by tzs | 2025-12-28 03:46:52+00:00
If your vehicle has V2H (Vehicle to Home) the way it generally works in newer cars is that you have a bidirectional charger that can be used to connect the car battery to an external inverter, which is then tied into your house grid the same way a generator would be, e.g., via a transfer switch on the circuit you want to power.

This isn't cheap--I think it was generally many thousands of dollars for the cars I looked at that had V2H when I was EV shopping--but it generally gives you something something in the 9-20 kW range of power. For most people that gets into the territory of "as long as you remember not to use the electric clothes dryer at the same time you are making a meal that uses the electric oven and all of its burners you can just continue as if power is not out".

I seriously considered it. In the summer I use around 8-10 kWh per day, and in most of winter under 40 kWh per day. With a car with an 85 kWh battery, keeping it in the 20-80% range, and keeping it near 80% when outages are likely, That would give me several days of backup power during a summer outage, and over a day during a winter outage. In 18 years in my current house I think I've only had one outage that went over a day, and never had an outage so widespread that I would not have been able to find a public DC charging station within 10 miles to recharge the car if an outage actually did last long enough to take it down to 20%.

But the cars with V2H were out of my price range, even before adding the cost of the equipment to use V2H.

If your vehicle has V2L (which is what the one I bought has) it is considerably cheaper. The car gives you one or two outlets similar to ordinary household outlets. Mine gives a single outlet, which you get by plugging an adapter into the charge port. With these you generally don't try to tie it into your house grid. You just run an extension cord (or two if your V2L provides two outlets) to where you want power.

Some people get some sort of socket installed on the outside of their house that a cable from the car's outlet can be connected to, with that socket connected to an indoor outlet. Me, I just leave sliding door open enough for an extension cord to go through, and then stuff the gap with some foam strips that I got at Home Depot.

It is surprising how much a single 120V 15A circuit can do. What I need to get through a one day power outage comfortably (which as mentioned would be an unusually long outage here) is: (1) power for the fridge, (2) power for an electric space heater, (3) power for my computer area and cable gateway (if cable is not out), (4) maybe power for some cooking, and (5) water to flush the toilet.

Any time the weather forecast even hints at something that could cause widespread outages I fill a bathtub with water for #5. For the rest I've been monitoring power used for those things with a bunch of energy monitoring smart outlets (Tapo P110M controlled by Home Assistant using Matter).

For #1, my fridge during a normal cycles draws 90-100W. During a defrost cycles it draws 400W. I have wireless thermometers in the fridge and freezer compartments so I can easily coordinate with other uses such as cooking to make sure I cook at a time when the fridge is going to not need to run for a while (which I can ensure by unplugging it).

For #2 my space heater is usually 1500W, but I've got another one that is supposed to be 1500W but due to age is only 1300W, and I've got year another one which is 1500W on high but has a medium setting that is 1000W. On all but the coldest days 1300W and probably 1000W would keep it warm enough as long as I'm warmly dressed.

For #3 my entire computer setup (Mac Studio, 27" 5K monitor, 24" 1920x1200 monitor, speakers, external Thunderbolt drive bay with 4 SSDs), a network switch, and a Hue hub is about 130W with short spikes to around 170W. If I turn off the second monitor that drops about 25W from that. The cable gateway is 15W.

For #4 I've got a microwave, a toaster oven, and a couple George Foreman grills. The microwave draws over 1900W for the first minute or so on high, but I can set it lower and it is an inverter microwave so on lower settings it actually reduces the amps drawn rather than just cycling between full and off. The toaster oven is 1000W and the biggest GF grill is 1200W.

I should be able to run all of these, as long as I take some care to not run too many at once. Some observations:

1. If I'm not going to use the computer for a while, such as when sleeping, I can run the 1500W space heater, turning it off when the fridge needs to run. I could actually then turn it back on once the fridge has started and gotten past its inrush current (20A, which my V2L has no trouble with). It would then be 1600W total unless the fridge is doing a defrost cycle than it would be 1900W. That's fine because the 400W defrost phase only lasts about 10 minutes and the non-defrost cycle only a bit over an hour, and it is around 3 to 8 hours (depending on how often I open the fridge I assume) after a cycle ends that it needs to run again. That counts as an intermittent load and so should be OK with my extension cords (rated 15A intermittent, 12A continuous).

2. If I'm using the computer I can switch to the 1300W space heater. That plus the computer both in continuous used would be under the 12A continuous rating of my extension cord. When the fridge needs to run I'd have to switch to a lower setting on the space heater until the fridge is done.

3. When I need to cook I'd just need to time it so it happens when the fridge won't need to run, and turn off the space heater while cooking. Nothing I'd be cooking in the toaster over or the GF grill takes more than 20 minutes. The computer stuff could remain powered during this.

4. If I don't have a bathtub full of toilet flushing water, I might be able to run my well pump from V2L. It's 120V with a 1/2 HP motor which would be under 1000W, but the inrush current may be too high. The specs say maximum of 44A, but from what I've read many people have had success with motors with that kind of inrush current, and the way the V2L system works it is safe to try it--worst case is the V2L safety systems shut it down. I just haven't gotten around to trying it yet.

Overall then it seems like that single 120V 15A from V2L will actually be enough to get me comfortably through most power outages. I had not expected that when I got the car.