bluebolt
Posts: 33
Joined: Sun Sep 10, 2017 9:15 pm

has anyone found success with TOU (time-of-use) rates at home?

Fri Sep 22, 2017 2:19 am

I estimated the cost to charge my Bolt at home, so that I could ascertain whether switching to TOU (time-of-usage) rate would be favorable. To my surprise, the calculations indicate that I'd be worse off switching to TOU.

Note: I have only a 110V socket to charge the car, but my belief is that the cost will be the same for any voltage -- only the speed of charging will be different.

Eversource electricity generation rates for eastern Massachusetts are listed here:

www.eversource.com/Content/docs/default-source/rates-tariffs/ema-greater-boston-rates.pdf

I live in metro Boston, and my rate is the default A1 residential rate, so according to the document above, my electricity-generation charge is close to a dime per kWh (kilowatt-hour), give or take. This matches what I see on my electric bill. Also on my electricity bill, I can see that my electricity-delivery charge is also about a dime per kWh, give or take. This amounts to a fixed-rate electricity charge of $0.20/kWh, which stays constant across all seasons and all times of day.

The Bolt's battery capacity is 60 kWh, so the cost for me to charge the entire battery from home (recognizing that this takes many hours at 110V) is 60 kWh * $0.20 / kWh = $12. Paying $12 for a range of 250 miles amounts to 1/3 of what I used to pay for gasoline with my previous ICE, so charging at home is already very favorable under the fixed rate.

Now, if I were to switch to the Eversource TOU rate, which is the A5 residential rate in the document above, then the total charges become:

Summer (June-September): $0.33/kWh peak, $0.15/kWh non-peak
Winter (October-May): $0.25/kWh peak, $0.15/kWh non-peak

Compared to my current fixed rate of $0.20/kWh at all hours, the TOU rate seems very unfavorable. The nighttime price decreases 5 cents, but the daytime price increases 5 to 13 cents. On a 110V line, the maximum amount of battery that I can charge is around 20% of total capacity, so if I charged all night, every night, I would save (60 kwh * 20%) * $0.05/kWh * 7 days/week = $4 per week savings for electric-vehicle charging. Meanwhile, judging from the typical amount of my electric bill, my daytime charges would go up by at least $3-$8 per week (depending on the season). The less frequently I charge the car at home, the worse the imbalance becomes.

The upshot is that it seems I'll do much better staying on a fixed rate rather than switching to TOU.

Has anyone found that switching to TOU rate worked in their favor?

globecanvas
Posts: 27
Joined: Sat Jul 29, 2017 4:19 pm

Re: has anyone found success with TOU (time-of-use) rates at home?

Fri Sep 22, 2017 9:16 pm

We also would have ended up spending much more switching to time-of-use billing from Central Hudson (Hudson Valley NY area).

The rates are structured so that you need to have *most* of your usage during off-peak hours in order for it to be a financial savings. It would be suitable for a standalone metered charger, but not for a home that happens to have a charger.

michael
Posts: 651
Joined: Thu Jan 29, 2015 10:13 pm

Re: has anyone found success with TOU (time-of-use) rates at home?

Fri Sep 22, 2017 9:44 pm

It varies widely. I get my power from the Los Angeles Department of Water and Power. They don't give enough advantage to the TOU rates to make up for the risk of big air conditioning bills. Furthermore, they don't respond to requests for change from tiers to TOU, so I gave up on the whole thing.

By contrast, other nearby areas with private power companies (such as Edison) seem to have very large incentives to charge late at night.

So don't assume TOU is necessarily a great thing, might be or might not in your area.
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LectricBill
Posts: 8
Joined: Sat Jun 03, 2017 12:41 am

Re: has anyone found success with TOU (time-of-use) rates at home?

Sat Sep 23, 2017 1:04 am

I went to a presentation on TOU by PG&E (northern California). They explained that their rate was designed to incentivize EV customers to shift their usage so the utility to could spread the load out. They also explained that the rates were designed to net about the same as not shifting, which has been our experience.

We don't have air conditioning and I try to shift power-hogging activities (washer/dryer, vacuuming, dishwasher) to either night time or weekend off-peak hours.

I decided to sign up, mainly to help the utility, not that I'm a big corporate fan, but because they supply my fuel and the presenter seemed like a good guy!

My EV rate is $0.10 KwH and peak rates vary between $0.24 and $0.32 depending on the season. Overall, I think we come out very slightly ahead with their TOU plan and I feel like a good citizen, or something.

eatsleafshoots
Posts: 10
Joined: Thu Sep 21, 2017 5:50 pm

Re: has anyone found success with TOU (time-of-use) rates at home?

Sat Sep 23, 2017 2:17 am

I save a LOT of money on my Xcel TOU plan in Colorado, but the plan is fairly generous.

Summer: 2-6p peak 19c, 9a-2p and 6p-9p shoulder at 11c, 9p-9a off-peak at 8c
Winter: Same as above but shoulder covers 9a-9p, off peak is still 9p-9a

Our electricity is already quite cheap, and I never run A/C up here in the foothills. On average, charging our Volt and Leaf at home results in 75% off-peak, 20% shoulder, and 5% peak consumption which is a huge savings in summer and a moderate one in winter.

globecanvas
Posts: 27
Joined: Sat Jul 29, 2017 4:19 pm

Re: has anyone found success with TOU (time-of-use) rates at home?

Sun Sep 24, 2017 12:52 pm

For reference, our bad TOU plan in NY is about 16c peak, 10c off-peak, but "peak" is 9am to 9pm. The standard rate is about 13c.

(Our utility also charges a fixed $24/month on top of the per-kwH rate, which goes up to $27/month if you choose TOU.)

sgt1372
Posts: 533
Joined: Mon Feb 06, 2017 4:21 pm
Location: SF Bay Area

Re: has anyone found success with TOU (time-of-use) rates at home?

Sun Sep 24, 2017 4:02 pm

2 different TOU plans are offered in NorCal by PGE, which provides a cost comparison calculator (based on your actual usage) to see if either would be cheaper than the Tiered use plan that I am on now.

The calculator determined that one of the plans would be Marvginally cheaper (we're talking just a few dollars, not hundreds) and then I would have to limit my use to specific hours or pay an even higher "off rate" cost.

I decided to pass because I did not want to be time restricted and possibly penalized for using power outside the specified hours for only a marginal cost savings.
Last edited by sgt1372 on Mon Sep 25, 2017 2:18 am, edited 1 time in total.
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iletric
Posts: 172
Joined: Wed Dec 14, 2016 4:50 am

Re: has anyone found success with TOU (time-of-use) rates at home?

Sun Sep 24, 2017 8:01 pm

No matter what you try, you will pay 20-26 cents per kWh summer rate, especially if you have AC at home that has to run during peak. Your cost may go down to about 16 cents during winter rate time with no AC needed.

PG&E has an EV rate deal which is TOU with a supposed discount. Talk to your power company what they have to offer. They realize more and more they are the new "arabs." So we may see all kinds of rate changes in the future.

I plan on getting a big solar on my house to beat the system entirely, as soon as I have the funds for it, since I want Tesla shingles.

sgt1372
Posts: 533
Joined: Mon Feb 06, 2017 4:21 pm
Location: SF Bay Area

Re: has anyone found success with TOU (time-of-use) rates at home?

Mon Sep 25, 2017 2:24 am

iletric wrote:I plan on getting a big solar on my house to beat the system entirely, as soon as I have the funds for it, since I want Tesla shingles.


My neighbor just installed a solar system in his house for $26k and that did not include the extra capacity necessary to charge an EV.

Way too expensive for me to consider just for my normal electric needs. Neighbor said the solar system only saved him $100/mo and at that rate it eould take over 20 yrs to break even.

I should live so long. LOL!
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2012 Mercedes ML350 4Matic
2008 BMW 335i
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2000 Porsche 911 Carrera 4 Cabriolet

Airbesar
Posts: 32
Joined: Thu Jun 02, 2016 2:28 am

Re: has anyone found success with TOU (time-of-use) rates at home?

Mon Sep 25, 2017 5:44 pm

For Sacramento CA folks and as an indicator for what other utilities might offer, here's a website quote from the local utility - SMUD:

"For plug-in electric vehicle owners, there is an additional 1.5¢ per kWh credit for charging your EV between midnight and 6 a.m. every day, all year long. That means that during those hours, the price for all your household electricity is only 7.16¢ per kWh."

I've just signed up for this and will use the 4 hr delay button on the dishwasher so that it runs during the reduced rate period. Regretfully, and my wife especially thinks so, our 30 year old Kenmore washer and dryer still run perfectly but have no delay feature.

The bad news is that the rate under TOU is over 30 cents/kwh for 4-7 PM, weekdays in the summer. At least at around 4, the solar is still producing for the AC. We may play some with the programmable thermostat to cool the house a bit more before 4 and then have the AC go off for a bit after that.

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