SDG&E TOU Tariffs

[thejq]

Yes, I believe your formula is correct. But the way you wrote it made it as if you're penalized for generating too much (but you're not). So let's simplify it differently. Starting with your formula:
(-250 * peak price) + (400 * off-peak price) + (150 * baseline credit, which is a negative number)
= -250 * (peak price + credit) + 400 * (off-peak price + credit)
this is assuming you're in baseline all the time which is true in your examples.

So scenario 1: -250 * (0.459-0.229) + 400 * (0.360-0.229) = -5.1, or $5.1 in credit
scenario 3: -250 * (0.459-0.229) + 200 * (0.360-0.229) = -31.3, or $31.3 in credit

There you go, penalties disappeared This simplification means any additional consumption in the off-peak is billed at $0.13/KWh as long as your net consumption is in the baseline. Otherwise, the formulation is slightly different.

[thejq]

I spoke with an SDG&E rep. She more or less confirmed the interpretation above. She also said that after the first bill, I can change back to my previous plan, or select a different one. I would not be able to go back to the cancelled plan for 12 mo after that.

I think that is enough to do some modeling this weekend... we'll see which one comes out on top.

I'd be mindful discussing the exact ways to calculate the rates. In my experience, anything resembles algebra is way over their heads.

[sensij]

Ok, I see that we are saying the same thing. I'll run the numbers this weekend. The TOU-DR-P looks likely to be more optimal than the TOU-DR plan, even without considering what should be a peak bonus on RYU days, since the credit adjusted ratio between peak and off-peak is higher (DR-P = 1.91 summer & 1.76 winter vs 1.76 all year for TOU-DR).

The 2.78 & 1.16 ratios of TOU-EV-2 might turn out to be better, while the 2.36 & 1.02 ratios of DR-SES look least favorable. One mitigating factor with TOU-EV-2 is that the Super Off Peak period is only 5 hours long, and my car charge will take longer than that.

In any case, I don't think that the 11-6 pm peak periods will continue to be offered for very much longer, but it will be nice to benefit from it while I can. It will need to be revisited whenever that tariff revision occurs.

[J.P.M.]

New tariffs released today... my spreadsheets are already out of date!

Which happens on a frequent basis.

[sensij]

The TOU-EV-2 plan looks like a pretty convincing winner. With some rough approximations of my usage patterns, I am projecting an annual bill of about $170, not counting the minimum charge since I don't really understand how it is applied in a net metering true-up situation. The DR-SES plan came out to about $300 annual bill, while the TOU-DR plans are $360ish, not counting the benefit from the RYU days, which might be worth $50, but it is hard to count on more than that. The normal DR tiered plan came out to about $560, which seems about right based on my experience with it.

I'll do some more error checking and update this thread again if I find a significant error or change in usage assumptions.

Edit: After a weekend of fighting with the SDG&E site, I was able to download my hourly history for the past year today from their "My Usage" page. That should help improve the accuracy of my projections, were had just been based on usage I've collected myself over the past couple months with the Eagle device.