Forget 'Baby on board'

[Ron Selzer]

I really don't know for certain, but I'd be wary equating a transfer switch for a generator with the requirements for a solar source that is feeding power all the time. If the solar connected only when the power failed then it would be acting like a generator installation but I don't believe that is how it is done.

Alan stated that the solar disconnects when Utility Co. power is lost. Also he has several disconnects already. Now it would be possible to install an Automatic Transfer switch OR a manual transfer switch to totally disconnect off of the incoming Power Lines and use the Cybertruck to power the house. OR might only need some more control circuitry.
DEFINITLY WOULD NEED LOOKED AT CLOSELY TO MEET LOCAL RULES.
Somebody would have to get up close and personal with what is there and design what is needed. Probably lots more money, however only Alan can say how much it is worth to him.
Ron

[Brian Elfert]

Most grid tie solar inverters need a source of power to sync to. Even if you had a transfer switch to isolate your solar the panels won't produce any power. This is starting to change. The latest Enphase microinverters can produce power even if the grid is down.

[Jim Koepke]

Does anyone actually think this all hasn't already been worked out by the power companies? When my neighbor installed solar panels the power company installed equipment so they could provide power to the grid.

The only real problem would be if someone is trying to instal solar and connecting to the grid without the power company knowing. Those are likely the ones who end up with a pile of ashes where their home once was.

jtk

[Alan Lightstone]

Does anyone actually think this all hasn't already been worked out by the power companies? When my neighbor installed solar panels the power company installed equipment so they could provide power to the grid.

The only real problem would be if someone is trying to instal solar and connecting to the grid without the power company knowing. Those are likely the ones who end up with a pile of ashes where their home once was.

jtk

Jim:

I think you are misunderstanding the issue. I provide a nice surplus to Duke Energy, for which they pay me <1/4 what I would pay them. On virtually every sunny day I send power to the grid.

It's when the grid goes down, and I want to have my large solar array provide my house with power that it is blocked.

Ultimately, some form of battery backup will be necessary. Tesla will have their Cybertrucks able to provide power to a house. Not available yet. But when it is, that's my battery backup. My question, which no one at Tesla can/will answer is whether or not my solar array can recharge the Cybertruck batteries when the grid is down.

[Bill Howatt]

If your solar array can provide the Kw capacity I don't see why it can't charge the battery assuming somewhere in your equipment is an accessible inverter outlet that converts the solar DC into 240V, 60Hz AC.
If the power (Kw) available from either array size of poor sunlight is low then isn't it just an issue of taking longer? But I can't say if Tesla puts any quirks into a generic situation.

[Alan Lightstone]

If your solar array can provide the Kw capacity I don't see why it can't charge the battery assuming somewhere in your equipment is an accessible inverter outlet that converts the solar DC into 240V, 60Hz AC.
If the power (Kw) available from either array size of poor sunlight is low then isn't it just an issue of taking longer? But I can't say if Tesla puts any quirks into a generic situation.

Oh no doubt it would be physically capable of charging the car batteries. The question is whether or not their system (it will be proprietary) will allow it. Especially as Tesla Solar did not install my solar array and it is not their inverters. There are devices that they say will be necessary to install to use the car to power the house.

Tesla calls it Powershare Home Backup and there is something about a Gateway V3 adapter/device. That's really about all the information that they say on the Cybertruck order website.

[Bill George]

It would be possible to install an another Inverter in parallel to to the existing just to feed a 240 circuit that only feeds the Tesla charging station, not connected to the grid. I could do it to mine if needed.

[Jim Becker]

Alan, how would a traditional fossil fuel generator be handled in this situation where you have solar as you describe with the draconian prohibition of using it during a utility power outage? In essence, a battery "generator" is what would fit in that same space.

[Alan Lightstone]

Alan, how would a traditional fossil fuel generator be handled in this situation where you have solar as you describe with the draconian prohibition of using it during a utility power outage? In essence, a battery "generator" is what would fit in that same space.

A propane generator (we have a tank here, but no natural gas available) would be able to power the house during a grid blackout (automatic or manual transfer switch). The solar panels, I believe, would again not be usable during the time the grid is out.

If at all usable, I would think they would have to supplement the generator output, otherwise that brownout scenario would occur. Not sure how equipment would handle that scenario. Certainly not technologically impossible, but I don't think fossil fuel generator companies (Generac, etc...) would have any interest in that.

[Jim Becker]

A propane generator (we have a tank here, but no natural gas available) would be able to power the house during a grid blackout (automatic or manual transfer switch). The solar panels, I believe, would again not be usable during the time the grid is out.

If at all usable, I would think they would have to supplement the generator output, otherwise that brownout scenario would occur. Not sure how equipment would handle that scenario. Certainly not technologically impossible, but I don't think fossil fuel generator companies (Generac, etc...) would have any interest in that.

Generac actually has an excellent battery backup solution...I considered it for here (along with solar panels), but in the end, I decided we would not be at this property for long enough to make it worth the investment, at least for us. They use the same automated transfer switch as with the gas powered generators (which I did opt for, having an all electric house other than oil backup on the heat pump) so that potentially would be a solution you could use. During normal times, the solar panels could keep the battery array topped off and if the utility goes down and they shut off your panels, you still have power. It's just coming from a bunch of very heavy batteries rather than from a traditional generator.

[Alan Lightstone]

Generac actually has an excellent battery backup solution...I considered it for here (along with solar panels), but in the end, I decided we would not be at this property for long enough to make it worth the investment, at least for us. They use the same automated transfer switch as with the gas powered generators (which I did opt for, having an all electric house other than oil backup on the heat pump) so that potentially would be a solution you could use. During normal times, the solar panels could keep the battery array topped off and if the utility goes down and they shut off your panels, you still have power. It's just coming from a bunch of very heavy batteries rather than from a traditional generator.

I extensively looking into getting Tesla Powerwalls a few years ago. Also looked at a few competitive products. I also look at them periodically.

To power our whole house would take 4 Powerwalls, which would run $46K. Now one thing you realize (or should realize) living in hurricane country is that you don't have to power your whole house if the grid goes down. You need 1 room with AC (hurricanes in summer the issue down here), some lights, and fridge/freezer. Really don't need to power the whole house. So I actually had my electrician reorganize my circuit breakers to have those loads on one panel, to make that easier. Planned on having 1 floor of the house have power in an emergency.

I also had an energy monitoring system installed on those breakers, to see just how much power they use during the day. Easy-peasy. Knew what I needed. Time to get the battery backup system.

At that point, for whatever reason that cost them a sale, my solar installers dropped the ball and didn't return my calls about getting the battery backup installed. A year later, the company called and asked if I had any interest in buying a battery backup. I told them too late, they lost the sale.

After looking into the economics of getting battery backup, it doesn't make any financial sense with my utility. Duke Energy only pays me back $.025/Kwh of electricity I send back to them as surplus, and now charges $15.6/kWh for usage. So if I used the batteries every night to power the house, and charged them with the solar panels every sunny day, it looks like the batteries will pay for themselves in about 15 years. But their lifetime is about 10 years. I've had a few solar companies confirm this. The honest ones here will tell you that they will never pay for themselves. A whole-house propane generator here would only cost around $15K.

Since I built the big homemade UPS for our medication fridge, the real risk (other than inconvenience) of a prolonged power outage here is just food in the fridge. Economically a drop in the bucket compared to the cost of a battery backup system. Now on the other hand, if a huge battery in an EV like the Cybertruck can provide that power, the economics change. And if every 3 days you need to run to the Supercharger for an hour to recharge the Cybertruck, not a big deal (during the last hurricane here the vast majority of the gas stations had no power. I checked 5 Superchargers - all were working fine.)

Now if I lived in a wildfire prone area, like some in California, that often have brownouts or blackouts, I'd likely give a different answer. Or if my utility paid me the same for surplus that they charge for usage.

[Jim Becker]

I extensively looking into getting Tesla Powerwalls a few years ago. Also looked at a few competitive products. I also look at them periodically.

Tesla eventually "closed" their offer and started requiring their own solar roof or panels, if I'm not mistaken, in order to buy the PowerWall system. Originally, it was able to be used with other solar collectors, again, AFAIK, but I could be wrong about this. When I priced the Generac system, I found it pretty reasonable for the backup scenario I wanted which was on the upper end of things, although it was more than I could justify for how long we will live here as I previously noted. The good news is that solar solutions, including battery backups, are continually coming down in cost and there are a lot more options available on the market.

[Steve Demuth]

After looking into the economics of getting battery backup, it doesn't make any financial sense with my utility. Duke Energy only pays me back $.025/Kwh of electricity I send back to them as surplus, and now charges $15.6/kWh for usage. So if I used the batteries every night to power the house, and charged them with the solar panels every sunny day, it looks like the batteries will pay for themselves in about 15 years. But their lifetime is about 10 years. I've had a few solar companies confirm this. The honest ones here will tell you that they will never pay for themselves. A whole-house propane generator here would only cost around $15K.

You might look again. The price on batteries has dropped dramatically in the last 3 years. What would have cost you $46K 3 years ago can probably be had for closer to $20K today.

Also, doesn't the price differential between what you export, and what you consume from Duke make batteries more attractive, not less? If you can charge enough battery capacity most days to power your house during the 18 or so hours the panels aren't producing at scale, that's saving you the difference between the rates, minus efficiency losses in going to and from the battery, for each kwh the batteries provide. That's be in the vicinity of $0.10 per kwh in your case. Still not going to pay for itself in a short period, but at less that $8000 for a 13.5 kwh Powerwall 3, it'd be in the vicinity of paying for itself over the lifetime of the battery, and you get the backup as a bonus.

[mike stenson]

Most grid tie solar inverters need a source of power to sync to. Even if you had a transfer switch to isolate your solar the panels won't produce any power. This is starting to change. The latest Enphase microinverters can produce power even if the grid is down.

Those must be newer than a year.

[Steve Demuth]

Those must be newer than a year.

They've been available since 2021 from Enphase. If you have IQ8 inverters, those are grid-forming capable. Whether or not, and when, they will provide AC power absent grid input depends on how they're configured (which of course depends on what your utility will permit).