Idea for small residential PV system, in California

[inetdog]

I found this too, [ATTACH=CONFIG]2960[/ATTACH], on the same page as the link I just provided. Yikes! "... sized to your historic electric usage, up to 1,000kW." That sounds like a gotcha, meant to prohibit precisely what I'm proposing. That is, tier shaving. If you must install a system sized to provide essentially all of your own power, there's no way to size the system to target the upper tiers . Unless that's wrong, the devil has once again appeared in the details .

In California, the power you sell back is accounted for at whatever the TOU rate is at the time of the backfeed, and the usage tier system for each period is based on usage per month, not instantaneous power use rate.
As a result, everything that you manage to sell back during the day peak hours goes to reduce your monthly usage for that time period, automatically shaving off the top tier. If you generate so much during the days that you have a net sell back for that TOU bucket, your payback rate is also tiered!
So by generating only during the day and using only at night when the whole tier structure is lower priced, you can pile up the credits while still being a net consumer.
The key point is that the tiers are applied separately to each usage period.

To me the line that you are looking at really means that the maximum size allowed for your system will be your historic usage (in kWh per year) or 1000kW nominal output, whichever is smaller. (For a residential user 1000kW (not kWH!!) would be pretty extreme. For a commercial user it might be within reach.)

Some incentive programs may place a minimum size on the system, but I do not think that SCE's Net Metering program does.

[paulrye]

In California, the power you sell back is accounted for at whatever the TOU rate is at the time of the backfeed, and the usage tier system for each period is based on usage per month, not instantaneous power use rate.
As a result, everything that you manage to sell back during the day peak hours goes to reduce your monthly usage for that time period, automatically shaving off the top tier. If you generate so much during the days that you have a net sell back for that TOU bucket, your payback rate is also tiered!
So by generating only during the day and using only at night when the whole tier structure is lower priced, you can pile up the credits while still being a net consumer.
The key point is that the tiers are applied separately to each usage period.

To me the line that you are looking at really means that the maximum size allowed for your system will be your historic usage (in kWh per year) or 1000kW nominal output, whichever is smaller. (For a residential user 1000kW (not kWH!!) would be pretty extreme. For a commercial user it might be within reach.)

Some incentive programs may place a minimum size on the system, but I do not think that SCE's Net Metering program does.

Thank you. I talked to a solar contractor late in the day yesterday, and he confirmed everything you said. So, I jumped the gun by suggesting that "gotcha". This all sounds very good as far as installing a smallish system and tier shaving the high priced tiers.

Regarding my talk with contractor, he said most systems here in SoCal are within the range 3kW to 5kW, and they tend to be sized to produce net metering whereby the homeowner ends up paying his POCO for tier 1 power and producing the rest from the solar PV system. He also said that if the system is sized just right, to best shave the tiers, with all the special credits included as well, the payback can be as low as 3 to 4 years. That sounds "good" but it's only good because California rates are already so ridiculous.

Only about 10% of my usage is in tier 3, and about 21% is in tier 2, so a 300W system would get me out of tier 3 most of the time, and a 1kW system would be enough to shave tiers 2&3 most of the time, and tier 3 all of the time. However, the 300W system is almost pointlessly small because the installation costs would become a larger percentage of the overall cost.

What I'm going to do next is start looking at the total costs of a 1kW, 2kW, and 3kW system. Easy to do once I get my spreadsheet done.