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I'm also in SDG&E's area, but I think most of the CA POCOs will be following similar strategies.
The 20 years sounds great, but SDG&E will surely change some things to reduce any benefit you get from it. Obviously rates change, but SDG&E also has a plan to shift the "peak" hours to later in the day, 2pm to 9pm. This means much of your generation will be shifted to semi-peak and much of your consumption to peak. As of now, it's not clear what parts of net metering will be grandfathered, but I would bet the time shift will apply to all TOU customers, just like the new rates.
Also, it appears SDG&E wants to make TOU mandatory for all customers by 2018. With TOU hours changing, rates changing, monthly fees, and all customers shifting to TOU, the ROI on solar will likely be significantly lower.
Of course, none of the above is approved yet, but it seems the customer rarely comes out ahead with the CPUC.24xLG300N+SE7600 [url]http://tiny.cc/n7ucvx[/url]Comment
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The 20 yr. grandfathering is written into current legislation, so it is approved at this time. As you write, things will change. I'm quite sure the big 3 CA IOU POCO'S never wanted it in the first place and will do what they can to minimize its impact on profits. To the extent capitalism is a reality, evil or not, it's still just business and you can count on it.
One way to minimize the individual impact of anything the POCO's do starts something the POCO's cannot control: individual users internalizing the concept that the less electricity is used, the less impact POCO rate shenanigans can have on your situation. Use less. You'll save money, and the POCO's won't get in your knickers quite so far. Added free bennie for tree huggers: you'll leave a smaller amount of spoor in your wake that does bad stuff to the environment. Walk the walk.Comment
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So, I haven't had a lot of time to play with the spreadsheet. I have tried to look at things per JPM's suggestion of (+) and (-) separately. Sometimes that helps, other times it is confusing. For example, with my TOU-A credit, it only applies to energy consumed and only upto baseline. So as long as my cumulative monthly consumption is below baseline, I get a $0.10 credit for each kWh CONSUMED that hour. My production effectively reverses that credit. Fun stuff. Anyway here is a graph of how my January & Feb gen/consumption would have broken down in TOU-A for SCE:
JAN
tou-ex_graph.JPG
FEB
tou-ex_graph2.JPG
Once I figure out how I want to slice/dice the data and fix it to work on all 3 TOU options, I'll share the xls. Now that I have the data, figuring out how to look at it has been very challenging! For example, if you look at the second graph (Feb), and look at the credit column, you'll see both positive and negative credit. I produced more green "off-peak" than I used, so I net "undid" $15.76 work of credit, but in the other two categories, I used more than gen and was able to produce $35.66 credit....net credit of $19.90. Similar to comparing gen/consumption....if I were to graph a single stack of net gen/consumption, I'd have some periods (off-peak) of negative and other (super off-peak and on-peak) of positive, so the net gen/consumption wouldn't just be in a single direction, but some above the line and others below. It's honestly weird and I'm really struggling figuring out what I *want* to see right now. Also, I am not including the fixed $ in these graphs, haven't decided how I want to show that either.Comment
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Starting to get the data to where I might believe it. I'm surprised with my findings. I finally had to bring in the standard RATE-D calculations to see them in comparison. I still need to update my calcs (certainly check/validate) for the other TOU schedules, I'm really only looking at TOU-D-A because it looked like it was the better one for me.
So, here's the surprising results (TBR)...
After installing 6kW system to try to offset ~100% of yearly kWh usage (which was just under 10kWh last year), I've found my neighbors trees are shading my system at sun up and sun down more than I expected, so I'm NOT on track to meet my goal. Current estimates show that I will still pay SCE $273.18 per year with my 6kWh system. Yuck.
The good news now. TOU-D-A shows I'll have a credit of $283.13 for the same period if I've done my math correct. I am using my last year's usage for forcasting the future with no adjustment. For solar predictions, I'm more uncertain since I'm not getting anywhere near PVWatt's outputs for my system. I think the worst is behind me, where my neighbors shading affects me the most during Winter solstice (low sun angle). For my current predictions, I used a 10kWh PVWatt hourly output run and then I applied an 85% factor to each hour. This says my 6kW system will product ~8.5kWh/year. I've had some good outputs lately, I just don't have any confidence because for Nov, Dec, and Jan my generation was close to HALF of what PVWatts predicted. I think Feb was much better at 104%, but I'm just not sure. Anyway here's the graph:
I show 4 curves for TOU ( RED = Usage, BLUE = Production, PURPLE = Credit, GREEN = Net $) and one for standard Rate-D (Tiered, Light BLUE)
tou_analysis_2015.02.28.JPG
Take a look at the graph and see if it passes your smell test. The "credit", purple line, is because on TOU-D-A they give me ~.10/kWh upto 130% of baseline. I also haven't gotten very accurate baseline #'s yet, they'll skew things a bit too. The xlsm file has gotten a bit out of control as I iterate different things (10MB now).
Thoughts?Comment
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Nicely done so far.
One more time: using PVWatts to compare individual months or years will lead to problems. Part of the reason you are not getting anywhere what PVWatts estimated is because your weather is not the same as what PVWatts uses to ESTIMATE LONG TERM OUTPUT..
Do as you wish. I encourage you to continue your work. But, meant as a friendly suggestion, and in the most respectful way possible, IMO, your ignorance of what PVWatts does, how it uses weather data, and its limitations are leading you to false conclusions and incorrect expectations. I'd just as respectfully suggest, read the PVWatts help info screens and also spend about 20 min. reading info on the net about TMY's - Typical Meteorological Years, and how they are generated and their limitations. You have only knowledge to gain and a few miuntes to lose.
Also, I think you mean you used 10,000 kWh last year, not 10, right ?Comment
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Yes, 10,000kWh.
Also, I understand that PVWatts isn't ideal for this, but I really don't know how else to predict my hourly generation. If I had 1 year of past data, I'd just use that and it would be a great starting point for me....but I don't have that. If you have a better suggestion for predicting hourly generation data, I'm all ears!Comment
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My calculations also showed TOU A as better. I think if you can shift most your usage to off peak, TOU A will be the better plan eventhough sce claims TOU D is better for solar owners.
I still didnt understand what this .10 cent credit is? Is it if you stay below 130% of baseline after net metering or just based on total consumption?Comment
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Yah i doubt ill qualify for that. I'll be producing more than consuming during day but that EV will use up a ton at night which i'll buy back at .11 cents but still will probably go over 130%.. Is it calculated monthly or daily?Comment
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Forget about the ears. Now see this:
I appreciate your situation. Mine isn't a whole lot different.
Given the uncertainties involved, PVWatts is probably as good as most TOOLS for estimating LONG TERM OUTPUT OVER MANY YEARS.
Get the hourly PVWatts output for your system on a spreadsheet. If you're familiar with SAM, that's probably better. Or, run both and take your best shot at something that makes sense to you between the two.
IF you DEFINE a PVWatts hourly estimated output for one year as a long term average output for your system, and multiply each hour's output by that hour's rate from a POCO T.O.U. tariff schedule(s) of your choice, you will have an estimate of annual average revenue from you system. That revenue will then be constant regardless of how much you use, provide the system is not oversized. You can adjust that for annual rate increases as your needs and/or desires dictate. Because the weather will vary, revenue for some years will be more, some less.
For T.O.U., one BIG consideration is to think about and decide (define really) just what an average year's usage will, or ought to look like in terms of quantity of kWh used and time of use, and have a fair probability of being representative of your lifestyle. Once you do that, for better or for worse, high/low, right /wrong, you will be able to estimate the cost of that usage. Again, some years will be more, some less. The variables of changing lifestyles, not to mention how the POCO will probably mess with the peak/off peak times in the future will always compound the uncertainty, but that's life. Sue me.
The difference in the two yearly totals, revenue vs. expense will be how much you'll owe or pay. Again, some years will be more, some less. Think long term and think flexible.
I realize SCE has a dizzying tariff schedule and they are a lot less than forthcoming about helping to make sense of the mess, but the logic above in some form ought to work.
Basically, it's figuring out revenue and expense separately and going from there. Maybe a PITA, but I'm pretty sure the tools exist to do it.
I've got the SDG & E schedule TOU - SES on a spreadsheet of 8,760 + rows. A TOU with bins would be more difficult, but doable.
Take what you want of the above. Scrap the rest.Comment
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Am I missing something here?
You already said you have a TED5000 system. If you set up the TED for solar capture and have TOU set up properly then it will be obvious over a period of a few months and a few different TOU plans which one is advantageous for your household usage patterns. Why reinvent the wheel?
Download TED data to spreadsheet and do a boatload of analysis.Comment
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Although I failed to comment yet, on my post above (#23), something interesting about the graph:
3rd month (March), shows that I consumed more than I generated (682C vs 623G), yet I got a credit (-$23.79). This illustrates the power of the TOU if it can work for you...
FYI, in case it's not obvious, the "used" or "consumed" amount is the raw consumption amount, NOT net (gereration does not effect the raw amount).Comment
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