vehicle owner and does away with the charging overhead. It does require that more plugs be put in and more parking area be allocated to EV charging.

If the use case is just getting from home to work and back, and you’ll be plugged in all day, 120v charging can work just fine. But it also makes sense to have some 30a 240v charge stations available for the times you’ll need to go somewhere mid-day.

If you’re not running up against the limits of 50-60 mile range, slow charging works. But if you are, and the utility of your car is diminished, installing 120v because it’s cheaper is no savings.

Most of the people I know who drive EVs daily, without an ICE backup, want faster charging, not slower.

When sited at the midpoint of four parking spaces (four square) a single 240v charger can more capably service 4 cars for a lower cost than 4 120v EVSE. You also get the advantage of being able to charge faster, for the times when you need it.

Doesn’t that entail specialist charging equipment and add to the employer’s costs?
No doubt that the employee would like charging to be as fast as possible, but from the employer’s point of view the aim is to provide a perk, but do it at low or reasonable cost.

If higher energy density batteries are indeed going to be here shortly in the Leaf, then in any case most users will be able to get to and fro to work quite comfortably, whilst Volt driver’s can always use their ICE.

ECI … there is no cheap one-size-fits-all solution.

You muse about somebody who charges at home, and finds 120V at work insufficient ” for the times youโ€™ll need to go somewhere mid-day”. With all due respect, such a person needs to save up for a Tesla, or stop by a QuickCharge on the way to “somewhere”

I money was no limit, then employers would have a charger per parking space. Since there is no free lunch, the 120V solution is commonly proposed as the cheapest way to expand charging for employees, and it will work for the vast majority of cases, but it does not solve every problem.

Was there ever any consideration to actually assigning spots? If the same people were there every day with the same cars it seems either an assigned spot or an assigned spot for part of the day would be effective and intelligence could be applied based on the amount of charge actually required. The cost could actually be calculated by charge required and charged directly to each employee without the need for “smart” chargers.

Companies which don’t assign parking spaces won’t want to get into the complication of organising allocated parking.

All sorts of considerations of status, what happens about a space when an employee is off sick and so on come into play.

They’ll do it for their top execs but not the hoi polloi.

Dr. Kenneth Noisewater

Chargers should charge at 125% the price per kW of residential power, then switch to $1/hr after charging is complete. Dunno if Chargepoint is flexible enough for this, but it should incent people properly.

Hmmm this could be a problem, let say you charge $0.20/kWh + $1/hr when full …

When the battery is almost full, the car charges very slowly, so it can take up to 2 hours to go from 95% to 100% and during that time it costs $0.20, and it is hard to predict when exactly the car will shut, so you might get a surprise $1/hr penalty.

Also, in your pricing model, when folks charge to 100%, during those last slow hours they occupy a EVSE for a long time, and use it inefficiently.

1) At least on the 2012 Leaf, power remains steady until at most 1/2 h before reaching 100% SoC. The ramp-down is quick and predictable (consistently just under the ETA given by the car, website or app). No issue there.

2) The driver can be notified when charging is complete, either by the car itself, or certainly by the EVSE if it’s fancy enough to have this kind of billing mechanism in place.

Dr. Kenneth Noisewater

Chargepoints can determine when a car’s finished with its charging cycle, and presumably a 15-30m grace period after a ‘charge complete’ message is sent would allow for plenty of time for someone to come and move their car.

Frankly, I’d rather see lots of spaces with 120V 15-20A outlets or L1 chargers, where folks would be expected to park all day. It takes a full work day for a Volt to charge at 120V@12A from empty, and BEVs could easily justify much longer periods. Plus, weather.

It kind of sounds like based off of this story here that under the old system there where eight charging stations and it really didn’t mater to much in that there was no facet that would allow a flood of EV’s to come in. Such as when the Nissan Leaf came out then there was a way for none EV extremists to get hold a EV. As soon as a mass marketed EV hit the roads everyone could now get one and now the once free charging became more of a burden then a green thing. What really should have happened vs playing the blame game on people’s greed over charging is that the bottom line is they should have slowly ramped up the number of charging stations up from the existing six to eight ones to say 14 to 16 a few months later and then raise it 24 to 30 a few months after to keep up with the growth of the local EV heard. In that after a while based on the maximum of electric number of cars that could in theory park in the parking lot you will soon over time reach a maximum number of… Read more »
As ev’s become more and more common, it will not be out of the ordinary to see employee lots with 100 ev spaces. Since the employer is under no obligation to provide ev drivers a special bonanza, 1.4 kw charging rate should be the defacto standard. The 13 kwh used per vehicle for the typical 9 hour work day is something that does not cause undue expenses, and gives more ev employees the chance to charge up, because as with apartment dwellers, most would be happy with any available facilities at all. Its quite unfair to provide highspeed charging to a priviledged few, while the vast majority of ev employees get absolutely nothing. As far as the “high current” gripe of 120 volts, a typical 100 car ev set up would be 1200 amps ostensibly, but arranged as 174 amps on 277Y/480, being fed by a conservative 225 amp feeder. (Weatherproof autotransformer power packs will take care of the final overcurrent/transformation requirement to the individual outlets). Pricing will be easy for the employer, since it will be assumed that if you are parked in this space you will use 13 kwh. Loading will be 100% over the full work day,… Read more »

As evโ€™s become more and more common, it will not be out of the ordinary to see employee lots with 100 ev spaces.

And that could be only a decade away. If you are running the circuit for the lamp post, it seems awfully easy to plan for this if you are working on a new construction.

Along the way, managing the daily demand curve is going to become a factor.  Level 2 EVSE would become essential if the employee parking lot was expected to be the buffer for a heap of rooftop PV; you’d get the bulk of your juice between 10 AM and 2 PM local, and you’d need a connection that can pump it across as it’s generated.

Of course, charging at home overnight is the best situation for baseload.

Dr. Kenneth Noisewater

Ideally, especially in the SW, these spots would have solar canopies to offset power use and provide shade to avoid having to remote start a car to cool it.


For a large site with sufficient demand, I would think an “all of the above” strategy would work out quite well. What I mean is that there should be L1, L2, and L3 available. Lots of 120V 20A outlets available for free. Fewer access controlled and appropriately fee-based L2 J1772 stations, and one DCQC unit if there is a need from the employee population.

Great article!! Your experiences mirror what we have seen in WA perfectly. We do have a lot of people who spend large amounts of their personal time in order to collect $1.50 in free electricity and yes, it confuses me as to why people, many of whom are very highly compensated would choose to use their spare time this way.

the only real comment I have is the ideology of your pricing scheme. It should not be based on the electrical rates. It should be based on the cost of alternative transportation options. I would take a tact of computing the cost of driving a 35 mpg car (generous I think) then base the charging rate on a percentage of that and calculate it say once a year.

after all that; I am in favor of charging by time.
This can be complicated by the fact that there is a wide disparity in charging speeds and one option would be to simply throttle down the stations to a medium of 5 kwh. this still provides benefits to the people who choose to pay for faster charging speeds and might allow more plugs to be installed

Dr. Kenneth Noisewater

the only real comment I have is the ideology of your pricing scheme. It should not be based on the electrical rates. It should be based on the cost of alternative transportation options.

It should probably be at what the market will bear, as judged by utilization rates and congestion. When you’ve got 1:1 between desired users and available spots, your pricing is in balance and correct.

It can be hard to work out the economics of home charging. In California, for example, if you have an IOU (Investor Owned Utility) serving your home, your marginal rates for a kWH can be anything from 10c all the way to 56c/kWH. The municipal utilities are typically near the bottom of this range. Then there’s the capital expense of installing the EVSE, which can vary greatly.

EVs are charging for hours, which gives a very different utilization than a gas pump nozzle, or a Hydrogen fill nozzle. And the EVs are only there during the workday (less than half of the 168 hours in a week).

Well written article….

FREE and CHEAP are the two biggest problems with public charging stations, especially at work.

Charge 150% to 200% residential rate and then charge $2/hr for any “hogging” after charging is full will solve the problem.

Once that happens, ONLY those who truly “need” it will use it.

You can NOT underestimate how “cheap” people are. Many of the EV owners are cheap that is why they bought EVs in the first place….