Using your Electric Vehicle to power your home

Q-Dog said:

I have been thinking about this lately and have some thoughts.

How about a house battery backup with enough battery to cover overnight loads plus average daily EV use. Add enough solar to recharge the house battery on an average day. Now you can charge the EV from the house battery over night, charge the house battery from solar during the day, and still have enough battery capacity to cover an overnight outage. In a long power outage the EV can top up the battery if needed.

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Only challenge here is $.

My EV, for example, has about 100 KWH battery.

I commute about 90 miles per day, round it out to about 30 KWH.

So for a typical day, I'd need a full rack of LifePower 4 to charge the EV overnight, and enough panels to charge that back during a normal day, so call it 8 KW of panels. Not crazy, but you are probably at $10-12K for this solution, above and beyond normal house loads, blah blah blah.

Now that I write this out..........where is my credit card again?

houseofancients said:

a selling point with a very very limited use case ( IMHO at least)

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True. I have plenty of neighbors that have no backup for power outages. So this is a feature they wouldn't need. Oh, wait!

Cars have ALWAYS been backup power solutions through their 12v systems but they're usually limited to under 1kw, more like 600w continuous at idle, and you have to leave the giant engine running to power your silly inefficient 600w system. But it's always been better than nothing.

EVs and Hybrids have pushed that up to an entirely different level of power AND practicality because IF you are bold enough to tap into the high voltage side you can simply feed it to the mppt of a house inverter you may already have, and have either A. A giant battery (EV) or B. The best generator in the world that is super quiet, has a huge fuel tank, and TURNS ITSELF ON AND OFF AS NEEDED (Hybrid/PHEV). Lots of caveats there but the upsides are attractive enough that some people will go to the effort to do it.

It is absolutely my intention to completely replace all the generators ive had so far, with my old 2001 Honda Insight (hybrid), although it's a big project in its own right. But it has enough upside to be worth it, imo.

I think the thing that will make using vehicles as backup power practical for more people is actually that they're coming with bigger 120vac inverters which will simplify the 'power transfer' to the home system. Lots of cars come with dinky 120-400w inverters already, but some such as the Lightning and Powerboost are capable of powering an entire house and that capability will slowly proliferate as knowledge of the possibilities spreads. Like probably most of us here remember how that one guy powering his house from his old Prius hit news all over the country when the east coast lost power for like 2 weeks, but i dont think the average person remembers that or sees this as a possibility. As the awareness increases so will the demand.

If you have TOU rate plans then V2H for peak shaving/off-load could make sense since peak hours (at least in California) are usually around 4-9pm.

EV battery to power house during power outage is a point, but to me the most important point is elsewhere.
If you pay, let say, 0.40$ / kWh during peak consumption 4-9h pm period and 0.05$ / kWh during night, it can make a lot of sense to power your house from your EV at 4-9h pm and charge after during night.

It's almost that here in Québec as Hydro Quebec pay me 0.50$ / kWh I don't consume during peak period event (usually 4-8h PM when it really cold outside).
After 8h pm I can charge my EV at 0.06$ /kWh.
The things is those event only happen around 10 days / years while I would expect this to happen every day.

Here some DIY electric vehicle to power your home (via MPPT).

houseofancients said:

and my points are :

if you want to make it work like a proper 24/7 battery, the vehicle needs to stay on site
if you want "free" charging the vehicle needs to be on-site
if you want a backup , the vehicle needs to be on-site and fully charged

maybe works for folks who are willing to accept no power to anything when not home
maybe acceptable for folks always at home

will not work for independent working folks that need that vehicle during the day ( like most of us), unless we accept off site expensive charging ( does anyone really expect "free" power from clients they visit or even employers ?

to me this is a fractional backup at best, but v2h is for most people simply a pipedream

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It's just a backup power source. Just like a generator.
For grid down situations.
It's not a permanent power system. (Proper 24/7 battery)
If there is a blizzard and you are snowed in. And the grid goes down. It's another option to power the necessities.
But, if you have the ability to game the system. It can be used in many ways.

Q-Dog said:

I have been thinking about this lately and have some thoughts.

How about a house battery backup with enough battery to cover overnight loads plus average daily EV use. Add enough solar to recharge the house battery on an average day. Now you can charge the EV from the house battery over night, charge the house battery from solar during the day, and still have enough battery capacity to cover an overnight outage. In a long power outage the EV can top up the battery if needed.

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This is my setup, except for the capacity to charge EV. I only have enough PV and battery for the house.

I have thought about buying more batteries, but think an EV with V2H can be utilized instead. Some EV manufacturers offering free charging for a year or two so this could be an added benefit.

houseofancients said:

Makes for most zero sense.

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For some people it might make a lot of sense.

Let's take my example. Four years ago I had an old Leaf that I drove a short distance to work. At work we had 120V charging outlets we could use (powered by a 440KW solar array on the top of a nearby building.) Plugging in for 8 hours gave me about 12kwhr. Since I used only about 4kwhr getting to and from work, that remaining 8kwhr was free for me.

And if I were living alone (which I wasn't at the time) I would not need backup power at home when I wasn't there. So whenever I was there, power would be available. Of course nowadays with 1-3 people in the house when I'm not there, a dedicated backup battery makes more sense.

I eventually traded in that first gen Leaf for a Prius Prime. The Leaf had a 24kwhr battery pack that had degraded to about 20kwhr. I didn't get much for the trade-in - about $6K. But let's say I lived further away from San Diego (like, say, Ramona or Pine Valley.) First off I'd have more space, and secondly I'd lose power pretty often. At that point I'd be tempted to keep the Leaf and just use it as a stationary battery and an occasional second car.

There are some places in the US where the truck-on-blocks-in-the-back comes standard with most houses. The future may see that truck-on-blocks also powering the house. It's also worth noting that regulatory agencies have not yet figured out how to regulate this. Stationary battery packs generally need UL9540 certification, which is a bear to get. Car batteries do not need such certification. And of course if your EV battery DOES go up in smoke, it's happening outside your house - which is a much better case than having a burning battery inside (or on) your house.

Connection to the grid is an issue. But there are now several Chademo and a few SAE fast chargers on the market, and any such charger will get the car to close its HV contactors and allow access to the battery. There are even a few dedicated bidirectional chargers. And once you have access to that 400V battery, there are a large and growing number of 400V inverters out there that allow easy interface to the grid.

I also commented on that video when I saw it. You have to see it as something that integrates with the system, not something separate. For example, I could use the EV to drive for free in summer - that's a typical use case. However, having the vehicle act as an extension to the home battery would mean I have to use the generator less in winter. My wife or I have to drive to town anyway, or work, and I can buy energy cheap while I'm there (cheaper than typically buying diesel, or even the effort for making my own biodiesel for the generator) and put it into the home battery at night. Since I only use 5kWh per day or so to run the house, I would only have to siphon a little from the car to eliminate a lot of generator use. It complements the system quite nicely, especially with an efficient EV and relatively short commutes.

I'm just waiting for the EV I want: small and efficient, LFP battery. heatpump and V2L for a reasonable price. The BYD Dolphin comes really close...

I actually had a whole thread about this:


With the first F150 Lightning hitting the used market - and soon being available for the $4000 used car EV credit - it gets a strong idea to use those trucks a battery first and as truck second.

Around here the Pro Lighting sales around 42k - they are sitting forever on the lots - so I guess out the door should be around that price. Minus 4000 used EV point of sales credit - so we are looking at $38k for 98kWh of battery.

That is getting close to par with Server-rack batteries. And you get a free truck

I only see the EV as a backup to the existing backup system.
Only for very difficult times when travel would also be avoided and basically homebound and desperate.

Who will be the first to claim the 30% federal credit for home battery use of the vehicle.....

time2roll said:

Who will be the first to claim the 30% federal credit for home battery use of the vehicle.....

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I like your thinking, I was able to claim the 30% tax credit for the batteries and Panels on my RV.


Just need to add a few panels to the Lightning bed and then somehow got itemized recipe from the Dealer which shows the battery as it's own part

houseofancients said:

a selling point with a very very limited use case ( IMHO at least)

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welcome to the Holland 99.9% up time can`t remember when i had the last power outage

our set up is solar+battery+EV, because we can go upward of 10 days without sun in the winter months. Since the household is 99% electric now (wife still insists having a flame); the EV's big pack keeps the mini-splits/HPwater heater going during extended outage; and can be driven off to "refuel"

I follow these folks and I'm wondering.... is the vehicle inverter (system, wiring, heat) rated for continuous use the way a Victron inverter is - e.g. the inverter is not likely core to the drive train but an accessory. My AIMS inverter died at 5 yrs / 25,000hrs of operation and needed capacitors replaced on the control board. The vid is during winter (cold) and I wonder about summer, 100F temps etc. They had that mysterious shut-off mid experiment that was not yet explained.

I'm guessing the EV auto makers aren't thinking 'continuous, day after day use' yet, but maybe as things mature.

eXodus said:

Minus 4000 used EV point of sales credit - so we are looking at $38k for 98kWh of battery.

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Vehicle must be 2 model years older than current year when you take the credit, so 2022 model year and older.

Used Vehicle credit only applies to sale price below 25K.
If you are trading in a vehicle, they can drop your trade in price and the sale price, but I'm sure there's a limit to how far you can take that.
might be some sales tax implications.
I was able to get the credit this way on a vehicle that was listed for 27-ish

If it's just a 2023 thats still sitting on the lot from new, it should still qualify for the $7500 new credit.

OffGridInTheCity said:

I follow these folks and I'm wondering.... is the vehicle inverter (system, wiring, heat) rated for continuous use the way a Victron inverter is - e.g. the inverter is not likely core to the drive train but an accessory. My AIMS inverter died at 5 yrs / 25,000hrs of operation and needed capacitors replaced on the control board. The vid is during winter (cold) and I wonder about summer, 100F temps etc. They had that mysterious shut-off mid experiment that was not yet explained.

I'm guessing the EV auto makers aren't thinking 'continuous, day after day use' yet, but maybe as things mature.

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Rated for continuous duty. And covered under the 8 year warranty.

lexio said:

welcome to the Holland 99.9% up time can`t remember when i had the last power outage

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Well had a few, but indeed very dew and far between, so purely as a backup it makes -0- sense here...

What does make sense is playing the dynamic price game here, and avoid taxes as much as one can

lexio said:

welcome to the Holland 99.9% up time can`t remember when i had the last power outage

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houseofancients said:

Well had a few, but indeed very dew and far between, so purely as a backup it makes -0- sense here...

What does make sense is playing the dynamic price game here, and avoid taxes as much as one can

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you should visit North America, it's like going back in time, the people there still string powerlines on wooden poles, like Europe did in the early 1900s. https://www.cnbc.com/2023/02/17/why-americas-outdated-energy-grid-is-a-climate-problem.html

My UPS in my house in Florida has multiple outages - per month. The one in Germany gets maybe 1-2 a year.

That's my use case as well.

My wife commutes 250km/day. 2 tanks/wk @$100/tank in the family car, 4 tanks in the truck. I couldn't use the EV daily in dark winter as a car(unless is was actually sunny) but I could use it as a bigger battery in winter when I need it and for groceries (ie short trips). Charge in town once a week.

Then when the sun returns she can commute in the ev again. We've got enough battery to run for days outside of dark winter.

The gas savings would pay the finance on the ev, so my monthly doesn't change, but I'll burn significant less propane for power generation in dark winter.

upnorthandpersonal said:

I also commented on that video when I saw it. You have to see it as something that integrates with the system, not something separate. For example, I could use the EV to drive for free in summer - that's a typical use case. However, having the vehicle act as an extension to the home battery would mean I have to use the generator less in winter. My wife or I have to drive to town anyway, or work, and I can buy energy cheap while I'm there (cheaper than typically buying diesel, or even the effort for making my own biodiesel for the generator) and put it into the home battery at night. Since I only use 5kWh per day or so to run the house, I would only have to siphon a little from the car to eliminate a lot of generator use. It complements the system quite nicely, especially with an efficient EV and relatively short commutes.

I'm just waiting for the EV I want: small and efficient, LFP battery. heatpump and V2L for a reasonable price. The BYD Dolphin comes really close...

Click to expand...