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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. -
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.Leave a comment:
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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!Leave a comment:
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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.orgLeave a comment:
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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.JPGLeave a comment:
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TOU for SCE in Southern California analysis
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:
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.
Leave a comment: