Which San Diego Gas & Electric rate plan is cheaper?

I need some help because number crunching what-if scenarios is unfortunately not one of my strong suits. For days I have unsuccessfully tried to figure out whether my current SDG&E residential rate plan or the EV-TOU-2 rate plan (which uses my existing smart meter) would cost me less overall based on a year's worth of my pre-EV electricity usage, as compared to my electricity usage with my Prius Plug-in.

I have had my Prius Plug-in since early March. Since then I have remained on my standard SDG&E residential rate plan because if I change, I will be required to stay with the new plan for a minimum of one year. I don't drive my Plug-in Prius every day but when I do, relatively few of the miles I drive with it are straight EV, because of its very limited all-EV range. Even though my rate plan does not save me any money for doing so, I re-charge it using the car's timer after midnight.

Unfortunately, all I have to show for my frustrating efforts is a stack of print-outs on my desk from my SDG&E online account. These represent my daily electricity use from March 17 - 25, 2011 and the same days in 2012. I have no choice but to print out daily reports because only SDG&E's single-day reports (not the weekly or monthly or annual reports) break down a customer's residential electricity usage by time-of-day, which is how the EV-TOU-2 rates are applied (Super Off Peak, Off Peak, Peak and Off Peak).

In contrast, all but the SDG&E daily reports and my past SDG&E bills (several of which I also printed out), only show overall monthly totals. On my monthly bills these are only broken down by baseline, 100%-130% of baseline, 131%-200% of baseline and more than 200% of baseline for a month - not by the day. Therefore there is no way I can determine how much I would have paid for the same bills over the period of one year if they were calculated under the EV-TOU-2 rate plan unless I look at at each of the 365 days individually, somehow manage to extract the data for each of the four time intervals used in billing under the EV-TOU-2 rate plan, add them all up and then compare them.

To accurately compare what I would pay under each of the two plans for a year (which is the minimum time period SDG&E will let customers sign up for the EV-TOU-2 rate plan), I would have to compile data from each of the four time periods within each day for each of my 365 daily SDG&E usage reports. How on earth am I or other new EV owners supposed to do that?

I was hopelessly confused when I tried to make sense of SDG&E's charts: "Total Electric Rate for the EV TOU(and 2) and DR rates to understand the prices for energy under both billing mechanisms."

Surely SDG&E has the ability to devise some sort of computer program to crunch the data and compare the two different rate plans, given a household's past electricity use, to see which would be the less expensive way to go. Then all SDG&E or, if necessary, I would have to do is add to that my very recent, increased electricity usage between 1AM and 4AM (which is when I have set my Prius to recharge), and I'd get the answer I need to make an informed decision before I commit to a one-year minimum rate change.

Failing that, I have been told that a utility company in the LA area will allow someone to sign up for their equivalent to SDG&E's EV-TOU-2 rates and after a year, if they determine that the customer would have paid less under their previous rate structure, they refund the difference and allow the customer to return to being billed at their previous rate structure. SDG&E does not offer that, and they do not offer sufficient help to me to do these difficult comparative analyses.

Will someone in our group help me decide whether or not to switch to SDG&E's EV-TOU-2 rates? Thank you.

 

Hi San Diego Mom, and thanks for your reply.

Is this what you need? It is from the "Electric Service" portion of my March 17, 2012 due date bill from SDG&E:

Rate: DR-Residential
Climate Zone: Coastal

Total kWh used: 854 kWh

Tier 1: Average cost per kWh - 14 cents, 303 kWh
303 kWh at baseline ($24.34 at the Rate/kWh of $.08033).

Tier 2: Average cost per kWh - 17 cents, 91 kWh
91 kWh at 100 - 130% of baseline ($9.35 at the Rate/kWh of $.10279).

Tier 3: Average cost per kWh - 31 cents, 212 kWh
212 kWh at 131 - 200% of baseline ($37.47 at the Rate/kWh of $.17673).

Tier 4: Average cost per kWh - 33 cents, 248 kWh
248 kWh at More than 200% of baseline ($48.79 at the Rate/kWh of $.19673).

Sub-total: $119.95 plus $4.38 DWR Bond Charge (854 kWh x $.00513) and $49.43 Winter Electricity Generation (854 kWh x .05788)

Total Electricity Charges: $173.76 plus another $10.61 in fees and taxes

Grand Total: $204.46


For a historical electricity usage comparison, this is from my SDG&E bill due March 19, 2011 - a year earlier:

Total kWh used: 904 kWh (versus 854 kWh on the bill due March 2012)

Baseline: 303 kWh used @ $.07387 = $22.38

1 - 30% (NOT 1 - 130%, as in 2012) over Baseline: 91 kWh used @ $.09526 = $8.67

31 - 100% over Baseline: 212 kWh used @ $.20873 = $44.25

More than 100% over Baseline: 298 kWh used @ $.22873 = $68.16

Total before other charges: $143.46 (versus 119.95 on the bill due March 2012)

Grand Total after all charges: $213.72 (versus $184.37 on the bill due March 2012)

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I took delivery of my Prius Plug-in on March 3, 2012 but I did not start charging it until a few days after that, so I do not yet have a full month SDG&E bill post-purchase. However, I do some printouts of daily comparisons between certain days in April this year versus the same days in April last year. I can definitely see that I am using more electricity between 1 - 4 AM, which is when I have my Prius Plug-in set to recharge.

This is very confusing in terms of figuring out which rate plan I should be using to spend the least amount of money on electricity for my house.

 

I really appreciate everyone's help but I am totally confused.

 

Yes, I am a writer and a photographer. I was a history major in college. I'm not a mathematician by any stretch of the imagination.

I've tried to understand what you are patiently trying to explain to me but I'm afraid that it's gone over my head. It sounds like people are suggesting to me that a Prius Plug-in only costs 40 - 50 cents or so for a full charge when I plug it in to a 120 volt outlet, whereas I am using a ton of electricity elsewhere.

I don't know why I am apparently using so much electricity. I do have an electric dryer but I don't use it more than for three or four loads every couple of weeks. I rarely use my A/C in the summer. A TV is on a lot, if that matters (it is a modern, large flat screen) and I only have lights on in the rooms that I am in at the time. I have a gas hot water heater and furnaces. I use one of those parabolic space heaters and wear a down jacket in the cool winter months. The exterior low voltage lighting is off. I run a pool filter for an outside water feature for 15 minutes per day.

I guess that since my car uses so little electricity to recharge once each day or two, the real issue is whether or not my household electricity usage would be cheaper at the standard rates or the EV (TOU) rate, which I have the option of choosing due to my owning a plug-in Prius. Do you have a sense of what the answer might be to that question?

How on earth are they going to market these cars if it is so difficult for the average person to know how much or how little money they are saving?

 

Here goes. I'll convert SDG&E's bar graph for a 24-hour period. Hopefully this is what you are looking for:

1. A Typical weekday (Tuesday, April 24, 2012) (approximate figures)
to 1AM: 0.9 kW/h
to 2AM: 0.8
to 3AM: 0.85
to 4AM: 0.8
to 5AM: 0.5
to 6AM: 0.5
to 7AM: 0.5
to 8AM: 0.5
to 9AM: 0.5
to 10AM: 0.5
to 11AM: 0.55
to 12PM: 0.65
to 1PM: 0.7
to 2PM: 0.7
to 3PM: 0.65
to 4PM: 0.7
to 5PM: 1.1
to 6PM: 1.0
to 7PM: 0.9
to 8PM: 0.8
to 9PM: 0.5
to 10PM: .85
to 11PM: 1.3
to 12AM: 1.0

1. A Typical weekend day (Sunday, April 8 2012) (approximate figures)
to 1AM: 0.8 kW/h
to 2AM: 0.8
to 3AM: 1.7
to 4AM: 1.7
to 5AM: 1.6
to 6AM: 0.8
to 7AM: 0.6
to 8AM: 0.7
to 9AM: 0.6
to 10AM: 0.7
to 11AM: 0.6
to 12PM: 0.7
to 1PM: 0.5
to 2PM: 0.5
to 3PM: 0.8
to 4PM: 0.8
to 5PM: 1.2
to 6PM: 1.0
to 7PM: 1.0
to 8PM: 1.0
to 9PM: 1.15
to 10PM: 2.3
to 11PM: 2.0
to 12AM: 1.9

Thanks in advance.