A fundamental problem here is that V2H during an outage requires a disconnection device (in the NEC this is a “microgrid interconnect device”), and the manufacturers of such things have made no effort whatsoever to standardize the control protocol. This means that you cannot build an islanded-V2H-ready house and just plug in a car. So the whole concept is kind of dead in the water.

At least Tesla is vertically integrated enough to pull it off within their own product portfolio, but this has approximately no value if you want to use a non-Tesla car.

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boulos a day ago | parent | next [-]

You can't do just V2H, but Enphase and others have moved to simpler meter collars and grid disconnect for exactly this reason.

The main question for this thread remains who the Enphase / ISO standards friendly OEMs will be. With Tesla saying they'll allow it now, maybe others will get onboard, but the risk is that they wall themselves off.

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amluto a day ago | parent [-]

What Enphase/ISO standard is this? I’ve never heard of it, and my attempt to search came up with nothing useful. There’s ISO 15518-20 bidirectional, which seems like it barely solves the problem.

It should be possible for a vehicle’s built-in inverter/charger, the EVSE, and the MID to all cooperate even if all three are from different vendors, but this is not a thing.

	▲	hedora 17 hours ago \| parent [-]
		I think the standard is called "V2H". It's unobtanium from what I can tell. If you have a Ford EV and a SunRun house, then it supposedly has worked for a few years now. (But that's just vehicle to home charging, not the "V2H" standard.)

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DenisM a day ago | parent | prev [-]

It’s unfortunate and inconvenient. However A transfer switch requires <3 minutes to engage. If a car was able to supply 30-50 amp via compatible plug it would work reasonably well even absent unified v2h standard.

Most recent teslas support 20amp at 120v output via official $100 cable adapter. Some other cars support about 20amps too, eg RivianR2. While it falls short of desirable amperage the car manufactures can bridge the gap if they wanted to. Even now I can run the bare minimum of workloads - a full size fridge, a small AC or Microwave, LED lights, and phone chargers.

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amluto a day ago | parent [-]

A manual switch doesn’t solve the problem: there still needs to be a way to inform the inverter that the switch is open.

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DenisM a day ago | parent [-]

It solves my problem just fine - power critical loads for a few days by spending $100 upfront fir the cable and 5 minutes to manually switch the load. It’s a difference between moving to a hotel for indefinite time and staying put.

Sure you can set a loftier goal and spend tens of thousands of dollars and countless hours solving it. Most people won’t though.

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amluto a day ago | parent [-]

Sorry, what device are you using to supply power once you've flipped the switch? Sure, you can get a (legal, even) manual transfer switch and plug in a little portable generator, but if we're talking about using your car as a power source, this is not going to work.

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DenisM a day ago | parent [-]

I previously used a portable propane generator for a 30amp inlet to transfer switch. In my test runs it didn’t go that high.

Today I could plug in a car that gives off 20amp into the same inlet, it would limit how much load it can carry, but I could stay below 2.4 kw if needed. Why wouldn’t that work?

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amluto a day ago | parent [-]

A lot of houses won’t run off 120V/20A. You’ll also need to kludge around the fact that your house wants 120V/240V.

In any case, serious V2H should support much more than 2kW. An EV with a charger with less than 6kW capacity is almost unheard of. Two EVs should be able to supply twice the current. All that’s technically needed is an charger that is physically capable of operating as an inverter (which I believe adds little cost), some way to derive a neutral (the usual solution is a relay and an autotransformer, again not particularly expensive), and the control logic to convince all of the above to actually operate in this mode.

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leetnewb 13 hours ago | parent [-]

What about using a step up transformer to send 240V to your panel from the 120V output from some EVs?

	▲	amluto 7 hours ago \| parent [-]
		This whole approach has an excellent chance of working extremely poorly. A device intended to power a whole house will have the ability to supply someone’s idea of the inrush current needed by a house, the reactive and harmonic current needed by a house, and the quality of waveform needed by a house. An EV’s 120V socket may be designed to operate one appliance for a while, but a single appliance may be a very different sort of load than hundreds of watts of crappy LED. Also, this whole idea of connecting an EV via a manual transfer switch involves running an entirely separate cable connected to an entirely separate point near your main panel. The cost-effective (but currently mostly impractical solution) is to use the same physical wires for charging and for islanded V2H.