Estimates of system revenue using old vs. new T.O.U times and rates.

[CharlieEscCA]

I believe Charlie's tariff rate schedule is either DR-SES or EV-TOU.

I am indeed on DR-SES as of my bill period that started May 10, 2017.

In my spreadsheet I track both $ on the TOU plan (these dollars are actual credit or cost per day, then summed into the billing period and compared with my bill) and $ of what my use would have been if I was on a tier rate structure (I'm not convinced if I didn't have solar I would have gone to TOU as long as DR was available to me).

The SDGE actual data (which is what really counts in terms of a bill from SDGE) only provides net usage. But, because I have wattNode consumption data and SolarEdge production data, I am able to compute my estimated overall kWh use per day and compute what my bill would have been under tier rates. My bill for the period ending July 10 (not even hitting the real hot months yet) calculated at $529 under tier rates, a frighting thought. Because of TOU favorability, the July 10 bill actually yielded a $10 bill and added over $100 to my credit that is now being used (my August bill at this time looks to draw probably $100 or more from my current credit balance of over $300).

But JPM is so right -- everyone's situation is different; and if they are wise they will figure out how and what numbers to run, and then make a decision that is proper for them. Note I did not say right, because there is no absolute right or wrong.

[J.P.M.]

I am indeed on DR-SES as of my bill period that started May 10, 2017.

In my spreadsheet I track both $ on the TOU plan (these dollars are actual credit or cost per day, then summed into the billing period and compared with my bill) and $ of what my use would have been if I was on a tier rate structure (I'm not convinced if I didn't have solar I would have gone to TOU as long as DR was available to me).

The SDGE actual data (which is what really counts in terms of a bill from SDGE) only provides net usage. But, because I have wattNode consumption data and SolarEdge production data, I am able to compute my estimated overall kWh use per day and compute what my bill would have been under tier rates. My bill for the period ending July 10 (not even hitting the real hot months yet) calculated at $529 under tier rates, a frighting thought. Because of TOU favorability, the July 10 bill actually yielded a $10 bill and added over $100 to my credit that is now being used (my August bill at this time looks to draw probably $100 or more from my current credit balance of over $300).

But JPM is so right -- everyone's situation is different; and if they are wise they will figure out how and what numbers to run, and then make a decision that is proper for them. Note I did not say right, because there is no absolute right or wrong.

Looks like you generated ~ what you used (~~1,455 kWh use +/- a bit for 06/10- 07/10 ??). Got that from backing into how much use a $529 tiered bill would have caused ~1,455 kWh, and my SWAG for what a decent 8.04 kW system around here will actually put out for the same period, based on actual insolation and weather, of ~ 185 - 190 kWh per STC kW, = ~ 1,500 kWh or so kWh for that period using actual data for an 8.04 kW system for the same 30 day period ending 07/10.

So (and leaving NBC calcs out of all this for the time being and for the sake of focusing on one thing at a time while recognizing NBC still needs to be resolved), if your usage and generation roughly balanced one another for the period, and because of DR-SES being a true T.O.U., if you banked some excess $$, that would/could mean that, because of T.O.U., your average cost per kWh for what you used for the period is less than the average income per kWh of the electricity your system generated for that same period. That, FWIW, is also a useful or maybe interesting way to look at the benefit of time shifting usage away from peak T.O.U. times as well as how system size can be reduced in the design stage by estimating the effect of such time shifting.

Under the current (and probably soon to be old) DR-SES rates and times, the average value of a kWh of electricity as a bill offset in inland San Diego, using PVWatts, 10 % system losses and a south facing 20 % slope is, by my reckoning ~ $0.2823/kWh generated over the course of a year, again, using the current DR-SES rates and times. Under the possible new rates and times for DR-SES, if what SDG & E writes it wants come to pass, that average value per kWh generated under such a new set of rates and times will be something like ~~ $ 0.2159/kWh generated. That can be useful info.

To the degree that time shifting of loads can lower the average cost/kWh of what gets billed, such lowered of the per kWh costs will allow systems to be reduced in size for the same total net bill effect.

That $0.2159/$0.2823, BTW, is where I got the SWAG/ 1st cut approximation of an ~ 23 % or so reduction in system cost effectiveness, or ROI reduction, or ~ a 23 % increase in system payback time using the moron method of payback calc.

I also find it of interest to note that the new (proposed) DR-SES rates and times produce an average per kWh value of system generation ( $0.2159/kWh generated) that is lower than any of the current DR-SES hourly rates (lowest = $0.22171/kWh), and only a bit less than the lower per kWh rates for the new (proposed) DR-SES schedule (lowest = $0.19813/kWh).

[CharlieEscCA]

Looks like you generated ~ what you used (~~1,455 kWh use +/- a bit for 06/10- 07/10 ??). Got that from backing into how much use a $529 tiered bill would have caused ~1,455 kWh, and my SWAG for what a decent 8.04 kW system around here will actually put out for the same period, based on actual insolation and weather, of ~ 185 - 190 kWh per STC kW, = ~ 1,500 kWh or so kWh for that period using actual data for an 8.04 kW system for the same 30 day period ending 07/10.

Last bill, June 8 to July 9. "Estimated" production, 1565 kWh (SolarEdge reported value, so likely less than this). Estimated consumption the $529 on the tiered plan was based upon was 1454 kWh.

It's plausible my estimated consumption might be 3% high, as I have to go through some corrections to get to my estimated consumption (namely my SolarEdge generation minus SolarEdge reported consumption [which comes from the wattNode] never matches with the SDGE actual net for the day -- but this isn't all SolarEdge being off as there is are garage circuits not measured by the wattNode sub panel location that have a freezer in a hot garage and outside lighting). Bottom line, the estimate on what would have been tier rate bills is close enough for me.

And this next bill August 8th is on track for what would have been a $600+ tier rate bill (actuals through 7/31 and estimate of 8/1 to 8/8 based on forecast and kWh used on similar days). All I can say is when the A/C is on, my reported consumption rate jumps up 6 kW (6 kWh per hour) -- and by mid afternoon the A/C is on continually until the outside has cooled off enough to turn it off and open 22 windows and one skylight for overnight cooling. Thermostat is set to 78, windows are opened at 77. House will be at 65 to 72 in the morning depending on how bad the day gets. But, we haven't been in the upper 90's or 100's yet -- so when those days come, we'll have to see when and if windows get open. Based on how the A/C chews through kWh, and the wife now isn't upset with me because the A/C isn't turned on, the sizing this at the 8.04 kW DC appears to be the correct call.

[J.P.M.]

Last bill, June 8 to July 9. "Estimated" production, 1565 kWh (SolarEdge reported value, so likely less than this). Estimated consumption the $529 on the tiered plan was based upon was 1454 kWh.

It's plausible my estimated consumption might be 3% high, as I have to go through some corrections to get to my estimated consumption (namely my SolarEdge generation minus SolarEdge reported consumption [which comes from the wattNode] never matches with the SDGE actual net for the day -- but this isn't all SolarEdge being off as there is are garage circuits not measured by the wattNode sub panel location that have a freezer in a hot garage and outside lighting). Bottom line, the estimate on what would have been tier rate bills is close enough for me.

And this next bill August 8th is on track for what would have been a $600+ tier rate bill (actuals through 7/31 and estimate of 8/1 to 8/8 based on forecast and kWh used on similar days). All I can say is when the A/C is on, my reported consumption rate jumps up 6 kW (6 kWh per hour) -- and by mid afternoon the A/C is on continually until the outside has cooled off enough to turn it off and open 22 windows and one skylight for overnight cooling. Thermostat is set to 78, windows are opened at 77. House will be at 65 to 72 in the morning depending on how bad the day gets. But, we haven't been in the upper 90's or 100's yet -- so when those days come, we'll have to see when and if windows get open. Based on how the A/C chews through kWh, and the wife now isn't upset with me because the A/C isn't turned on, the sizing this at the 8.04 kW DC appears to be the correct call.

Thank you. I'm in a similar boat on "sailing" the house. Usually open up and ventilate ~ 1900 - 2000 hrs. most nites until I get up ~ 0500 hrs. or so. July's total electrical usage was 963 kWh or so, of which 451 kWh was for A/C. July this year had an average temp. at my house that was ~ 5 deg. F. warmer than the average of the prior 9 July's I've lived here. Solar generation was 922 kWh for the month, 176 kWh/STC kW. That's 90.3 % of the PVWatts long term estimate, but that's w/6% system loss parameter and ~ 5% shading that PVWatts doesn't account for.

This year's July production was 92.9%, 101.5% and 100.3 % of the prior 3 July's production, 2016, 2015, 2014 respectively. Note that your production was similar or slightly better than mine, as was, I suspect, Senjij's, giving more strength to the idea that a Sunpower system, even one using an optimized design, and very carefully installed, will not perform any better than other quality equipment that's professionally and/or carefully installed.

[sensij]

Well, sonofa-----. Rev. 2 of the proposed GRC Phase 2 decision just came out, and instead of 3 pm - 9 pm for peak, 4 pm - 9 pm is now proposed. Time to recalculate. It seems likely that revenue takes a hit, but if consumption is factored in, the net effect could be murkier.

http://docs.cpuc.ca.gov/PublishedDocs/Published/G000/M193/K644/193644189.PDF

[J.P.M.]

Well, sonofa-----. Rev. 2 of the proposed GRC Phase 2 decision just came out, and instead of 3 pm - 9 pm for peak, 4 pm - 9 pm is now proposed. Time to recalculate. It seems likely that revenue takes a hit, but if consumption is factored in, the net effect could be murkier.

http://docs.cpuc.ca.gov/PublishedDoc.../193644189.PDF

Yea, I saw that. They also put voting on all of it from 08/10 to 08/24.

I recalced the revenue and it came up a noticeable amount lower, but I'll wait until the 08/24 to make any statements. I suspect the tendency will be for bills to drop bit given the time of day and being at the early part of a lot of daily A/C usage, but that will likely be a lot less predictable user/user than system revenue decreases.