Advice needed for Tesla Rooftop Solar - TIA!

[MelaniainLA]

I'm in the Los Angeles area on Southern California Edison and have a question about getting Tesla Solar and whether it's worth it.

We currently have 3 Tesla Powerwalls (which were free referral prizes) but NO solar. We use them to store cheap off-peak power (we are on time of use TOU-D-PRIME plan with SCE) and power the house only from Powerwalls (off grid) during peak times 4-9pm daily. So, with round the clock off-peak power and a very efficient home, our power bills are relatively low, but steadily climbing with SCE's rates going higher every year.

Given the weird configuration of our house (electrical panel is in detached garage in backyard, requiring possibly expensive trenching to get solar on the main house, which has limited space for solar to begin with because of skylights etc), we can fit about 10 panels (their minimum size) on the roof of the detached garage (which is where main panel and Powerwalls are located). These panels would produce a meaningful chunk (~50%) of our needs.

-Wondering whether you think it's worth it to do this. What do you all think?
-Currently, we fill up the 3 Powerwalls (we only use power from <1 of them at MOST given our low amount of power usage in the peak periods) from the grid using off peak power. Would SCE allow us to "top off" our Powerwalls from the grid if the solar production from this limited system is insufficient to recharge the Powerwalls?
-Tesla's estimated power production from these panels seems low, as in assuming 3 hours of full production per day averaged year-round. How accurate are their estimates, and how often do you see significantly higher production?
-They just switched from 425 watt panels to 405 watt panels -- is there any difference in quality between these panels?
-Do they ever offer discount for already having Powerwalls in place, because they could more easily wire the system perhaps?
-Any other questions I should be asking?

THANK YOU!

 

[jjrandorin]

Wondering whether you think it's worth it to do this. What do you all think?

No, because you would be on NEM 3.0 by adding solar now. If you were going to do this, the time to do it would have been when you could still be on NEM 2.0 (before roughly april of this year). Now, I would wait to see if NEM 3.0 is tweaked.

 

[MelaniainLA]

No, because you would be on NEM 3.0 by adding solar now. If you were going to do this, the time to do it would have been when you could still be on NEM 2.0 (before roughly april of this year). Now, I would wait to see if NEM 3.0 is tweaked.

What massive JERKS for screwing up solar with the NEM 3.0. That said, I have 3 Powerwalls and would be getting fewer panels so I shouldn't be sending any power back to the grid.. this still apply here?

 

[jjrandorin]

What massive JERKS for screwing up solar with the NEM 3.0. That said, I have 3 Powerwalls and would be getting fewer panels so I shouldn't be sending any power back to the grid.. this still apply here?

Yes, it still applies, because adding any solar will trigger your current plan to be changed to NEM 3

 

[Marktm250]

Having 7 years experience in South East TX with two solar systems, the overall average has been 3.3 hours full rated panel production/per day. I'd guess LA would be somewhat better as we get many more rainy days. 3 does seem low.

Not having any knowledge of your electricity plan, it would seem that having spent the $$s on energy storage already would drive the economics of solar (with incentives) favorably. I've paid off both my solar installs in the 7 years with a fixed plan of around 11 cents consumption and 6.5 cents/kWh production (grid).
For me, the ability to go off-grid and live on solar/batteries when needed would be very attractive especially if the economics are even close. Of course, we have hurricanes fairly regularly.

 

[jjrandorin]

Not having any knowledge of your electricity plan, it would seem that having spent the $$s on energy storage already would drive the economics of solar (with incentives) favorably

This OP didnt spend any money on Powerwalls / Energy storage. They were free referral rewards.

NEM 3.0 means solar in CA is a lot less favorable than previously.

 

[Marktm250]

The fact that he has the Powerwalls might help his economic analysis. In Texas, we have what is called the EFL - Electricity Facts Label - a standard disclosure of costs that allows detailed comparison. There are so many plans available in my area, especially for solar producers and EV owners. Tesla has a really good plan if you drive an EV many miles during the day and can charge quickly at night ($25/month total). I'm hoping that Tesla will open up bidirectionality in their vehicles. When they do, I'll likely put in solar, a single PW and the fastest charge system available. Many days I could power my house within this $25/month cap! (maybe, as most likely the PUC will change the regs to discourage home "microgrids"). Is something similar happening in CA with NEM 3.0?

 

[jjrandorin]

The fact that he has the Powerwalls might help his economic analysis. In Texas, we have what is called the EFL - Electricity Facts Label - a standard disclosure of costs that allows detailed comparison. There are so many plans available in my area, especially for solar producers and EV owners. Tesla has a really good plan if you drive an EV many miles during the day and can charge quickly at night ($25/month total). I'm hoping that Tesla will open up bidirectionality in their vehicles. When they do, I'll likely put in solar, a single PW and the fastest charge system available. Many days I could power my house within this $25/month cap! (maybe, as most likely the PUC will change the regs to discourage home "microgrids"). Is something similar happening in CA with NEM 3.0?

None of this is applicable to someone in CA, where the OP is, though.

 

[jjrandorin]

The fact that he has the Powerwalls might help his economic analysis. In Texas, we have what is called the EFL - Electricity Facts Label - a standard disclosure of costs that allows detailed comparison. There are so many plans available in my area, especially for solar producers and EV owners. Tesla has a really good plan if you drive an EV many miles during the day and can charge quickly at night ($25/month total). I'm hoping that Tesla will open up bidirectionality in their vehicles. When they do, I'll likely put in solar, a single PW and the fastest charge system available. Many days I could power my house within this $25/month cap! (maybe, as most likely the PUC will change the regs to discourage home "microgrids"). Is something similar happening in CA with NEM 3.0?

None of this is applicable to someone in CA, though.

Many days I could power my house within this $25/month cap! (maybe, as most likely the PUC will change the regs to discourage home "microgrids"). Is something similar happening in CA with NEM 3.0?

Its the opposite actually. CA is discouraging having solar only, and encouraging someone to have enough battery storage paired with their solar that they dont really need to export (net meter) at all. They are doing this by de valuing the price they pay for exported solar so much that it doesnt make sense to export it. In effect, they are encouraging everyone to be as self reliant as possible, if they choose to get solar at all.

 

[wwu123]

I'm not sure why NEM3, or any NEM, really matters here, if the OP already has 3 Powerwalls, and uses less than 1 Powerwall worth (13.5 kwh) during 4-9pm peak periods. Even without more details, with the advantage of 3 Powerwalls, it suggests they would never have to export, nor have to import except during super off-peak.

So it seems worth penciling out the payback period, the value of the solar is basically the annual production times super off-peak rates. I think the OP is saying by "3 hours of full sun production" that a 4.05 kw array is estimated to produce (4.05 * 3 * 365) = 4434 kwh. That is somewhat low, suggesting some shading or sub-optimal orientation. But I have a 4 kw array that only generates 5000 kwh/year due to shading - and it paid back after 6 years even paying much higher $4/watt rates years ago.

4434* $0.26 = $1150/yr in value. (I didn't use TOU-D-PRIME as there's additional base charges of about $12/month, not sure that would still be the best plan.) If the net solar cost is about $2/watt after fed incentives, that's $8100, and a payback period of about 7 years. Some feel that's too long; to me that's reasonable if one plans to stay in the house for 20+ years. The solar will probably be productive for that long, and can generate 3X ROI over 20+ years, which is significant. But this assumes the Powerwalls continue to function too - currently at less than 33% duty cycle, they won't die from degradation, but could fail by other means.

Given the expected rise in electricity rates, it would probably be an actual payback period of 4-5 years - I would definitely consider it. And if there's no shading situation, the actual kw production would be higher, further reducing the payback period.

EDIT: OK, one small but important caveat, OP suggests 4400 kwh is half their annual consumption, so they would be net importers During summer though, the panels could generate more than daily consumption, resulting in some export with poor compensation, and then more import in winter at retail rates. That could blunt the benefit somewhat. More details would be needed to evaluate if this is an impact on ROI, and whether it's significant....