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    JRW Automotive Journalist

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    Location:
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    Your Vehicle Year:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    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.
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    Sandiegomom New Member

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    Hi Jrw, what tier do you normally end up in?

    When i get home tonight I will see if I still have the spreadsheet I created to calculate costs based on the hourly data. It wasn't worth it for me but I have very low usage.
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    JRW Automotive Journalist

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    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)

    --------------------------

    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.
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    Sandiegomom New Member

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    I also need a typical weekday and a typical weekend day for your on-peak, off peak, etc. The "gotcha" with the tou plan is if you have a lot of load during the day.
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    JimboPalmer Tsar of all the Rushers

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    Quick thread jacking, My wife and I will be in San Diego on April 27th, in case we can do a mini meet.

    :focus:
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    Sandiegomom New Member

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    JRW - from my back-of-the-napkin calcs, you will save money in the winter regardless (by about $40/month even if all of your usage except charging is at peak hours - "winter" is Nov 1 through Apr 30), but summer is close, depending on when you use your power. Let me know your on-peak and off-peak numbers for a summer day if you have them. I will try to convert the spreadsheet to Google docs in the next day or two so others can use it.

    ~Disclaimer~ I am a professional in the industry, but make no guarantees about my 6am math abilities or projected cost savings!
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    Sandiegomom New Member

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    JimboPalmer - welcome to America's Finest City! What part of town will you be in and when?
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    Rebound Senior Member

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    Your home uses about twice as mine, so you might want to look into the causes of that. A common cause is an electric clothes dryer; switching to a gas dryer may pay for itself quickly, and you may have incentives available through your power co which defray some of the costs. To understand which rate plan to switch to, try to figure out what consumes the most power in the home, and at what times are those things running. A typical big power draw is AC, but I wouldn't think you ran it much in March, did you?
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    rogerv Senior Member

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    Location:
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    A Kill A Watt device comes in handy for figuring out which appliances are the big energy consumers. You can get one on from Amazon, among other sources. Mine confirmed the 3.1 kHW for a full charge, and the $0.40 I pay for it at my current rate.
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    cwerdna Senior Member

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    P3 - Kill A Watt is awesome. There are some fancier versions now. The original can usually be had for <$20 now. It's one of the best cheap gadgets I've ever bought.
    Well, the OP is almost certainly in a different climate zone than either of us are. See Energy Maps of California.

    Switching to a gas dryer might be impossible if there are no gas lines nearby. We also don't know if the OP has an electric or gas water heater. FWIW, I used 310 kWh last month and 32 therms in a 5 bedroom almost 2500 sq ft house. Admittedily, it's not that fair a comparison as I'm living alone in it and not working at the moment, so I'm home most of the time.

    Agree that the OP should try to figure out what's consuming all the power at home. Kill-a-Watt helps.
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    SageBrush Senior Member

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    Nice modesty, but really unneeded. After all, you have already admitted you are an auto journalist :D

    I'll leave the spreadsheet making to someone else, but I'm pretty confident you will not benefit from TOU:

    You consume about 28 kwh a day, of which *at most* 4 kwh is the PiP. In the summer you may have AC running at night, but most of the year your additional electricity use at night is minimal -- call it another kwh. So 5 kwh each night, which now costs you tier 4 rates of 20 cents a kwh = 80 cents a night, will decrease to perhaps 25 cents a night. (You did not say how much TOU night use is, so I used 5 cents a kwh.)

    So , TOU at night is saving 80 - 25 = 55 cents a night.

    How much is the DAY use cost now ?
    Of 690 kwh
    303 @ .0833
    91 @ .1028
    212 @ .1767
    84 @ .1967

    $88.58
    Average cents/kwh = 8858/690 = 12.83

    From the night, you saved 55 cents. Spread over the 23 kwh/day you use during the day, that is 55/23 = 2.39 cents a kwh. Adding 12.83+2.39 gives us the break-point of 15.22 cents/kwh for TOU consumption during the day. If more than 15.22 cents/kwh, stay away from TOU.
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    SageBrush Senior Member

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    Still cold in the bay area, or is the NG sacrificed in the name of Jacuzzi ?

    My utility bill arrived today: No NG use, 345 kWh electricity. I am *so* looking forward to switching my hot water to NG.
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    cwerdna Senior Member

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    I have to look back over the period in which the bill covered as to the temps. It was very hot over the weekend but just a few weeks before, we had rain, some gusty winds and lightning (pretty rare here).

    There's no jacuzzi here. It's a combination of the water heater and furnace.

    Just like the bill for the month before I posted at http://priuschat.com/forums/toyota-...ctric-bill-up-20-120-145-a-3.html#post1527263, I'm WAY below what similar homes are using for gas and electricity. I'm also below what they call efficient homes.
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    JimboPalmer Tsar of all the Rushers

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    We are in a Hampton Inn at 1531 Pacific highway (downtown?)
    from midnight May 26 to noonish May 28, then on the Carnival Sprint. We have a dinner date the 27th at Cafe 21 at 750 Fifth Ave.
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    bfd Plug-In Perpetuator

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    ^^^
    Downtown/embarkadero. Plenty to do and close to the trolley. Supposed to storm up tonight, though.

    The lake was pretty windy when I was out for a run just now. But it's been unusually warm and humid today!

    Have fun on your cruise!
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    Sandiegomom New Member

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    Hi Sagebrush - the rates that are listed in the detail of his bill are just the transmission & distribution portion of the rate. That's where the tiered rates are for the residential rate - the generation portion is flat. For TOU, it's the opposite. The T&D is basically flat, but the generation varies based on the time of day.

    In order to do this comparison using your method, we will need to use the whole rates (I'll use your kWh values for easy comparison)

    You consume about 28 kwh a day, of which *at most* 4 kwh is the PiP. In the summer you may have AC running at night, but most of the year your additional electricity use at night is minimal -- call it another kwh. So 5 kwh each night, which now costs you tier 4 rates of 29 cents a kwh = $1.45 a night, will decrease to 73 cents a night. (Super off peak/winter is 14.6c/kWh)

    So, TOU at night is saving 145-73 = 72 cents a night.

    How much is the DAY use cost now ?
    Of 690 kwh
    303 @ .14
    91 @ .16
    212 @ .27
    84 @ .29

    $186.14

    Average cents/kwh = 18614/690 = 26.97

    From the night, you saved 72 cents. Spread over the 23 kwh/day you use during the day, that is 72/23 = 3.13 cents a kwh. Adding 26.97+3.13 gives us the break-point of 30.1 cents/kwh for TOU consumption during the day. If more than 30.1 cents/kwh, stay away from TOU.

    The HIGHEST rate on TOU is summer on-peak at 25 cents/kwh.

    Unfortunately it gets more complicated. Your baseline varies between summer and winter, so that will affect your basic residential calculation.

    Here's a good resource for the DR residential rate: http://www2.sdge.com/tariff/com-elec/DR.pdf

    Try this one for EV-TOU-2 (second box):
    http://sdge.com/sites/default/files/regulatory/schedule_ev-010112.pdf
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    JRW Automotive Journalist

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


  18. Offline

    JRW Automotive Journalist

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    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?


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    cwerdna Senior Member

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    Yep, I think you are.

    Your dryer uses a lot when it's running. I can't speak to your A/C (I'd imagine it's central) and I'm sure that uses a lot too. You parabolic space heater likely consumes 700-1500 watts. I can't speak to the pool filter pump. Cooking w/electric stoves/appliances/ovens and non-microwaves for a long time could add a fair amount to your electric bill.

    Do you have a lot of incandescent or halogen lights? If so, are they on for more than a few minutes? If so, look into replacing them w/CFLs or LEDs, except LEDs are generally quite pricey.

    The P3 - Kill A Watt (or one of the fancier ones) that I mentioned will let you measure all the plug loads and determine which are hogs, esp. when turned "off" (in standby).

    The cost complexity issue you mention is made difficult by varying electricity costs and complicated pricing schemes. :(

    Blame the utilities and the ripoff electricity rates in CA. You'd be shocked by the cheap and simple rates at Seattle City Light: Electric Rates & Provisions and fall over at the rates at 2011 Rates.
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    JRW Automotive Journalist

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    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.

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