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Not at $0.55/kWh. Just think about how painful it would be to heat a pool with electricity... We need much cheaper electric power if we want to remove nat gas from the ecosystem.

I don't understand this. If you have a gas boiler, why not have it do all the DHW and bypass the heat pump water heater completely? If it's a modulating burner it's already super efficient, or are you using the heat pump heater just as a storage tank?

In that case, I would definitely use a computer style UPS to protect that system. Given some of the recent stories about PW's not kicking in properly during an outage, I don't think I would depend on them for such a critical task when a UPS can give you much more assurance. I got a large...

The problem is you paid a lot of money for those powerwalls. Based on your configuration, when do you hit breakeven for the cost of the PW's and gateway? Also, SRP prices seem a fraction of what we pay in PGE land. I'm envious!

All panels, though we do have some glass panels on a pergola like structure that allow light to shine through them around the cells so it's not completely shaded below.

I wonder if the vendors at CES would have more info on this. I usually go but skipped again this year because of all the COVID fun. :(

Where do you see this? It's true the Pro doesn't come with the 80 Amp charger, but that can be bought separately. From what I understand the vehicle doesn't come with an inverter for V2G, it routes DC out through the 80 amp charger to the Sunrun inverter. So there should not be a difference...

Well, I think solar battery storage is in the news, and even the PUC is talking it up in the NEM 3.0 discussion. Tesla is the leader in battery storage by far, so people must think it makes sense somehow, but the math isn't that complicated. I am a techie, and would love to install...

This is a key thing for folks to understand. batteries are not a viable substitute for a generator. And if you buy a generator and have the backup functionality paid for, then acquiring powerwalls just for peak demand load shifting doesn't make any financial sense, even in PG&E land's...

The new Ford Lightnings would seem to be ideal for this, though prices keep going up. However the base config is 98 kWh, and the extended range is 131 kWh! The latter is like 10 powerwalls. Obviously, you don't get 70 kW inverter output, but for backup or load shifting, you don't need that...

Indeed. This is why Powerwalls are not really an alternative to a generator. They might be able to help (if they acted like the enphase system you outlined), but they are not a substitute, as this weather is showing everyone. I'm not sure why people ever thought they would be. Massive is...

The cheaper home "backup" NG generators really aren't designed for this kind of use anyway. You'd end up having to service them fairly often, and maybe it would not be there for an outage when they were really needed. The industrial units are a whole different animal though. We got a 30KW...

I wanted to go do a whole-house powerwall installation at our new home, and had a 400A feed as well. Because of the issues with having to do split feeds it ended up being too complicated. I would up going with a generator backup instead. We did wire in a bunch of cabling for a future...

It's hard to make the economics for Powerwalls work, even with usurious PG&E rates here in NorCal. And for backup power, it's hard to beat a generator for whole house backup. Obviously if you have a blackout and it's been smoky and you don't have much power stored, it's an issue. But it's...

PS The key point the video makes is that you can use historical data on ACTUAL load, so that can be used to size the generator adequately. You can get that from the electric utility, so that probably is pretty easy to do. For a large genset like mine, that works fine, but I don't know how many...

Mike Holt has an excellent video on this topic that can be found here: I have found his stuff really helps in understanding the NEC and what the NEC was trying to accoplish in a particular part of the code.

My genset has an overcurrent shutdown feature, as I am sure the GW does as well. Maybe that qualifies under "load management"? This issue never came up with my AHJ, only that the ATS had to have the full rating of the service.

Wow, I don't think any residential genset install is consistent with that. And why wouldn't it apply to powerwalls as well?

The ATS is 400A just like the service feed. That's code too, and pretty easy to deal with.

Just to my point about making it easy to use a 3rd party ATS, Generac builds exactly that for it's Powerwall equivalent system: https://www.generac.com/GeneracCorporate/media/Library/content/Clean%20Energy/PWRCell_ATS_SpecSheet.pdf It's really just a software driven control interface. I...

Not sure what "a lot" of power is. Before the solar was switched on, we were burning about 90 KWh on a hot day in the peak of summer with HVAC etc, pool equipment running max out, and an EV that needs charging every day, etc... That's a lot of energy, but only about 15 amps average load...

Well, I have a backup generator already, so that's not the biggest motivator. If it would work well with the generator, and provide immediate power until the batteries were exhausted etc.., then that's a different animal, but we discussed why this is hard with the 200A limitation the GW's have...

Well, I was trying to look at the best case, which isn't that good. This is a bit puzzling to me, as PGE has some of the highest prices in the US, so I can't understand why powerwalls for load shifting make sense in other cases if they don't work here...

Maybe this doesn't really make sense anyway: Let's do the math here about what can be saved through time shifting. Summer EV-2A rates here in PGE land are approx $0.48 a KWh for peak, and $0.17 a KWh for offpeak. So if I had 4 PWs all dedicated to doing load shifting on a daily basis, that...

Well, I'm not off grid, so that choice doesn't seem to work. I can't put the ATS behind the GW because the GW can't do 400A. And I don't want my wife to have to do manual start of a generator if the power goes out in a storm and I'm away. I guess that's why I keep getting told I can't use...

Thanks for the comments. There is a detached garage where the inverters and all the panels and main transfer switch connect to. The layout is designed to support having a few powerwalls. If the GW2 can deal with a generator ATS being upstream from the unit, then it's an easy install and all...

Thanks for the note. Does the GW2 have more flexibility in terms of using a generator? I don't think the city will let me downsize the main feed to 200A, as it was quite a chore to convince them to let us "settle" for 400A than 600A. My perfect world would be a system where the powerwalls...

Vines, thanks for this info. Perhaps you could give me some insight in terms of whether or not the Gateway 2 could actually enables me to add some powerwalls? My situation is that we have a large new house, accessory unit, and pool (with the usual equipment) and an EV. Everything is super...

Interesting. I'd be interested in getting powerwalls, but I have a 400A feed and backup generator. I could fit the main house feed and one of the HVAC units in a 200A panel, but it would have to be stubbed from the main 400A panel. Because of the backup generator, I assume I can't use it for...

I think you folks are being highly optimistic in trying to use PW's for multiday outages given that many times outages are caused by bad weather that also impacts solar production. Using a generator (gas/propane) is a much more reliable and can handle multiday outages much better than PW's. I...

One of the problems with this approach is that you have to have the gateway managing the grid disconnect. The gateay only supports 200A max feeds, and if you have more than that (we have 400A single phase feed), things get very complicated, esp when the whole house is being backed up. Part of...

Inverter Supply has the BYD 2.56Kwh battery module for sale at $1701, and the base (that supports up to 4 modules) for $747. It's getting close to the Powerwall 2 in economics, but is DC coupled for much more flexibility. They say it works with SMA inverters on the website, but I am guessing...

Can you take photos of the cabling? I'm really curious how all that connects and how they cable it to the inverters. What kind of inverter are you are installing? mike

I think from energy sage that price was for a bigger unit. if it's cost competitive, deals with generators, and has the level of control and integration that the FAQ says, I think they would grab a ton of customers. Assuming they could produce them in volume of course. thx mike

See Smart Home Battery Backup | Energy Storage | Solar Battery | Electriq Power Anyone familar with them? mike

So I am wondering now is this layout is possible with 2 MPAC 1500 controlled transfer switches in an easier way than I was thinking. The Kohler 1500 controller supports 3 source systems, for use with 2 generator systems. The first switch would be configured as the slave switch. When line...

Vines, the normal house power consumption should be relatively modest (all LED lighting, multisplit HVAC, etc..) But the way code requires you to size feeds, combined with the desire to support electric car charging (which normally happens after hours), it's easy to get above 200 Amps, which...

Sorry if I am being stupid here. If we want to make the extra ATS slaved from the Tesla gateway instead of operating around it, there has to be an input to the ATS that commands it to do the transfer instead of it';s own controller deciding based on voltage or current sensing. I can't find the...

I don't think the genset ATS is the issue. If it switches back it's because the grid is there for a few secs, at which point the PW's have either shut down or synced with the grid feed. Are you saying for the 2nd ATS, the one that is in front of the genset ATS. that has to have a delay of some...

Actually, it's not clear to me that this has to be that complicated. We could use a 2nd ATS switch inline with the main service panel, and when the Grid power goes away, it switches to emergency power, which is not connected to anything. The ATS can do this all by itself, it's just...

I think I am understanding what your are suggesting. You take the 15 amp circuit from the service panel, and have the gateway switch that. That generates a 240VAC output to the 2nd 400A ATS. That transfer switch feeds the generator ATS on the normal utility input connection, and then upon the...

Thanks guys for all the info. I have Kohler 400A transfer switch with the MPAC 1500 controller. That controller is very programmable, but it sounds like I'd need a 2nd 400A transfer switch to act as a "prosthesis" for the Gateway? There are cheaper transfer switches from Kohler and others -...

I have a Kohler 400A industrial transfer switch, and it's quite programmable. I don't understand what you are saying about the 120v circuit though. The ATS switches as grid power is lost, isolating the grid feed,. The ATS then starts the genset, but it doesn't have to do that. It will stay...

It may be possible to have the whole house transfer switch flip to emergency power (isolating the grid) but not start the generator unless the powerwall was couldn't handle the load. The ATS provides a generator start signal that could be interrupted. You could do a dual generator setup...

Thanks for the drawing. I don't think we met as I'm from the valley but live in the SF Bay area now... The wiring diagram makes sense but doesn't work for me as I have a 400A feed, and Tesla doesn't support more than 200A. What a PITA the whole gateway product is... Thanks, Mike

shs1, thanks for the note. Can you attach the diagram of how your system is wired? I can have my installer go to Tesla and see if they can support it for me as well. Does your PW or gateway run with a different firmware release than anyone else? You don't describe particularly good support...

Folks, are there any updates on generator support? We're finishing up building a new house, and I'd love to add powerwalls to the solar design, esp. now that the supply seems to be available. However I have a 30 KW generator (it's a big house) for backup power, as well as the associated...

This is interesting - what manual told you about this? It seems it could be a very useful capability, assuming it was actually implemented.

+1 They could even just skip the transfer switch part and use an external transfer switch and provide control signals for genset start and for transfer switch operation. The lack of a 400A gateway is preventing me from buying 4 powerwalls. I guess they can't even produce enough for their...

What are these guys thinking? Maybe they don't ever intend to release this model in the US? But seems an odd design - do they really save a lot of money by lowering the current rating on the relays? The design seems pointless.