Charging an Electric Car

[JayG]

Hi.

I am starting to think about buying an electric car. So I'm wondering, how much power does a full Level 2 charge use?

I've had a 12KwH solar system installed since 2015 and I tend to produce about 15 mW per year.
Of that, I overproduce anywhere from 1 to 3 mW.

I don't drive much - maybe 3000 to 4000 miles per year on the car that a new electric would replace.
I suppose if I can drive for free (or close to free), I'd use the EV more so maybe I'd drive up to 5000 miles per year.

So I'm wondering if I'd be able to run an electric car for next to nothing, since my only benefit from the overproduction now is the $150 or less that the utility pays me every year to buy back the excess power.

Any thoughts from someone who has both Solar and an EV would be greatly appreciated. I'm in a suburb of NYC if that makes a difference.

[J.P.M.]

You have a 12 kW PV system, not a "12KwH (sic) PV system.

I don't have an EV yet, but the preliminary #'s are pretty straightforward for a back of the envelope estimate.

Depending on vehicle size, driving habits and the weather (A/C and heater use included), an EV might be expected to get about 3 miles per kWh of battery capacity +/- some, perhaps more for smaller vehicles and probably less in very hot/cold weather.

For a rough approx. of a vehicle's possible miles driven per kWh of battery capacity used, take the published estimated range of the vehicle and divide it by the vehicle's battery capacity in kWh (not kW BTW).

A level 2 charger in your garage might be expected to be, as a 1st approx. about 90 % efficient.

So, if a vehicle's estimated range is, say, 200 miles and it has a, say, 70 kWh battery, you might plan on driving 200/70 = 2.86 miles for each kWh of battery capacity used.

Assuming, as a very rough 1st approx. that a level 2 charger might be about 90 % efficient , driving 5,000 miles/yr. and using the above rough numbers will require (5,000/2.86)/0.9 ~ = 1,943 kWh/yr. of electric energy.

Your mileage will vary.

[SunEagle]

You can follow JPM's estimation but it really depends on the EV you decide to purchase. Some of the small ones charge up pretty fast. Others take more power. Each manufacturer should provide an idea of what it takes to charge X% of the EV battery based on your estimated usage.

[solardreamer]

Mainstream L2 home charging stations (charger is actually in the EV) can charge up to 9.6kW (40A@240V). Since you are overproducing, the financials most depend on your specific rate plans and when you charge. If you have a good time of use rate plan with net energy metering and you only charge during off-peak periods then you could very well charge to your EV for very low cost. I charge overnight with solar production covering most of my usage and I had calculated that I was paying about 1/5 to 1/4 the equivalent per mile energy cost for my EV compared to my previous gas car.

[JayG]

Mainstream L2 home charging stations (charger is actually in the EV) can charge up to 9.6kW (40A@240V). Since you are overproducing, the financials most depend on your specific rate plans and when you charge. If you have a good time of use rate plan with net energy metering and you only charge during off-peak periods then you could very well charge to your EV for very low cost. I charge overnight with solar production covering most of my usage and I had calculated that I was paying about 1/5 to 1/4 the equivalent per mile energy cost for my EV compared to my previous gas car.

I haven't actually paid for electricity since early 2016. The way my plan works is that all the power I produce goes into an "Energy Bank" of kW that I then draw from as I use electricity. Since the Spring of 2016 (my system was installed in December 2015 when production was low), my bank balance has always exceeded usage, and I typically have anywhere from 800 kW to 2500 kW at the annual reconciliation, which I get paid for (at a very low rate per kW).

So as long my extra usage to charge an EV doesn't exceed my overage for the year, I can run an EV for almost free (really the amount of money I'd no longer get since I'd no longer sell any excess power back to the utility). I'll need to research specific cars as outlined in the previous replies. The replies were helpful so thanks, everyone.

[JayG]

Mainstream L2 home charging stations (charger is actually in the EV) can charge up to 9.6kW (40A@240V). Since you are overproducing, the financials most depend on your specific rate plans and when you charge. If you have a good time of use rate plan with net energy metering and you only charge during off-peak periods then you could very well charge to your EV for very low cost. I charge overnight with solar production covering most of my usage and I had calculated that I was paying about 1/5 to 1/4 the equivalent per mile energy cost for my EV compared to my previous gas car.

Just curious - which car do you have and what kind of range do you actually get?
Also, how long do you have it and how much lower has range gotten over time?

My hesitation about going to an electric car is range, and I'd be afraid to take it further than 20 miles from home for fear of running out of charge.
It's not like a gasoline car where you find the nearest gas station to fill up. I'd need to get into the habit of charging every night to make sure I have the full range available to me every day.
It would certainly take a lot of getting used to.

Also, I tend to keep my cars for a long time (20 years or longer) and I'm concerned about range when the car is 10+ years old.

[solardreamer]

Just curious - which car do you have and what kind of range do you actually get?
Also, how long do you have it and how much lower has range gotten over time?

My hesitation about going to an electric car is range, and I'd be afraid to take it further than 20 miles from home for fear of running out of charge.
It's not like a gasoline car where you find the nearest gas station to fill up. I'd need to get into the habit of charging every night to make sure I have the full range available to me every day.
It would certainly take a lot of getting used to.

Also, I tend to keep my cars for a long time (20 years or longer) and I'm concerned about range when the car is 10+ years old.

I have have/had multiple: Mercedes B250, Chevy Spark EV, Tesla Model 3. I usually get between 3-4 miles/kWH. It's easy to get into the habit of plugging your car in when you park at home. Much less hassle than going to gas stations. And no oil changes or smog checks. 20 miles is no concern for recent models. Many have 200+ miles range now. Longevity remains to be seen.

[organic farmer]

Just curious - which car do you have and what kind of range do you actually get?
Also, how long do you have it and how much lower has range gotten over time?

I have a 2017 Prius hybrid. So far we have not seen any decrease in EV range.

[jflorey2]

Any thoughts from someone who has both Solar and an EV would be greatly appreciated. I'm in a suburb of NYC if that makes a difference.

We have two EV's (a Prius Prime and a Tesla S) and a 10kW solar system. We still generate more than we use. The Prime gets 4 miles per kwhr and the Tesla gets 3 miles per kwhr. I drive about 4000 miles a year; my wife does about 8000 miles a year.

[Warren93nature]

We have two EV's (a Prius Prime and a Tesla S) and a 10kW solar system. We still generate more than we use. The Prime gets 4 miles per kwhr and the Tesla gets 3 miles per kwhr. I drive about 4000 miles a year; my wife does about 8000 miles a year.

That's really awesome, obviously, the generating is efficient.

[peakbagger]

I have a Rav 4 Prime SE plug in hybrid.. Its about 16 KWhr battery capacity. The internal charger is 3.3 KW max (certain XLEs can have a 6.6KW charger). I have a hybrid solar system with excess capacity and net metering. I can either plug directly into my hybrid system inverter with a 120 Volt plug 12 amp plug or plug into 240 VAC plug in my garage. My utility does not have incentives for off peak charging and even if they did I am not sure it would apply to me since I have net metering so my net power usage is less than my generation. I can plug directly into the inverter to charge with a 120 VAC EVSE or plug in my garage and pull down my battery or plug into a 240 VAC outlet in my garage.

I added the hybrid inverter and battery about the same time I got the Prime. Its one of the DC Solar systems with 2500 watts of panels. Its not optimally oriented but it looks like its offsetting the EV use.

[DanS26]

I bought an EV about three years ago. My main consideration was that it had to have a 300+ mile range because I drive to to a large metropolitan area 75 miles away two or three times a month. So far I have driven the EV 21,579 miles and have recorded an average usage of 2.74 miles per kWh. Now I use and abuse this EV battery.....charging to 90% and discharging to 10% almost every time I make my trip to the city. I drive fast and I like performance.

My battery has degraded ~8%, a little more than expected but as I said I abuse this battery. I have only used a fast charger once and that was only to find out how the process worked. I have self installed two L2 chargers in my garage and a 14-50 outlet.

I have to say my EV experience has exceeded my expectations by a long way. My only comment to the OP is that you do not operate any ICE or EV for free....there is a cost to own and operate any vehicle. My cost to own and operate my EV is ~$0.50 per mile and that includes depreciation, energy, taxes, insurance, wear items, maintenance, battery degradation. There is no free lunch. Having said that, my savings on gasoline alone has been $2,689 to date and that will be increasing dramatically in the future.

Good luck with your decision.

[Ampster]

I have two EVs and have been driving EVs for ten years. In that time I would guess I have driven over 200,000 miles. Due to rate changes by my utility I charge more often from daytime solar when convenient.
Range and lack of DC fast charging was an issue on my first EV but it only had a range of 120 miles. I was fortunately able to trade it in on a Tesla MX that had free DC fast charging for life and range of 230 miles. It currently has 105,000 miles and I have taken it on numerous road trips with no issues.
That 200,000 miles has saved me $24,000 in gasoline over that time.

[Ward L]

I have excess solar power too. I replaced my propane heater water heater to a high efficiency electric heat pump and saved about $800/year. I charge my Tesla Model 3 with the fancy pants Tesla wall charger. This charger will go to 48 Amps and 240v to charge at about 45 miles/hour. I've realized I don't need the high charge rate because I have all night long, so I set the charge rate to 24 amps and charge it up overnight at 25 mph. It is supposed to be easier on the battery to charge at a lower rate. I would have been better off to just install a 14-50 power receptacle than install the Tesla wall charger. I have 43,000 miles on the Tesla and have used about 12,600 kWh to charge up. 12,600 / 43,000 = 0.29 kWh/mile. I've saved about $7k in fuel costs with the Tesla given my excess power. The EV won't take that much getting used to. They are amazing cars and I would never buy an ICE vehicle again.

[foggysail]

I have a question for those of you enjoying electric vehicles. I frequently see environmental reports about supposed cost benefits for electricity ($0.10-12/KWH) and that really surprises me. How much are your real cost for charging electric vehicles???

My reason for question is, I pay only $0.12 now until my contract expires here in Massachusetts. But there are numerous other charges I and my fellow Eversource customers get billed. Eversouce (the supplier) has a host of small charges that they bill as ''delivery fees'' and that cost is higher than the product cost. Without going to my desk to share with all the actual charges, I remember deliverery to be about $0.14/ KWH bringing my usage cost to $0.25-0.26 for every consumed kilowatt hour.

And to make matters worse, our governor....and no, not a Democrat recently signed into law that electric companies....I think starting in 2025, must add 3% renewables to their product EVERY YEAR! Some years ago, Massachusetts was known as Taxachusetts, I don't know what the new slang name will be but someone certainly will come up with a good one.