6kW system in Agoura Hills

[gvl]

Got a quote today from another local installer for exactly the same equipment as in the OP, $3.40/Wt DC, which is 55c/Wt better. Looks very competitive, the installer has many positive reviews on Yelp. I typically take them with a grain of salt, especially the ones that lack substance, but in this case they seem to contain enough details to be convincing that they come from people with real experiences.

They propose a larger 10.2kW DC system that covers 95% of my total consumption, including EV usage, for the last 12 months. While it will likely cover most of my needs and provide protection from future SCE pricing games, I'm not convinced I need that much power with a TOU/net-metering to zero-out, or close to, my monthly bill. Short of sitting down and crunching all data myself, is there an agreed-upon ballpark percentage of total usage that works well for TOU with net-metering, considering most of the usage is shifted to off-peak and super off-peak?

[gvl]

Thanks, this is very good info. Great point on EV charging but my EVSE is hard-wired to the dedicated EV TOU meter, so to get that baseline credit on EV charging I'd need to rewire it to the main panel or use my portable EVSE to charge at night. Might as well just undersize the system a bit to get that baseline allocation credit on non-EV usage, right? One perk of a dedicated EV meter is that it has 11c/kWh rate until noon, so if you're generating excess energy at a higher-priced TOU-A rate at 30c/kWh from 8am to noon and charging at the same time you're generating 19c credit for each kWh that ends up in the EV battery under net-metering, at least this is how I understand it works. I get it it is just semantics but still interesting.

As for TOU-D-A/B availability, the footnote says "There are a limited number of enrollments available for this rate plan", which makes me think the T will be open for enrollment longer than A/B.

[sensij]

130 deg - Generation Value = $3215, Baseline cost = $421, net generation = $2793
220 deg - Generation Value = $3518, Baseline cost = $423, net generation = $3096
310 deg - Generation Value = $2808, Baseline cost = $417, net generation = $2391

With TOU-D-A, note that if you size your system to cover all of your non-EV loads, and then your EV consumed roughly the baseline allocation each month, the baseline cost shown above becomes a credit, and you are effectively charging your car for $0.01 / kWH. TOU-D-A and TOU-D-B are newer than TOU-D-T, and with the shifted peak hours, I would guess they are likely to outlast TOU-D-T.

TOU-D-T

130 deg - $2669 generated
220 deg - $2910 generated
310 deg - $2209 generated

I set up the model assuming very favorable generation (very low system losses), producing over 11000 kWh from a 6 kW array. Under these conditions, about 1.7% of energy is lost with clipping. Please do not use these numbers to justify the absolute price of your system, they really need to be evaluated against what your bill would be with consumption included. As a relative comparison between array orientations, I think it could be helpful.

The spreadsheet I'm using is a modification of what InsaneOctane posted in his thread, with the most significant change being the inclusion of daylight savings time adjustments.

[gvl]

Sure, that kind of analysis works well for the TOU-D-A plan, which has a straightforward energy value in each time of use. It doesn't work quite as well for the TOU-D-T plan which has a complicated forumla to determine when you move from level 1 to level 2 pricing based on how much net usage you have throughout the month. TOU-D-A seems to be favorable for several people here and in other forums that have posted about running the numbers, so I'll get back to you in a bit with an estimate.

What is your zip code, and what tilt / azimuth's do you want to see?

The baseline allocation credit on TOU-D-A must complicate things as well but likely not as bad as the tiered structure on TOU-D-T. I suspect that TOU-D-T will work better in my case due to the earlier on-peak window and the SE direction of my roof, and also that it'll allow me to run my A/C from 6-8pm on the off-peak rate. I have a EV TOU meter so I get 11c for charging my EV at night anyway, so the benefit from the super-off-peak rates on TOU-D-A should be minimal. However I think I should still try to get on TOU-D-A first as my understanding is it will be phased-out and probably sooner than later, I can always switch to TOU-D-T in the future but not the other way around once the A plan is no more.

I'm in 91377, tilt is 23-degrees, azimuth is 130 for SE, 220 for SW, and 310 for NW. Thanks!

[sensij]

One complication for this method is that my hourly usage will be significantly different after a switch to TOU, as I will need to pay attention as to what and how much I use during on-peak, mainly the pool pump and the A/C. As a half-measure a way to optimize the layout just in terms of generation that yields most credits based on the price per kWh during particular time and constraints of a particular site would be at least somewhat useful, I think.

Sure, that kind of analysis works well for the TOU-D-A plan, which has a straightforward energy value in each time of use. It doesn't work quite as well for the TOU-D-T plan which has a complicated forumla to determine when you move from level 1 to level 2 pricing based on how much net usage you have throughout the month. TOU-D-A seems to be favorable for several people here and in other forums that have posted about running the numbers, so I'll get back to you in a bit with an estimate.

What is your zip code, and what tilt / azimuth's do you want to see?

[gvl]

If you have an estimate of your hourly usage for the past year, forum member InsaneOctane put together a spreadsheet that helps compare the different SCE plans. I've been making some modifications to it that will help it be more friendly for cut and pasting estimated production data from PVWatts or SAM, and hourly usage. I doubt many (any) installers have worked through the details well enough to offer a very informed opinion.

My guess is SE will outperform NW, but we could run a model and see.

One complication for this method is that my hourly usage will be significantly different after a switch to TOU, as I will need to pay attention as to what and how much I use during on-peak, mainly the pool pump and the A/C. As a half-measure a way to optimize the layout just in terms of generation that yields most credits based on the price per kWh during particular time and constraints of a particular site would be at least somewhat useful, I think.

[sensij]

What about placing some of the panels on the NW side (area 1)? It gets plenty of sunshine in the afternoon, but obviously not in the morning. Bad idea? Do installers have estimation tools that allow them to find the optimal layout in based on the TOU schedule?

If you have an estimate of your hourly usage for the past year, forum member InsaneOctane put together a spreadsheet that helps compare the different SCE plans. I've been making some modifications to it that will help it be more friendly for cut and pasting estimated production data from PVWatts or SAM, and hourly usage. I doubt many (any) installers have worked through the details well enough to offer a very informed opinion.

My guess is SE will outperform NW, but we could run a model and see.

[gvl]

What about placing some of the panels on the NW side (area 1)? It gets plenty of sunshine in the afternoon, but obviously not in the morning. Bad idea? Do installers have estimation tools that allow them to find the optimal layout based on the TOU schedule?

[thejq]

One thing you might want to consider is tilt mount, so you get either south, or south west exposure from a SE facing roof. It has been talked about many times but I'm not sure about the cost.

[gvl]

Try this: lots of room, no shade --->> LG280 etc. w/ string inverter(s). Face as many south as possible. In San Diego etc. $3.50/$3.5/Watt for that combo ought to be doable and different enough to save your guy some face when he swallows on price, provided you think he's worth it and feel comfortable with him as your vendor. Low buck for its own sake is false economy. Fair and tough negotiating is good business. If he wants your business help him with an opportunity to lower his price by slight changes that result in a better system and savings for all.

On the other hand, get any other quotes ? It's just business.

9,500-10,500 kWh/yr. ought to be doable. Much more might be a stretch.

I'd not recommend using PVWatts the way Thejq suggests.

My guy is super-flexible and will put whatever components I want in the system if he can get them, for me it is just a matter of figuring out the most optimal solution using current technology and the specifics of my site in terms of $$$ that also gives me room for future expansion while making sure he is not overcharging me. I'm working on getting additional quotes.

[J.P.M.]

Try this: lots of room, no shade --->> LG280 etc. w/ string inverter(s). Face as many south as possible. In San Diego etc. $3.50/$3.5/Watt for that combo ought to be doable and different enough to save your guy some face when he swallows on price, provided you think he's worth it and feel comfortable with him as your vendor. Low buck for its own sake is false economy. Fair and tough negotiating is good business. If he wants your business help him with an opportunity to lower his price by slight changes that result in a better system and savings for all.

On the other hand, get any other quotes ? It's just business.

9,500-10,500 kWh/yr. ought to be doable. Much more might be a stretch.

I'd not recommend using PVWatts the way Thejq suggests.

[gvl]

I think you could get an equivalent system for a bit less with some shopping...

In December, user JD31 shared in this post some quotes.

LG280's were about 0.25 / W more than Hanwha panels, and LG280's should be probably at least 0.10 / W less than 300's. I think paying $3.50 - $3.75 / W is reasonable for the 300's if your SE roof doesn't have space for something less efficient, depending on the installer.

$3.50 - $3.75/W with Enphase M250s? They are about $1500 more for a 6kW system than the Solar Edge 7600 that jd31 was quoted for. I should have no problem finding room for less efficient panels as the roof is huge, I should probably do that. Sounds like my guy is more or less in the ballpark, I suppose paying $0.20 extra per W on a 6kW system to someone I can trust is not too bad of a concept?

[sensij]

No, due to reasons that deserve a separate topic the panel had to be taken care of previously. Just need to install the panels drop solar feed on the panel, that's it. You think it is too high for the equipment spec'd or in just general I can spend less for an equivalent system with less expensive components?

I think you could get an equivalent system for a bit less with some shopping...

In December, user JD31 shared in this post some quotes.

LG280's were about 0.25 / W more than Hanwha panels, and LG280's should be probably at least 0.10 / W less than 300's. I think paying $3.50 - $3.75 / W is reasonable for the 300's if your SE roof doesn't have space for something less efficient, depending on the installer.

[thejq]

PVWatt says I should get 8710 KWh with "premium" and "0%" loss. But my total so far is about 10% higher than that. So maybe I'm a little optimistic and weather has been nice, but 9500 KWh is probably doable ... I'm hoping But we digress ...

[gvl]

Does that price include a main service panel upgrade? If so, it is slightly on the high side, but still pretty good. If it does not, you might want to shop it around a bit more.

No, due to reasons that deserve a separate topic the panel had to be taken care of previously. Just need to install the panels and drop solar feed on the panel, that's it. You think it is too high for the equipment spec'd or in just general I can spend less for an equivalent system with less expensive components?