Charging (In)Efficiency

I wish the cars could back feed.
We rent but when we buy we will put in solar panels and a battery system. Financially worth it? Maybe, maybe not. But I like the idea I don't need to rely on the grid in the event something goes wrong like winter 2021 when there were mass outages. People also spend money on things like pools which certainly don't save money but they just want them. I have n o interest in a pool but would spend on solar. Each to their own.

I do have a small 2kWh battery (intended for use with my 700watts of portable solar) which was for traveling/camping/outages but decided rather than have it sit there the rest of the time (ie most off the time) it charges up overnight on a timer and during the day is powering my little home server rack which has a NAS, the router, wifi access point and a couple of low power servers in it. It's not worth it financially as the unit was like $1,600 and this saves me 2kWh or around 50c per day, but that's not why I bought it, I just decided to repurpose it. Works well and is a little experiment of how I might use solar and a big battery in future.

I was trying to figure out what it would cost my sister to run an EV back in the UK vs her gas car and the best she can get overnight is half price power like you. So I am sympathetic. Still makes it a lot cheaper than paying for gasoline though, however she will need to wait until something comes along with Peter range than the Mini at a lower price as she lives in a mountainous rural area that gets cold in winter and has a need to do 200 mile round trips @70mph with the only DC fast charger on the trip being about 70 miles from her house so there would be range anxiety in the winter...

 

I don't know how much you pay for your electricity, but the US average is 14.1c.

At 100% efficiency a 75% charge of your battery would cost you $3.06
At 80% efficiency a 75% charge of your battery would cost you $3.82
At 60% efficiency a 75% charge of your battery would cost you $5.10

Assuming you travel 100 miles on 75% of battery (depends on may factors but my wife would get better than that, but just to put a number on it) that's 5.1c per mile @60% efficiency vs 3.1c@100%.

Genuinely a big difference for sure.

But a gas Mini Cooper S takes premium and works out to 12.8c per mile at current US average price and at 31mpg combined.
Even a car that takes regular would need to get 100mpg to match your 60% efficient charging cost.

If you don't like the loss on principle, then a move to L2 will help.
However given that they cost like $300 to buy a 16A one if it improved things from 60% to 80% you'd save 0.8c per mile which would take ~38,000 miles to recoup the money. Granted you'd get faster charging and could leave the Mini charger in the trunk for emergencies, but still...

 

I did some more checking into our charging history...

So back in the first week of December, when it was warmer than it is now, we tested our included Mini charger, which is 120v.
We charged from 55% to 81%. This is 26% of 28.9 or 7.5kWh. The charging history says we used 10kWh. So thats 75% efficient right there.

2 days later we charged on our L2 from 69 to 100%. That's 31% of 28.9 or 8.9kWh. The charging history says we used 11kWh. 81.4% efficient.

Both of those are December nights in an unheated garage so not that warm even in Texas.

 

I am with Gvilleguy, charging efficiency is good to know, and technology will improve. But the savings I get from the SE compared to our previous Subaru Legacy GT is just tremendous, and I will not go back to an ICE. Especially with petrol forecasted to increase to $3 per litre here in NZ.

 

There are several cars in the 25-28k range that claim to get around 50mpg or a bit over, but I'm not convinced they really do.
Just as EPA range numbers for EV's are way off reality for many people, so are EPA mpg figures.

While the Mini Cooper SE with fed rebate is cheaper than them which might make people think it's the economical choice, it's not really fair comparison. The Mini is not intended to be the most economical way of getting around. those cars are larger, which is to their benefit. The Mini is better made though. By far. The Mini is also much. much, much faster. It also handles better. It's apples and oranges.

But you are correct, if we're looking at money only, there are ICE cars that are about the same to buy and get high mpg figures which may make them economically more viable. However we are comparing what sounds like highway use in a very cold winter. In other situations your Mini is cheaper to operate. You have to look at the overall picture.

But to make a more fair comparison of EV over gas you need to compare like for like. So for example a Cooper S gasoline model vs the Cooper SE.
Even without government rebates the SE is thousands cheaper over just a few years. I know because I made a detailed spreadsheet before buying.
With federal and in our case a state rebate, if the battery dies after 8years and 1 day so no warranty, I could literally throw the whole car in the trash and still be financially better off than if I bought gas version. And that's not an exaggeration. I did the math!

But no-one who really cares about the financials should be buying any new car anyway. A 5 year old car with decent gas mileage and reliability that you keep for 2 years and then move on is the cheapest way to go for total operating cost. That's what I did for many years.

 

It’s more about convenience for us. A 27+ recharge mid winter left us “without a paddle” at times when we were ready to use up all of the range. It should be required to build homes with electric in the garage that can support a 32A level 2 circuit.
Theoretically the L2 charger has some inherent value and can be resold down the line.

 

I agree with you that it is expensive. It has been mentioned before, and I have not yet googled the 2022 IRS laws - but IRS form 8911 gets you 30% back on your taxes to a maximum value of $1,000 on the installation of a level 2 EVSE. This year I'm getting back $400 on my $1,400 installation. But anyone thinking about doing this now needs to research if the law around 8911 has changed or not for next tax year.

 

In the scheme of things, the SE's 7.4 kW charge rate is "low and slow". Even the 50 kW DC fast charging is "low and slow". This is another stubborn truism that comes from Teslas that charge at a much higher rate (just like the "charge to 80%" restriction). The SE has to be one of the most forgiving EVs on the market when it comes to battery health.

 

We had some concrete work done, and also installed a subpanel in the garage. Between the two activities, and the way the tax code reads, we should be getting back the full $1,333.33 in rebate from our ~$4000.00 work done.

Pretty awesome there are benefits to improving your land you own.

our accountant said it should not change for 2022, but typically these benefits slowly decrease.

 

You may need to see if you can support the load of a Level 2 charger on your main breaker panel first. If you have electric heating and other electric appliances, you either will have to upgrade to a 200A panel or probably put in a load manager to trip or de-energize on the EVSE circuit.

If you plan on getting a second EV down the road then it might be worthwhile.

 

I'll put in my green-mania-input here... While cost is a significant factor in most drivers, I was purely driven to go to the SE by guilt. I drive 25 miles per day for work, and while I love my current DD I actually lost the joy knowing what I was doing. Thrilled to find the new SE as an option I'm awaiting its arrival next month, but I'm also in Cali, and have solar for our house, with a PowerWall to help with after hours E. When I test-drove a base SE last month, I fell in love, and realized I couldn't justify my current DD. I realize that the grid, and possibly many states are behind the drive for EVs, but felt the need to get myself into a mindset beyond myself! Can't wait for my new car, and I'm pretty sure I won't miss what I'm putting into the atmosphere!

 

I'm curious to see how NEM 3.0 will turn out for those in California. If it passes I guess off-grid will be the way to go for solar!

 

This is exactly why I got mine. I’m sick of the air quality alerts Colorado gets every summer. We should be able to see the mountains clearly every day. The Mini probably won’t offset a single one of the countless coal rollers we have, but each of us can only do so much.

 

On a cold morning when you can see the vapor coming out of all the exhaust around you and you realize your car doesn’t do that it really makes you think…

 

Agreed, I can only do my part, in the hopes it makes a difference. And this awesome little SE is worth the change IMHO!!

 

50 MPG sounds great in theory, but those average figures, especially in the winter, are far from 50. A 20-25% hit isn't unheard of, we saw such a hit with the Malibu below 20F. If such a vehicle is a hybrid, expect a slightly larger hit with hybrid battery inefficiency. And an overall larger hit if one has a habit of pre-warming at idle before setting off.

Winters are tough on transportation.



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I compare my new SE to our RAV4 Hybrid, which is already a pretty efficient vehicle for its size. In the warm months, it gets 39 or 40 MPG for us and down in the low 30s in cold months. Even at the high side, it costs us about 2x per mile what the Mini does.

Rob