6kW system in Agoura Hills

[gvl]

Yes I factored summer.. We are in Murrieta so climate is similar to yours although we get a nice cool breeze in afternoons which you dont get being in agoura. I am very familiar with your area lived in Thousand Oaks most my life.

Last summer in Temecula we hardly ran the AC but we were able to deal with 80 deg temps inside, not everyone can. Even with running the AC here and there i will have plenty of juice. I didnt deal with degredation aside from whatever the pvwatt default was... Over time the kids will move out of the house so our demand should decline, of course that isnt for another 20 years haha.

Gotta get the spreadsheet out and factor it all in to figure it out. For me, TOU-A was the best plan and a 5.1 system was more than sufficient. If I get rid of my car it will be slight overkill but I think we will probably keep the ev long term now.

My A/C was on almost full-time August-September last year struggling to keep the temps inside the home at 78F, without the A/C the temps on the second floor were 90+ F on certain days, few can deal with that Usage was 1500 to 2000 kWh during those months. I hope solar panels will keep the roof cooler which should help with the A/C usage in the summer. My usage for winter months is consistent with yours.

Need to get to the spreadsheets, but I get a feeling 7kW ballpark is what I need to 0-out my current bill with controlled approach as to when to use big loads. Adding 3kW will pretty much allow me not to worry what to run and when, while also providing a slightly better $/Wt cost ratio plus room for expansion like a 2nd EV 2-3 years down the road, which is quite likely given the promises about improved battery technology materialize. The payback period will likely be about 1.5 years longer which is worse but not the end of the world either. And on top of it, as they've already shown, SCE may screw up EV customers with undersized solar/TOU by enforcing less favorable TOU rates any day while making it more difficult to add additional capacities in the future. Decision, decisions.

[Gmoney!]

I feel your pain I was going through the same issues.

As I suspected you area is hotter. Do you have a new or older home? Insulation might provide cheaper alternative.

I am not planning on a second ev, prefer to keep one car gas for now in case there ever is an issue with power outage etc.

[gvl]

I feel your pain I was going through the same issues.

As I suspected you area is hotter. Do you have a new or older home? Insulation might provide cheaper alternative.

I am not planning on a second ev, prefer to keep one car gas for now in case there ever is an issue with power outage etc.

It is a 1970 tract home, my understanding home builders of that period did set the bar really low in terms of construction quality. The same huge flat SE roof area I plan to use for solar install is exposed to the sun from the early morning and during hottest hours of the day, so I think it is to blame for the heat build-up. There is insulation in the attic and walls, but I suppose there is room for improvement. We will definitely keep one gas car, but my daughter will start driving in 3-4 years, so the plan is to give her our Leaf as I suspect its resale value will be close to that of popcorn by that time and I might be able to get my hands on some new EV tech

[gvl]

So I wrote a little program that parses SCE hourly usage and pvwatts hourly generation estimates and ran it against my actual usage for the last 12 months, even for that non-TOU-optimized usage a 8kW should have generated enough credits to bring the total close to $0, so 10kW is definitely an overkill. While I don't expect to be able to significantly change my usage patters a better plan it seems is to install a 8kW system and save $4k after incentives, and invest $2k into a variable-speed pool pump that can probably save me another 2000kWh annually, and since it is quiet I can use it during super off-peak and save even more.

[J.P.M.]

It is a 1970 tract home, my understanding home builders of that period did set the bar really low in terms of construction quality. The same huge flat SE roof area I plan to use for solar install is exposed to the sun from the early morning and during hottest hours of the day, so I think it is to blame for the heat build-up. There is insulation in the attic and walls, but I suppose there is room for improvement. We will definitely keep one gas car, but my daughter will start driving in 3-4 years, so the plan is to give her our Leaf as I suspect its resale value will be close to that of popcorn by that time and I might be able to get my hands on some new EV tech

Tract homes may get a bad rap, but they aren't usually thought of as good examples of energy conservation's latest/greatest.

[gvl]

I've just realized I'm missing at least an hour of early sunshine every morning due to some hills to the East side of my home which is going to cost me 1000 kWh or so annually. Sounds like my plan to size the array smaller isn't going to work out after all.

[J.P.M.]

I've just realized I'm missing at least an hour of early sunshine every morning due to some hills to the East side of my home which is going to cost me 1000 kWh or so annually. Sounds like my plan to size the array smaller isn't going to work out after all.

Depending on your orientation, I doubt losing the 1st. hr. in the A.M. will cost you 1,000 kWh/yr. More like about half that much or so.

Keep the use reduction goals in place.

[gvl]

Depending on your orientation, I doubt losing the 1st. hr. in the A.M. will cost you 1,000 kWh/yr. More like about half that much or so.

It's more than 1hr I'm afraid. For example today PVWATTS thinks I should be generating 0kW@5am, 1.5kW@6am, 3.2kW@7am, and 4.7kW@8am AC from a 8kW DC system, and there was absolutely no sun on the roof until 7:30. Approximating linearly I would miss about 5kWh of production today. I don't know how this will be distributed over all months, but I suspect the duration of shading will not be constant.

[sensij]

Among other things, PVWatts doesn't use daylight savings time. What it thinks is 6:00, is 7:00 right now. I would suggest getting a better understanding of that tool before using it this way. Get a good shade analysis, ask an installer to preform a SunEye measurement at your installation site.

[J.P.M.]

It's more than 1hr I'm afraid. For example today PVWATTS thinks I should be generating 0kW@5am, 1.5kW@6am, 3.2kW@7am, and 4.7kW@8am AC from a 8kW DC system, and there was absolutely no sun on the roof until 7:30. Approximating linearly I would miss about 5kWh of production today. I don't know how this will be distributed over all months, but I suspect the duration of shading will not be constant.

OK, try this:

1.) Run PVWatts with correct orientation.
2.) Use the hourly output.
3.) Download to a spreadsheet.
4.) Get the totals of hourly output for each hour of a TMY, or for the first few hours as needed.

My guess is the first hour's total estimated total output for the year will be something like 5-8% of year's total estimate for all hours, +/- a bit.

[gvl]

Among other things, PVWatts doesn't use daylight savings time. What it thinks is 6:00, is 7:00 right now. I would suggest getting a better understanding of that tool before using it this way. Get a good shade analysis, ask an installer to preform a SunEye measurement at your installation site.

Thanks, considering the DST it is not as bad then. Still learning...

OK, try this:

1.) Run PVWatts with correct orientation.
2.) Use the hourly output.
3.) Download to a spreadsheet.
4.) Get the totals of hourly output for each hour of a TMY, or for the first few hours as needed.

My guess is the first hour's total estimated total output for the year will be something like 5-8% of year's total estimate for all hours, +/- a bit.

Turns out it is even less, considering my math is not too much off. For a 8.1kWh DC array PVWATTS estimates 12,031kWh annual AC energy. I came up with only 415kWh AC generated (3.4%) for the next 2 hours after the last 0-reading in the morning, more like first 1.5hr of sun on average? Assuming P(H) is the first non-0 predicted power output this is the formula I used for a daily estimate:

Energy = P(H) / 2 + (P(H) + P(H + 1)) / 2

[J.P.M.]

Thanks, considering the DST it is not as bad then. Still learning...



Turns out it is even less, considering my math is not too much off. For a 8.1kWh DC array PVWATTS estimates 12,031kWh annual AC energy. I came up with only 415kWh AC generated (3.4%) for the next 2 hours after the last 0-reading in the morning, more like first 1.5hr of sun on average? Assuming P(H) is the first non-0 predicted power output this is the formula I used for a daily estimate:

Energy = P(H) / 2 + (P(H) + P(H + 1)) / 2

I don't remember your az./tilt, and each sit. is diff., but for my array in zip 92026, 118.75 deg. tilt, 195.75 deg. az. :

Using SAM #'s (TMY3, Miramar), yearly long term est. as % of yearly total output with no shading by (365 ) hr. increments ending each day at:

0600 P.S.T: 0.04% of year's total. (<4 kWh/yr.)
0700 P.S.T. 0.7% of year's total.
0800 P.S.T. 3.2 % of year's total.
0900 P.S.T. 6.9 % of year's total.

Your mileage will vary from mine and they'll both vary year/year. While your hourly % will vary from mine for your location, I'd guess the general trend may be similar.

PVWatts output for your location is left as an exercise for the reader.

Looks like they might be close given your 3.4% #. It is, after all, no more than an estimate.

[gvl]

Among other things, PVWatts doesn't use daylight savings time. What it thinks is 6:00, is 7:00 right now. I would suggest getting a better understanding of that tool before using it this way. Get a good shade analysis, ask an installer to preform a SunEye measurement at your installation site.

They performed SunEye measurements today and say there is no shading, I know there is. Should SunEye have picked up 3-5% early morning shading due to moderate hills a mile or so from home? I suppose it may be due to the deficiencies of the tool, like it can detect a shade from a tree or a house nearby, but the hill contours are pretty low and not as contrasty so they go undetected.

[J.P.M.]

They performed SunEye measurements today and say there is no shading, I know there is. Should SunEye have picked up 3-5% early morning shading due to moderate hills a mile or so from home? I suppose it may be due to the deficiencies of the tool, like it can detect a shade from a tree or a house nearby, but the hill contours are pretty low and not as contrasty so they go undetected.

If the max. hill elevation angles are less than the solar elevation angle for the corresponding azimuth angle, the hills will not cast a shadow at the location of interest. Get a sun path diagram for your location for Dec. 21 that shows solar elevation angles as f(time) and measure (estimate) the hill elevation angles with a protractor. Compare the two.

[gvl]

If the max. hill elevation angles are less than the solar elevation angle for the corresponding azimuth angle, the hills will not cast a shadow at the location of interest. Get a sun path diagram for your location for Dec. 21 that shows solar elevation angles as f(time) and measure (estimate) the hill elevation angles with a protractor. Compare the two.

I can see homes further away from the hills getting sunshine in the morning while my street gets none, isn't it enough to say that sun elevation angles are less than that of the hills? I think they either didn't use the tool correctly or it is an inherent limitation of the tool.

EDIT: they just got back to me saying sun access is 97%, I suppose they may have considered it as no shading as compared to other situations and it is close to my pvwatts hourly analysis