My $0 SCE bill

[FDJ]

Hello guys. Trying to understand and pick the right Time of Use plan from SCE. My system went online Nov 16 and I have one full month of NEM, where for the billed month of Dec 16 I used 136 kWh. I have a 7.7kW system. SCE has three TOU plans TOU-D-A, TOU-D-B, and TOU-D-T. SCE recommends TOU-D-T for solar system owners. I noticed silversaver above is on TOU-D-A. Is there a general rule of thumb to figure out what plan to choose? Will it make much $ difference? Thanks.

[lemonsocal]

In the sense it might not be oversized, yes.

One way to look at it is to treat the PV array as a revenue producer only, see what PVWatts estimates hourly generation for over one year by hour, modify that for estimated shading losses, which seem kind of high, multiply each hourly output by (each hour's rate minus the non bypassable charges), and sum the 8,7860 hourly revenue generation. That will give some idea of what the array will produce in terms of $$ if treated as a revenue source.

Takes a little work and understanding of the tariff structure you're under, and your shading loss is something PVWatts won't give you, but after that, you can tailor your array size to whatever you see fit with a semi reasonable estimate of the impact different sizes will have on your bill.

JPM: Thanks, I didn't know that I could download the data by hour. I see that the hourly generation in the final column (AC system output) is W. Do I divide this number by 2000 to get kWh? When I totaled the W, dividing by 8,7860 didn't give me the right number.

FFE: For the past calendar year (Jan-Dec 2016), I used ~16,000kWh, and these percentages reflect that entire year: 9% on peak, 23% off peak, 68% super off peak. What do you mean by charging during off peak "to avoid the minimum charge"? Is this something specific to the TOU-D-A plan? Also does everyone get a baseline credit of 300kWh per month on TOU-D-A? Thanks.

The bid for the 7.7kW system included a site eval with a suneye shading analysis getting at the projected annual production of 10,300kWh. 24 panels x 320W each. Tilt 19. Azimuth 220.

[J.P.M.]

JPM: Thanks, I didn't know that I could download the data by hour. I see that the hourly generation in the final column (AC system output) is W. Do I divide this number by 2000 to get kWh? When I totaled the W, dividing by 8,7860 didn't give me the right number.

FFE: For the past calendar year (Jan-Dec 2016), I used ~16,000kWh, and these percentages reflect that entire year: 9% on peak, 23% off peak, 68% super off peak. What do you mean by charging during off peak "to avoid the minimum charge"? Is this something specific to the TOU-D-A plan? Also does everyone get a baseline credit of 300kWh per month on TOU-D-A? Thanks.

The bid for the 7.7kW system included a site eval with a suneye shading analysis getting at the projected annual production of 10,300kWh. 24 panels x 320W each. Tilt 19. Azimuth 220.

Lemon: See my prior post for correction of my screw up on number of hours in a year with apologies.

The last col. in the excel PVWatts hourly output is in Watts. That is, the last column shows an estimate of the system output in Watts that the array will produce over one hour, or Watt-hours. Divide that number by 1,000 to get kWh.

Also, remember, it's only an estimate for the specific hour of the day and day of the month of the specific year used by PV Watts for the model, with most of that irradiance data being synthetic.

See the PVWatts help screens for further information, and remember, it's only a model, not gospel. Far from it.

[FFE]

FFE: For the past calendar year (Jan-Dec 2016), I used ~16,000kWh, and these percentages reflect that entire year: 9% on peak, 23% off peak, 68% super off peak. What do you mean by charging during off peak "to avoid the minimum charge"? Is this something specific to the TOU-D-A plan? Also does everyone get a baseline credit of 300kWh per month on TOU-D-A? Thanks.
.

That is some impressive load shifting! I thought I was aggressive with 15% on peak for the 12 months prior to solar. A quick and easy double checked after you calculate it hour by hour for SCE TOU-A is as follows: You want to produce enough to cover peak plus off peak plus about 35% of super off peak. So for you it would be: 1440+3680+3808=8928 kWh. This assumes that rates don't change which is not realistic. The system you are looking at would be just about perfect to allow for normal increases is use, probable rate changes and reductions in production. The big thing that could change is the ratio of on and off peak rates to super off peak rates. My first SCE bill after solar was $0.3588, $0.2535 and $0.10996. Currently it is $0.33929, $0.27393 and $0.13503. So as the prices get closer I have to work harder to load shift with diminishing returns.

I charged the EVs during off peak three months last year due to a policy that was changed after I had my system installed. The way our bills are calculated allows for a "loop hole" to minimize or avoid the ~$10 per month minimum charge but still get a negative "energy bill" that counts toward the true up. This can only be accomplished by being super detailed and diligent. The big picture is I saved $20 for the year by spending about 3-4 hours a month last year.

[lemonsocal]

FFE: I saw a substantial monthly savings after changing from a regular tiered plan to TOU-B, given my significant super off peak usage. I am really hoping to capitalize on this with solar. But I can see how the benefit from load shifting and solar generation with TOU diminishes as the super off peak and peak rates get closer. That being said, a 100% offset solar sizing is just not feasible for me. Regarding avoidance of the $10 monthly minimum ($120 annually)--perhaps I will let that one go; it sounds like it requires a lot of work / calculation! Thanks for your very helpful comments!

JPM: I understand the PVWatts hourly output table now. It was very helpful to estimate my projected "revenue" from solar. Thank you too!

[J.P.M.]

That is some impressive load shifting! I thought I was aggressive with 15% on peak for the 12 months prior to solar. A quick and easy double checked after you calculate it hour by hour for SCE TOU-A is as follows: You want to produce enough to cover peak plus off peak plus about 35% of super off peak. So for you it would be: 1440+3680+3808=8928 kWh. This assumes that rates don't change which is not realistic. The system you are looking at would be just about perfect to allow for normal increases is use, probable rate changes and reductions in production. The big thing that could change is the ratio of on and off peak rates to super off peak rates. My first SCE bill after solar was $0.3588, $0.2535 and $0.10996. Currently it is $0.33929, $0.27393 and $0.13503. So as the prices get closer I have to work harder to load shift with diminishing returns.

I charged the EVs during off peak three months last year due to a policy that was changed after I had my system installed. The way our bills are calculated allows for a "loop hole" to minimize or avoid the ~$10 per month minimum charge but still get a negative "energy bill" that counts toward the true up. This can only be accomplished by being super detailed and diligent. The big picture is I saved $20 for the year by spending about 3-4 hours a month last year.

Lots like a lot of due diligence there. FWIW, nicely done.

Also, a good example of something T.O.U. rate payers may want to keep in the back of their minds going forward: There's nothing cast in stone about T.O.U. rate differential s or times. They can, and probably will shift around. I'd suspect perhaps some trend of regression toward the mean (with rate differentials between times tending to get smaller), as your rate changes seem to show. Example: Say, 10 years from now, if EV's REALLY take of, and people do a lot of load shifting, the times between say, 11 P.M. and 5 A.M. may well be times of large(r) use, prompting POCO's to boost rates at those times and perhaps lowering midday rates a tad to send what they euphemistically call "price signals" to users. It's hard to the point of being next to impossible to guess with much chance of being mostly right what the future holds, Just something to add to the sizing considerations and not be too surprised if something like that happens.

[FFE]

SCE recommends TOU-D-T for solar system owners. I noticed silversaver above is on TOU-D-A. Is there a general rule of thumb to figure out what plan to choose? Will it make much $ difference? Thanks.

Did they look at your past 12 month useage for your specific situation? If so, that may explain their recommendation. Did you get that recommendation from their website where it claims it is attractive for self generators?

You would have to figure out what works best for you. I find it hard to believe that TOU-D-T saves anyone that load shifts and has an EV money with or without solar compared to TOU-D-A. Over one year before I installed solar I switched from an EV plan to TOU-D-A because I determined it would save me money immediately. JPM described the process to "run the numbers" earlier in this thread. If you get a chance to run them please let us know what you figured out. I would be surprised if anyone with solar could save money with TOU-D-T over TOU-D-A.

[FDJ]

Did they look at your past 12 month useage for your specific situation? If so, that may explain their recommendation. Did you get that recommendation from their website where it claims it is attractive for self generators?

You would have to figure out what works best for you. I find it hard to believe that TOU-D-T saves anyone that load shifts and has an EV money with or without solar compared to TOU-D-A. Over one year before I installed solar I switched from an EV plan to TOU-D-A because I determined it would save me money immediately. JPM described the process to "run the numbers" earlier in this thread. If you get a chance to run them please let us know what you figured out. I would be surprised if anyone with solar could save money with TOU-D-T over TOU-D-A.

FFE thanks for your response. Yes, I got the information from SCE website general explanation of TOU rates. I don't have an EV but do some load shifting by running our pool pump in the morning. I'm going try to figure how to "run the numbers" and post the results.

[J.P.M.]

FFE thanks for your response. Yes, I got the information from SCE website general explanation of TOU rates. I don't have an EV but do some load shifting by running our pool pump in the morning. I'm going try to figure how to "run the numbers" and post the results.

Get ready for some necessary number crunching and digging into the way you are billed. Not meant as a discouragement at all, but getting meaningful numbers from such an exercise takes more digging into tariff structures and POCO billing policies than most folks start out thinking. FWIW, been at it for years and still learning. Basically, GIGO applies.

[wwu123]

I suspect T.O.U. rates and times, particularly times for this conversion, will be responsive to demand. Highly theoretical example: If everyone were to adopt time shifting such that it resulted in a large increase in use at nite, say midnite to 5 A.M, POCOs will attempt to change rates and/or T.O.U. times in such a way as to maximize revenue and /or balance loads.

My overall guess is that things will, as always, regress toward the mean with supply/demand being the driving mechanism. In that example, time shifting by users may well tend to increase off peak rates and also tend to apply less upward pressure on peak time pricing.

To that point, so many people in Hawaii adopted solar (both PV and thermal water heating), that it effectively time-shifted power plant peak demand to the evening. So Hawaiian's Electric's latest TOU plan has peak pricing from 5 pm to 10 pm, and "off-peak" during the day from 9am to 5 pm, with 10 pm to 9am rates somewhere in-between....

I've been trying to get my sister in Hawaii on solar for years - while they didn't get in on the original retail net-metering, they were prepared and slid in for the "wholesale" net metering last year in the few months before HECO shut down net-metering for good (future solar installs cannot send energy back into the grid at all).

[FDJ]

Yes, I got the information from SCE website general explanation of TOU rates. I don't have an EV but do some load shifting by running our pool pump in the morning. I'm going try to figure how to "run the numbers" and post the results.

It took me a little while, but I crunched the numbers for 57 days worth of use. I made some guesstimates using the TOU winter rates found on SCE website. I used 188.88 kWh over the 57 days, with about half of the days being mostly overcast, cutting my solar production. I ran my useage data provided by SCE on Excel and I found for my case TOU-D-A was the clear winner with a -$7.92 charge. The normal Tiered rate estimate was $31.93. TOU-D-B was $55.59. TOU-D-T was $23.47.

[J.P.M.]

It took me a little while, but I crunched the numbers for 57 days worth of use. I made some guesstimates using the TOU winter rates found on SCE website. I used 188.88 kWh over the 57 days, with about half of the days being mostly overcast, cutting my solar production. I ran my useage data provided by SCE on Excel and I found for my case TOU-D-A was the clear winner with a -$7.92 charge. The normal Tiered rate estimate was $31.93. TOU-D-B was $55.59. TOU-D-T was $23.47.

That's 57 days on winter T.O.U. How about summer rates ?

[FDJ]

That's 57 days on winter T.O.U. How about summer rates ?

New system...Just got online mid November. I just called SCE today to TOU-D-A from Tiered effective my next billing cycle, Mar 16th.

[cebury]

This doesn't help you but PGE just implemented a new web usage/billing interface ,which I assume may mean some of backend/intermediate tool changes, because it now allows Solar PV customers to determine the best billing system choice. I've hit my first TrueUp so not sure if it's only for those whom have (likely). But it will do the last 12 months calculation to see if the plan you are on is the least costly plan, just like non-Solar PV customers have been able to for years.

[FFE]

New system...Just got online mid November. I just called SCE today to TOU-D-A from Tiered effective my next billing cycle, Mar 16th.

Like JPM mentioned, you will need to watch your summer rates. As long as you avoid running the big items (things that pump water, heat, cool and Electric Vehicle charging) at peak hours you are usually better off on TOU-A than a tiered rate.

Two examples: My 60% offset system only ends up with 2 months of the year with using more on/off peak than it produces.
I recently spoke to a friend that has 80% offset solar on a tiered rate for 7+ years. I recommended they look into TOU-A. SCE said they would save the $200 per year that they normally pay at true up. They never even tried to load shift and they still could have saved.