The Top 3 Ways to Save Money Through Efficient EV Charging


JUL 23 2018 BY STAFF 29

Maximize your charging efficiency, save money, and benefit the environment.

When you bought your electric vehicle, you probably had a variety of reasons in mind, including environmental impact, access to the latest technology, vehicle performance, saving money on fuel costs, and automotive fashion trends.

There’s another potential benefit that many people don’t often realize: charging efficiency. Not all outlets are the same. By maximizing the efficiency of your charging, you can actually increase your fuel savings and potentially the environmental benefits as well.

Understand Battery Charging

The basics of battery charging are the same, whether you’re charging your car or your cell phone. Your car may use a lead-acid, nickel metal hydride, or lithium-ion battery, but in all cases, the concept is the same: Passing an electric current (from mains power) through the battery causes a build-up or “charge” of electrons at the negative end of the battery, known as the anode.

Like people in an elevator, the electrons want to spread out evenly, which means they want to

get to the positive end of the battery, the cathode, but the only way for them to get there is if you activate the circuit for the system that you want powered—in this case, your car.

When you want to recharge a battery, you apply electricity to reverse the flow of electrons back to the anode, essentially resetting the battery to its original state. However, there are many inefficiencies in this process that result in a less than ideal charging experience. In particular, the chemical process also causes insulating atoms to form and obstruct the electrodes. Therefore, we can increase the efficiency of the battery with some targeted charging practices.

1. Maintain Ideal Charging Conditions for Batteries

The major costs of batteries are their purchase price (and thus their lifespan), and their efficiency with different types of charging and discharging behaviors. By taking steps to prolong your battery life and use only the most efficient charging behaviors for your EV’s battery type, you can save a significant amount of money in the long run.

Lithium-Ion Batteries

This is the standard battery type for modern EVs. For the most efficient charging, including longer battery life, there are two important things you need to do:

Keep the battery as cool as possible. Park the car in a garage or carport, and don’t charge in open sunlight if you can help it. Instead, choose indoor or covered charging slips, or charge when the sun’s not out.

Keep the battery charged in the range of 30% to 80%. Try not to fully drain or fully charge it when you don’t need to. In other words, you can randomly charge this battery at various intervals without worry. In fact, it’s preferred!

Fast charging is a good option for lithium-ion batteries.

Lead-Acid Batteries

According to Battery University, the best way to prolong the life of this type of EV battery and charge it more efficiently is to avoid heat where possible. Like with most other batteries, heat is an efficiency killer.

Do not allow the battery to completely drain on a regular basis, but do fully charge it each time.

Do not attempt to fast charge this type of battery.

Nickel Metal Hydride Batteries

This battery can form a memory, so fully charge it each time, and give the battery a full discharge around every month to three months.

Do not allow the battery to overheat while charging.

Fast charging is a good choice!

2. Use a Smart Charging App

In order to get the most savings out of your time at the charging station, be sure to use a smart charging app. Modern batteries and EV computer systems are much more sophisticated than “charge goes in / charge goes out,” meaning that smart software will do a better job of managing all those little technical details.

As a bonus these apps will tell you where the nearest charging stations are, meaning you won’t waste any time or money driving around looking for one.

3. Be Deliberate About Which Power Sources You Use

The money you save on gasoline with an EV is offset somewhat by the money you spend charging your car, in the form of higher electricity bills at home and any costs you pay at commercial EV charging stations. There are two things you can do here to save money:

Charge from the Cheapest Power Sources

This takes a little bit of planning, but once you figure out the optimal routine it gets easier. Basically, what you want to do is figure out how much it costs you to charge your car at home and at any commercial charging stations you use. Then, charge as much as possible at the cheapest power source. Only charge from other sources when you have to.

If you have a car with an auxiliary gasoline option, be sure to take into account things like elevation changes and traffic commute times in your morning versus evening commute, so that you can choose to use battery power in such a way that you’ll only need to recharge right when you get to your preferred charging source.

Install Renewable Power at Home

If you own a home, you can reduce your EV fuel costs potentially all the way down to $0 by installing solar panels or a wind turbine on your property. These renewable power sources only work when the sun is shining or the wind is blowing, but during those times they tend to produce a surplus of power.

Most power stations will pay you a rebate for any energy you contribute to their grid, but the rebate will almost always be less valuable than the amount of money you’ll save by charging your EV during those surplus times. In fact, charging your car with solar or wind power is one of the most cost-saving and greenest solutions available to you today.

4. Keep Your Vehicle Serviced

Cars lose a lot of efficiency when they’re in poor repair. A well-serviced vehicle with an efficiently running electric engine is going to much less wasteful on the battery, meaning you’ll get more bang for your buck on a given amount of charge. Take your car in for regular service, and at home make sure your tires are properly inflated, and keep excess baggage out of the car.

Keeping the electric motor and battery themselves in good repair is also important. Most electric vehicles have an optimal conversion rate of around 80 to 90 percent, meaning that 80 to 90 percent of the energy drawn from the power grid during charging will actually be converted to usable energy for your vehicle. Maintaining the electrical system will ensure that your conversion rates remain high.

BONUS: Free Charging Stations

If you happen to be traveling past a free charging station, the money you’ll save by charging for free could be well worth the investment stopping for a few minutes to top off.

As an added bonus, by familiarizing yourself with the locations of available charging stations in your area, you can save yourself time and stress whenever you go on a road trip to new locations on a relatively low charge. Getting to better know the various parts of your town or city means you’ll discover some hidden bargains!

Written by Jordan McDowell from EV Connect

Categories: Charging, General

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29 Comments on "The Top 3 Ways to Save Money Through Efficient EV Charging"

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“If you own a home, you can reduce your EV fuel costs potentially all the way down to $0 by installing solar panels or a wind turbine on your property. ” *lol*… the only way you can get it down to $0 is if you make sure that the neighbor install and pay for it, including the cable that you need to connect to his installation. 😉

But with enough subsidies of different kinds you can sometimes reduce the cost at least. 😛

Here in the US with the national average of 11 cents/kWh, one can generally cut the cost in half for 25 years and that is a whole lot of savings. With those savings, some like to say at some point the cost is $0. Depends on a lot of factors but I paid for my system in savings after 11 years. Currently, I am no longer being supported by an aggregator so I only get wholesale pricing of 4.5 cents/kWh for what I put back on the grid. I also have to pay a $15 monthly fee for the privilege of having a utility meter. Still, in the hot AC season, my power bill is averaging $30/month and that counts my EV miles as well so once the system is paid for the $0 argument can be made.

How much did the system cost? And how much do you save in electricity bills per year?

All pvs have a payout period after which it’s all free electricity and fuel. So one actually can fuel for free. It makes no difference what the upfront cost is as long as it’s fully recovered while you live there. I save about $3k/year in electricity and fuel costs and have extra juice for another ev, coming soon i hope. Ask me again in 5 years and that will be higher, it’s not like electric rates and gas get cheaper in the long run.

What was the upfront cost in your case? It makes all the difference.

Most were early adopters who got the needed subsidies to offset early adoption. The more relevant question is what is the current upfront cost with and without subsidies. See answer below.

$12k after credits for 5.4kW. What you pay upfront is irrelevant if the risk of losing any of that money is 0. Think about it this way… it’s like putting your money in a vault, a few years later you come to pick it up… and few years after that you come to pick up some free money. Of course, what you get back will vary depending on your location. In CA is just ridiculous how fast the payout is these days.

6kWp array that generates about 9000kWh annually. At 11 cents about $1000 per year savings. DIY solar kits complete in the US sell for under $2/watt. Currently, a 6kWp array kit can be purchased for under $12,000 so 12-year payback with no subsidies, thus my half of 25-year statement (without subsidies). Now there are still 30% federal subsidies so payback is shorter than that. The hardest part of a solar installation is mounting the boots on the roof or mounting the posts in the ground. The rest is brutally simple. All kits come with the necessary engineering stamps. Your house drawings have the engineering stamps for rafter weight loads. If you have an older house without this information add another $500. We require a certified electrician to hook to the panel which consists of connecting an L1, L2, (the black and the white wire) and ground wire. Honestly, wiring a three-way light switch is harder. I’ve installed a lot of projects, but solar + EV is by far the most rewarding.

9000 kWh, then it’s in a pretty good location. That is close to the upper limit. So that 6 kW array installed would be ~$18 000. Assuming an alternative investment cost of 7% (pretty standard and something you would do by just using index funds, but very low if you were running a company, then 12-15% would have been more normal). Then you will never ever break even…. Assuming $12k and that you do all the work for free (not that the world works like that in general) and you would have a payback time of 25 years. That is of course assuming that you don’t put anything back into the grid for those 4,5 cents having to pay $15 per month to do so. Those $15 per month and a few kWh put out into the grid are basically enough to make sure that your investment never pays off. But not everything is done with profit in mind, thankfully. And economically it is smarter than buying an EV (or any car) which is just a big money waster. Anyway, the “electricity for free” statement in the article is so dead in the water that kids would think that fish… Read more »

What you are missing is that the “free money” argument comes mainly from CA and the southern states where the conditions for pv are perfect. My grid connection fee averages about $8/month. Regular electric rates were about 25c/kWh including all fees and taxes, before pv. In a hot climate like ours $2000/year bills are common (and kinda low). Gas prices are $3.5… for now but soon in the $4s to be sure. Electric rates (SCE) are on a schedule to increase each year until 2020… for now, more to come i’m sure. In CA and much of the US we have NEM where what you put into the grid you get back later so no loss there. Install costs are high in US but much lower in EU… which i’m guessing is your part of the woods.
Your investment advice is just laughable, i guess another fleecing 2008 style is required to remind people there is no free lunch on the stock market…btw, i trade daily on the ARCA and CFE.

It was not an investment advice, as said you can reduce the cost with enough subsidies (not paying taxes, NEM, FIT etc.). And in some places it is starting to get close to profitable without most subsidies. It would still very rare be a good investment considering how little the return still is.
Investments with possible profits decades away are generally frowned upon, as you probably know. But there will always be exceptions where it can be a good investment, in the future it might even become the rule instead of the exception.

And even if and when it is profitable it is never “free” like the article stated.

Interesting that you included the alternative investment cost and made no adjustment for the cost increase of electricity over time. And your 7% is adjusted continuously over the breakeven period not invested over the life of the system. Talk about your dead fish swimming.

“Assuming $12k and that you do all the work for free (not that the world works like that in general)”
The two largest home improvement companies in the US are Lowes Home Improvement and Home Depot. Billions are spent each year by people who do exactly that. Home Depot slogan “You can do it – We can help.”

Agreed, Nothing is free!

It’s true, missed opportunities do cost alot!

I’m a little surprised you didn’t mention charging at higher voltage, for example 240V instead of 120V. When using level 2, the car’s BMS and auxiliary systems are only powered half the time. This can result in 10-20% reduction of losses in charging efficiency.

Is there any study done on this i can read about? Link?

Yes, search google for “A comparison of electric vehicle Level 1 and Level 2 charging efficiency” click the link for IEEExplore

Thanks! It’s a bit old, i wonder if anything changed since 2013…

Not only do I not have sheltered parking for my Leaf but my spot is on the South side of the house and the light colored siding reflects even more sunlight at the car. On blisteringly hot days (30C or more) I still don’t read more than 6 temperature bars showing when starting off. I have raised it to 7 with an experimental “hard drive” with the a/c on. Short DCFC top ups usually add one bar to what’s already there but I’ve never done a DCFC to low battery to 80% to find out what would happen. In hot weather when I come in off a highway run was my 19 year old gasser I raise the hood to let the heat escape and prolong the life of the lead acid battery. I just had battery #3 installed this winter as it was starting to struggle with the -30C temps. Battery #2 had lasted an incredible 11 years. Advice about over heating batteries and not charging li-ions to full if not needed should be well taken. This might be why my no tms battery pack is holding up so well. I learned these things from Inside EVs. thanks you.

If one’s time is worthless, one can get Leaf/i3/Maven Bolt and wait at DCFC for other free charging Leaf/i3/Maven Bolts.

Are u going to bitch about this for the rest of the year now?

The free charging is a problem. You don’t want to charge during peak times just because it’s free. Also it contrasts with your point about charging when it’s cool/shaded.

Free charging can’t go away soon enough. It encourages the wrong behavior.

I would allow for free charging during the solar surge hours between 10am and 2pm. This could actually help in stabilizing the grid.

Agree pretty much with everything said in the text – one thing he didn’t mention is FOR SOME, time-of-day metering makes sense – where you can decrease the cost of recharging your vehicle between 11 pm and 7 am – which fits fine into most work schedules.

In my area, almost no residential (“domestic”) customers take advantage of this (neither do I for reasons of net metering complications), but it is very popular with small to medium size commercial customers and mandatory for larger ones. But the savings are real.

My after tax cost of my so-called 9120 watt, 9000 kwh per year system (Buffalo gets as much sun as Alaska) was $8605. Even though rates are cheap, I’ll be able to recoup my investment in 8-10 years. One of my wiser investments.

I have a few problems with this article:

1) Fast charging is harder on the battery, shown in a study of Nissan Leaf by NREL. Not a lot worse, but worse.
2) Jeff Dahn stated that charging to 70% is his recommendation if you don’t need more charge. Even less is better. I charge my Tesla Model S to 50% every day except Saturday when I charge to 70% because I need additional range
3) Still looking for the reference, but I recall Jeff Dahn saying that going a lot lower than 30% is not a problem for a Lithium ion battery.
4) Keeping the battery as cool as possible is only significant for BEV without TMS (like the Leaf I used to own). My 4 year old Tesla spent its youth in Nevada with another owner and after 60,000 miles only lost 5%.
5) A “properly serviced electric engine”??? You have to be kidding me. No service needed for the motor unless something goes horribly wrong.

Charging only to 50% seems way over the top. Even at 70%, the battery is likely to degrade much more due to ageing than due to cycling…

As for fast charging, results are inconclusive AFAIK. It’s surely bad for Leaf; but it might actually not be bad for batteries with active TMS. According to Jeff Dahn, slower cycling in fact results in significantly lower cycle life — though I’m not sure how this translates to real-world use patterns…

It isn’t way over the top when there I start with 124 miles of range knowing that the chance is 99.99% that I won’t drive more than 40 miles that day. Calendar aging doesn’t seem to be much of an issue given the tiny loss of capacity after 4 years and 60,000 miles.

Here is the reference to discharging Tesla to 5% not causing any harm: Let me quote Professor Jeff Dahn who is now working with Tesla on battery development I just had an interesting email exchange with Professor Jeff Dahn from Dalhousie University in Canada, who’s a Lithium Ion battery expert (you can google his name or search him on YouTube and find his lectures). As a side note, one of his former Ph.D. students is now in charge of battery lifetime at Tesla. Jeff’s advice, which he was generous enough to give freely, and which I think comes with a great deal of authority, is this: – In general, charge the battery to 80% unless you need more for a long trip. In fact, he said, 70% would be even better (the lower the upper cut-off voltage the cells see, the less electrolyte oxidation there is and the longer the lifetime will be). – Discharging to 5% state of charge (95% discharge) doesn’t harm the battery either. Discharging all the way, which could be damaging, is actually prevented by the Tesla pack control electronics. (I do know that Tesla advises against letting the battery charge run too low. I’m… Read more »

What we should add for No.1 is to keep it within that 30 – 80 percentile, but at nights below 10C, have it trickle charge to 100%. It would get some cell balancing action and keep the cells warm.

Drawing high amounts of amps from a freezing battery can cause dendrite build up. Unlike sustained high temperatures, which can cause cell unbalancing and heat damage.