SDG&E TOU Tariffs

[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.

[J.P.M.]

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 my spreadsheets are already out of date!

Which happens on a frequent basis.

[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.

[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.

[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.

[sensij]

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.

[sensij]

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 my spreadsheets are already out of date!

[sensij]

The value of generation and consumption are calculated at the billing cycle (every month). So most likely you will be inside the baseline. The baseline rate reduction should apply to all 3 TOU periods.

OK, let's try to run with this... let's say in a month with 300 kWh baseline, I'm charging 20 kWh per night, for 20 nights out of the month. That is 400 kWh in the off-peak TOU. Let's say my net for the peak TOU period was -250 kWh. How do you think the bill would be calculated?

One possibility
(-250 * peak price) + (400 * off-peak price) + (150 * baseline credit, which is a negative number)

Does this sound right to you?

Another scenario, same 300 kWh baseline, but lots of sun.

400 kWh off peak consumption
-400 kWh net peak

(-400 * peak price) + (400 * off-peak price) + (0 * baseline credit)

One more scenario, let's say I was on vacation and didn't drive the car for two weeks

200 kWh off-peak consumption
-250 kWh net peak

(-250 * peak price) + (200 * off-peak price) + (-50 * baseline credit)

In this scenario, the baseline credit ends up working against me.

If the above is correct, I think it means that the minimum average energy price would occur if the off-peak kWh consumption exceeds the on peak net generation by exactly the baseline allocation. Haven't heard back from SDG&E yet, I'll try them again later today.

[thejq]

No... AB327 more or less prohibits restricting plans to non-solar customers. There are only a few special conditions that can prevent net metering eligibility, but for customers on any of the normal residential plans, net metering is available. You can read more about the net metering terms here if you'd like to understand it better. The TOU-DR and TOU-DR-P plans were just released in February for the first time, so there doesn't seem to be much experience out there with them. SDG&E already knows I have solar, and those plans are available for me to select online.

Good to know they weren't available when I signed up last year. There were just 3 choices before, which made my decision much easier. So according to the document you linked.

Baseline Rates: If the customer is a net consumer over a billing period, the net kWh consumed shall
be billed at the applicable baseline rates up to the billing period’s baseline allowance, with any
excess kWh consumed billed at the applicable non-baseline rates charged other customers in the
rate class.
If the customer is a net generator over a billing period, the net kWh generated shall be valued at the
applicable baseline rates up to the billing period’s baseline allowance, with any excess kWh
generated valued at the applicable non-baseline rates charged other customers in the rate class.

The value of generation and consumption are calculated at the billing cycle (every month). So with TOU-DR most likely you will be inside the baseline. The baseline rate reduction should apply to all 3 TOU periods.

If I understand it correctly, the interesting thing with this plan is that if for some reason (eg. vacation out of town for a month in the summer) you net generated more than the baseline, you will be credited at none-baseline rate which is much higher.

[sensij]

To sum up: I've found separating system revenue from the electric bill, at least initially, gives me a bit more information and helps me see things a bit more clearly. This is a work in progress.

Thanks for the comments. I like the revenue approach, and am guessing that the successor to net metering may eventually require submetering the generation. I find that for some of the more complicated rate plans, the net approach keeps the analysis cleaner than the revenue approach. It is hard for me to grasp when consumption moves into a higher tier and then the generation pulls it back out again, or vice versa in the negative direction. If the net consumption stays solidly in the baseline allocation, a lot of the other problems go away.

I know what you're thinking/hoping, but I think the baseline adjustment credit applies to all three TOU periods. Plus I thought for the solar customers, the only choices are the normal DR, DR-SES and EV-TOU2. Other plans are for non-solar customers. But you should verify.

No... AB327 more or less prohibits restricting plans to non-solar customers. There are only a few special conditions that can prevent net metering eligibility, but for customers on any of the normal residential plans, net metering is available. You can read more about the net metering terms here if you'd like to understand it better. The TOU-DR and TOU-DR-P plans were just released in February for the first time, so there doesn't seem to be much experience out there with them. SDG&E already knows I have solar, and those plans are available for me to select online.

The catch with SDG&E rate plans is that once you switch, you are locked in for 1 year. They have "bill protection" so that if the previous rate plan (DR for me) would have worked out better, you can pay that bill instead. However, compared to the standard DR plan, I think any TOU plan will be better, and there is nothing that protects me if I pick a suboptimal one from the available choices.

With regard to the baseline allocation, it would work best for me if the entire net monthly usage was summed and evaluated against the baseline, and not each individual TOU period. The net consumption is likely to be a positive number, and should benefit from the credit. If the allocation is split up among TOU periods (as SCE does), some periods will be negative and others positive and the effect of the credit will be more mixed.

If you do driving 15k miles per year, you soon will learn your 3.12kW system is way too small even with TOU....

Yeah, no, there is no such thing as too small. 15k mi at 28 kWh / 100 mi is 4200 kWh. That almost exactly doubles my consumption. Even under the DR rate, my net consumption should be Tier 1, but I am thinking that a TOU plan will push my average energy cost even lower than that. As anyone who looks closely at the numbers will say, it is very hard to justify solar to replace energy that costs $0.15 / kWh. *Maybe* I will consider adding a couple panels (DIY) at the end of the year if the justification makes sense, while I can still grandfather the net metering, but I suspect that a TOU plan will, in some form or another, take care of things. I don't *want* 100% offset... if a minimum bill is likely to be the direction the CPUC approves, at least for the next few years, then I might as well pay for some energy with that money instead of just giving it to them.

I'm generally with you however charging nightly on TOU is cheap even if you don't have enough solar, at least 2x cheaper than paying for gas. Better pay the difference than end up with extra unneeded solar if somehow you need to part with the EV due to it not working for your needs.

Yes! Even if I pay for charging at night, the TOU plans have favorable rates, which look to have some legs. Just need to work through the analysis and figure out which TOU plan will be best. Having no A/C makes it easier, since my daytime usage should almost always be net negative, even with shifting peak hours.

[gvl]

I have no idea why you said that, then you should have just pick TOU plan and charging your EV and run AC at night, you be good without solar. How about that? I don't see how solar is relevant to TOU plan.

Charging EV at night is natural for most people, not running AC during the day is not.

[silversaver]

I don't see how AC usage is relevant to EV charging at super-off peak. If your system is not sized right you'll get hit EV or not.

I have no idea why you said that, then you should have just pick TOU plan and charging your EV and run AC at night, you be good without solar. How about that? I don't see how solar is relevant to TOU plan.

[gvl]

TOU is good, but remember you also pay high price during the day when you need the ACs..... I'm just hoping I have enough credit to cover my Summer/Winter usages....

I don't see how AC usage is relevant to EV charging at super-off peak. If your system is not sized right you'll get hit EV or not.

[silversaver]

I'm generally with you however charging nightly on TOU is cheap even if you don't have enough solar, at least 2x cheaper than paying for gas. Better pay the difference than end up with extra unneeded solar if somehow you need to part with the EV due to it not working for your needs.

TOU is good, but remember you also pay high price during the day when you need the ACs..... I'm just hoping I have enough credit to cover my Summer/Winter usages....

[gvl]

You will find out more about sizing and benefit of little larger solar when you start driving EVs. I start to like Solaredge inverter especially go larger unit with easier expansion feature on mutiple roofs. It seems oversizing the inverter has no affect to the performace.

If you do driving 15k miles per year, you soon will learn your 3.12kW system is way too small even with TOU....

I'm generally with you however charging nightly on TOU is cheap even if you don't have enough solar, at least 2x cheaper than paying for gas. Better pay the difference than end up with extra unneeded solar if somehow you need to part with the EV due to it not working for your needs.