TOU for SCE in Southern California analysis

[insaneoctane]

So, I am on a journey for anyone interested in joining me...
I am an engineer (aerospace) who is sometimes too analytical for my own good.
I have a fairly new 6kw system that has been operating since Nov 2014 and am already wondering if I should be on TOU.
I have been trying to comprehend SCEs various rate structures and I am convinced that they must be purposely complex to keep people from understanding how they work. Much like the tax codes or legal-speak.
Here is the link to sce rate schedules:

https://www.sce.com/residential/rates/special-time-of-use.htm

To view the TOU rates, scroll down and expand the "+View pricing for these TOU rates" section...
I have several questions, but I will start with the basics

1. I am finding (so far) that the TOU-D-A plan is best for me. This plan shows 1 "on-peak" rate and 2 "off peak" rates (super, regular) . The on peak claims it is "On-Peak: 2 p.m – 8 p.m. (non-holiday weekdays only)" . So, my question is during weekends what is the rate? There are 2 off peak rates. I obviously could assume the super off peak rate, but my experience tells me assuming might cost me money!

2. For the TOU-D-T plan, I would assume that if I find myself in tier 2 (past 130% baseline) that the higher price of electricity is only for consumption not for generation? Or, said another way, they never pay me at anything but tier 1 rates, but can charge me for tier 2 if applicable?

I have tried to model all 3 plans in Excel and have a pretty cool spreadsheet going (it's a little complicated too) and would like to invite anyone interested in checking it in some way as a second set of eyes (more validation of answers seem right, less checking formulas) . I have used my actual hourly gen/consumption data for the last 3 months. I don't think the spreadsheet is perfect yet, I am still making tweaks...but it's getting there.

[insaneoctane]

Here are some examples of output.
pic1 is summary showing A with best savings
pic2 is feb 1 data
pic 3 is 1st week of feb

tou-ex1.PNG
tou-ex2.jpg
tou-ex3.JPG

[DanS26]

Here is how I approached my TOU analysis problem.

I installed a TED5000 system and set its calculations up for the TOU but let the utility on regular rates. Simple comparison over a few months and seasons will tell you the best plan to be on.

Yes, you have to spend some money on the TED but probably less effort in the long run. The TED will also provide you with lots of other great information and can be interconnected to your solar system and output data to third party analysis platforms such as PVOutput.org

[insaneoctane]

Here is how I approached my TOU analysis problem.

I installed a TED5000 system and set its calculations up for the TOU but let the utility on regular rates. Simple comparison over a few months and seasons will tell you the best plan to be on.

Yes, you have to spend some money on the TED but probably less effort in the long run. The TED will also provide you with lots of other great information and can be interconnected to your solar system and output data to third party analysis platforms such as PVOutput.org

I have a TED5000 installed currently and LOVE it. That is what provides the data that I have analyzed over the last 3 months. There are 3 TOU plans and 1 tiered plan available to me, hence the spreadsheet analysis. If my numbers are accurate and it is already lucrative for me to be on TOU-D-A after Nov, Dec and Jan it seems like it will only get better as production increases. But I do need to see how power hungry my family of 5 is during the summer months when they aren't in school. I could get hourly data in the past from sce... But I still am learning about my solar output. To put it in perspective, I saw my systems best day ever (so far) this week and it's only Feb!

[J.P.M.]

Iso: Welcome to the world of spreadsheets and electric rates. Get set for 8,760+ row spreadsheets. From someone who's been there for several years, a few thoughts, FWIW:

1.) I'm more knowledgeable about SDG & E than SCE rates and tariffs, but they seem to have some similarities.

2.) As much as a PITA as it is, I've found using the POCO/CPUC tariff sheets to be easier to work with that the stuff the POCO's put out for general public consumption. It makes for more info, and that makes things a bit more complicated in that sense, but they do get less muddy and so a bit more manageable and lots more accurate.

3.) I too have wondered about what seems to be the unnecessary complication and also the lack of clarity or any explanation of how to calculate a (projected) bill, tiered, T.O.U, or other billing scheme. After lots of work. I've got the SDG & E tiered rates figured out, but it was a daunting task made slightly easier the more I understood the cryptic logic/nomenclature.

4.) Assuming an array is sized for <= the annual load, the best way I've found to work on T.O.U. rates and resulting bills (so far - a work in progress) is to break it into two $$ streams. Using the PVWatts hourly output estimate, SAM, or some other estimator and the T.O.U. schedule under consideration, the yearly sum of (the hourly array output) X (the T.O.U. rate for that hour) will estimate potential annual revenue for that array. Given that the T.O.U. rates, array size and (for the purposes of this analysis) the annual array output is (assumed) fixed, the annual income from an array is fixed.

5.) Setting that income stream as constant for the purposes of this analysis, that income will be decreased by the second stream - household usage. The cost of that usage will be a function of 2 things: How much electricity is used and when it is used. That usage amount and when it occurs is the part you, I or any other consumer can control to some degree, and for me, that history is avail. in 15 min. increments from SDG & E.

6.) If prior hourly usage is available, it's possible to calculate what a prior annual bill would have been if you were on T.O.U. Obviously, one will be higher than the other, or (unlikely) equal.

6.) Getting an estimated, future or average T.O.U bill can be tricky. First off, it is a bit of a PITA, but possible. Second, and probably more troublesome, is the problem of determining what actually constitutes an average or representative set of 8,760 hourly usages.

7.) Assuming an average, representative hourly usage data set (admittedly of questionable accuracy, if any) can be generated, an estimated annual T.O.U. bill can be generated. As above, that estimated bill can be compared to the tiered bill, and a decision made, go/nogo on T.O.U.

8.) The idea of economically optimum array sizing prior to buying solar with T.O.U. becomes trickier than with tiered rates not only because usage charges are f(time of use) but also, among other added variables, system revenue will be more variable due to increased sensitivity to weather variability, making the marginally optimal array size a bit fuzzier than it already is. More work in progress for me. Film at 11 on that one.

9.) A couple of things that might happen when comparing T.O.U. vs tiered rates: One is that system (array) revenue with T.O.U may be higher, but not as much higher than the billing increases due to customer usage pattern(s), tiered, vs. T.O.U. Or system revenue may increase and billing may go down, again due to customer usage pattern(s). A 2 X 2 matrix may be useful in sorting this out. I'd suggest that system "revenue" will generally do up with T.O.U., but billing MAY go up more, or less, depending on usage pattern(s).

10.) In any case, under common scenarios, treating the array output as an income stream separate from the billing stream expense seems to make things more manageable for me and a bit easier to make some sense of.

11.) All this is, of course, trumped by what rate reform in the near/mid term future may have in store.

Take what you want/need of the above. Scrap the rest.

[sensij]

You might want to check out this thread. The OP put together a pretty decent spreadsheet for comparing the options, and he would probably share it if you are interested. Maybe not the bells and whistles it sounds like you are building into yours, but at least a chance to double check the calcs. If you'd like another opinion on yours, feel free to send it my way.

[J.P.M.]

You might want to check out this thread. The OP put together a pretty decent spreadsheet for comparing the options, and he would probably share it if you are interested. Maybe not the bells and whistles it sounds like you are building into yours, but at least a chance to double check the calcs. If you'd like another opinion on yours, feel free to send it my way.

I'm mostly up to my best intentions in SDG & E rates at this time.

Part of my suggestion was that the POCO CPUC tariff sheets are easier for me to use once I learned how much necessary detail was buried (hard to pull out) in the POCO blurbs that are put out for general information. I'm on board with the lament of POCO's making it hard to decipher just what's going on. Using the tariff sheets gets you more info, but that info seems a bit easier for me to comprehend. Not a shortcut, but better.

Over the years with this rate business, I've found what I early on considered extra bells and whistles are almost always necessary pieces of information. Example: Getting the proper billing schedule. Such things are fairly straightforward to put together. If a computer Luddite such as me can do it and get it right, I'm sure anything anyone else who has an eyeball and a balloon knot can do at least as good, and easily superior. I just piggybacked on the tariff sheet information and logic, converted to rows and columns.

I double check the tiered calcs in two ways: Every time there is a change in any of the factors that are part of the overall rate(s), usually quarterly or more often, and when I compare neighbors' actual bills against what I calculate as an estimate. Of all the folks in my HOA I don't know of any on T.O.U. at this time. That seems in line with something I read and wrote about from some testimony from an SDG & E exec. that said something like some fraction of 1% SDG & E's residential rate payers were on T.O.U. My memory might be off on that one. As I wrote, my T.O.U. stuff is ongoing - the rates are fairly easy, the usage is the devil part.

Sort of an aside on the POCO's making it hard to figure out what to do: I wonder if they (the POCO's ) have considered that if they made it super easy to ACCURATELY calculate a bill for usage in various ways that it might just work to their benefit in the sense that it will be easier for customers to see just how cost ineffective it can be to offset an entire electric bill vs., say a 70-80% offset. And so, maybe, be able to see that to offset the last ,say, $400-$500/yr. in electric bill will take the system cost up by, maybe say $5,500 x .7 = $3,800, moving their system breakeven time out a couple or 3 years. If so, maybe folks would buy more appropriately sized systems (smaller ?), or at least have access to more information on which to base their decisions.

[silversaver]

I have tried to calculate and estimate my annual consumption, but more I do it the more I know I'm off. My consumption were all different from past 3 years. So I take a easier route by add few more panels. I'm in TOU-D-A plan now and I'm glad SCE has made my life easier with showing all 3 (peak, off peak and super off peak) totals.

I have TED5000 and not everyone has it.

First, I think you should understand your solar arrays and determine when is your main output hours. Luckily I have my solar running more than 1 year and my solar arrays were facing SWW 245 deg which TOU make sense to me. Since I already have all the datas (SCE and TED5000), I know what I needed is covering my Winter heating consumption. (everyone were different on this)

So I pick Jan 10th, 2015 which I used about 48kWh from SCE and my solar produced about 9kWh. (see the picture. the info is free on SCE.com)

Base on the graph, my main consumption fall under super off peak from 10 to 8am (11 cents) I would prefer to use high credit to cover the lower rate during super off peak.

Summer usage can be tricky.... Look at the 3rd graph. My solar produced 36kWh but still withdraw 64kWh from SCE.... When both ACs are on, thing can be real ugly. I think I can only bank during Spring......

[insaneoctane]

What I think I may do, is to see if I can download past hourly consumption data from SCE. Then try to get a pvwatts estimate that I'm happy with (I don't have this yet because I've got some shading that is worst in Winter, so I'm not sure if it's mostly gone by Summer solstice? It makes for predicting my output tough) and fill that into my spreadsheet. I'll somehow make a column to note source (measured vs estimated) and upload the spreadsheet here for anyone that wants to take a look. Currently, I don't have the standard tiered calculations in the spreadsheet, they are in another ROI spreadsheet that I'm monitoring, so although I have the "actual bill" showing, that is simply input not calculated based off my current tiered plan.
I appreciate the conversation and the interest/willingness to check each others work! JPM, I need to look for this more detailed POCO/PCUC sheet for SCE...

More to come. I kind of think that I might have an error currently since my spreadsheet shows that my last bill I paid $30.29 (would have been $170.83 w/o solar) would only cost me $6.45 on TOU-D-A and I only produced 584kWh for those 32 days. Again, I'm expecting my production to increase up to another 50% or so by peak season (rough estimate), so I guess I was thinking TOU would punish me more during Nov-Feb...

[SoCalsolar]

I'm interested

Both SDG&E and SCE allow you to download your usage using "Green Button" it will download your usage for up to 13 months? or a specified recent time period in 15 minute intervals. You can get this as an excel file, CSC file, and others I believe. There is work being done on a platform to convert this data into intelligible information. There are some commercially available programs that can utilize this data. Others are working on a consumer facing option using "Green Button Connect" software. I've been considering hiring a software developer to program something that would automatically gobble up the data and spit out something of a best case worst case scenario of your current usage. Hopefully be able to add solar scenarios to determine the best outcomes. Wasn't sure anybody would be interested. Sounds like at least 5 of us would be interested.

[J.P.M.]

FWIW, I started with the smallest increments available, 1 kWh and 1 hr. increments. ( then 15 min. increments came along). That allows the most flexibility but requires the biggest spreadsheets. Stick with the hourly PVWatts and remember, PVWatts is an estimator NOT a predictor. Better yet, use SAM.

Meant as a respectful suggestion, I started with tiered rates and got familiar with all the nuances and devils the POCO hides in plain site. I found it best to start at the beginning with my bill, the tariff sheets, figuring a bill and then getting a calculation to match what my actual bill shows. Then, I did the same for prior bills.

There are sites that get close to my tiered stuff, but leave out the billing period adjustment. I'd be wary of paying some spreadsheet guru to do this stuff. No offense, but after doing it for a while, you'll know enough to shake your head at the foolishness and amateurishness of some things called accurate. Some stuff is decent. Most of it leaves some stuff out. Truth to tell, mine probably does too, but I fix 'em as I find'em and I'm finding far fewer as I go. Biggest PITA now is keeping the rates current.

[scrippsbruin96]

TOU with EV and Solar

My appologies if this question was already asked and answered but I can't seem to find it anywhere.

Does the solar output match TOU tiered pricing?

For example, I'm in SDGE territory and during the summer from noon to 6 PM the cost per kwh is 0.49/kwh, does that mean power generated during that time is counted at 0.49 per kwh too?

I'm currently on the EV-TOU-2 pricing plan under SDGE. To me, it would only make sense to stay under the TOU pricing structure if the above is the case.

[sensij]

My appologies if this question was already asked and answered but I can't seem to find it anywhere.

Does the solar output match TOU tiered pricing?

For example, I'm in SDGE territory and during the summer from noon to 6 PM the cost per kwh is 0.49/kwh, does that mean power generated during that time is counted at 0.49 per kwh too?

I'm currently on the EV-TOU-2 pricing plan under SDGE. To me, it would only make sense to stay under the TOU pricing structure if the above is the case.

Yes, the "net metering" agreement that is protected for 20 years from your system start-up means that the credit you receive for energy generated is the same as what you would have paid for that energy if you bought it. Specific rates, tiers, or hours of TOU may change, but the basic agreement that you get full retail value of your generation will not.

[J.P.M.]

My appologies if this question was already asked and answered but I can't seem to find it anywhere.

Does the solar output match TOU tiered pricing?

For example, I'm in SDGE territory and during the summer from noon to 6 PM the cost per kwh is 0.49/kwh, does that mean power generated during that time is counted at 0.49 per kwh too?

I'm currently on the EV-TOU-2 pricing plan under SDGE. To me, it would only make sense to stay under the TOU pricing structure if the above is the case.

Probably/likely. The other side of the coin is to use as little power as possible during peak hours. Maximize income, minimize expense = more for you.

[scrippsbruin96]

Probably/likely. The other side of the coin is to use as little power as possible during peak hours. Maximize income, minimize expense = more for you.

someone told me the same before, but just thought it was too good to be true since during the summer time during the bulk of the solar generation SDGE would be "buying" electricity at almost 50 cents per kwh while EV owners would "buy" electricity at just 1/3 of that cost during max off peak hours.