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

[bluebolt]

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]

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]

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.

 

[LectricBill]

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]

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]

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]

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.

 

[iletric]

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]

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!

 

[Airbesar]

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.

 

[Tttait]

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

Yes, but...

I need to be able to fully recharge the car overnight anyway as that's how we use it, at least some weekends. That forced me into a level 2 charger at home. Going level 2 puts me in a situation where I always charge off peak.

In Southern California the rate differences are much greater. I was on TOU actually anyway when I got the Bolt, because we had just put in Solar. Again the SoCal rate structure helped us a lot there too. My Solar is paying me back at 18% per year, pretty much guaranteed minimum. When we sized the system I had them add a couple extra panels so that we could switch over to 99% electric driving in the household and still cancel out the electric bill. It was a great deal for me - but again SoCal has different pricing structures.

Anybody in Socal who is thinking about solar feel free to send me a PM for more details on that part.

To your question, even without the Solar TOU could be a great deal depending on how your rates work. Another option may be to ask about installing a dedicated meter just for your car charging plug. Some power companies will set you up with a separate meter at a reduced electric rate if it's exclusively for charging your car.

 

[BoltyMcBoltFace]

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 think your neighbor got ripped off, unless maybe he got Tesla shingles and was willing to pay for the looks.

I paid $8k for solar over two years ago and it's covered all of my use (admittedly my bill only averaged around $70/month). I've gotten a small check from Southern California Edison each year for my over-production. That's about an 8-year payback.

I switched to TOU after getting a Spark EV and the financial benefit was marginal at the time, but I wanted to get locked in before I got the solar. Now with the solar and 2 EVs to charge overnight I'm definitely far ahead on TOU. Without solar, the cost/benefit will come down to how much of your use you can shift to that off-peak period and what the rates are, and it won't make sense for everyone.

 

[sgt1372]

Without solar, the cost/benefit will come down to how much of your use you can shift to that off-peak period and what the rates are, and it won't make sense for everyone.

I've got similar estimates for solar as my neighbor and a switch to TOU just doesn't make sense for me.

 

[oilerlord]

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.

Something doesn't add up, or he got boned on the system overall. With incentives, $26K should buy a LOT of solar in SF. Unless he installed a Tesla solar roof or a SunPower system, it's not too difficult to get a well designed / good quality system installed for ~$2.00 per watt. That's 13kW DC!

I did a quick & dirty estimate on the NREL/ PVwatts site for a 13 kW system installed in SF, 45 degree tilt, pointing 180 south, and at 15 cents per kWh.

Your neighbor is saving a LOT more than 100 bucks per month, and the ROI should be ~9 years.

 

[sgt1372]

Your neighbor is saving a LOT more than 100 bucks per month, and the ROI should be ~9 years.

Well, that's what he told me. No reason to lie and I'm in no position to audit him. I'll just have to take his word for it.

Just not interested myself.

 

[oilerlord]

No accusations expressed or implied...and as i mentioned, he may have been taken to the cleaners and/or installed a premium system above $4.00 per watt to push the payback to 20 years. When I started looking at solar a few years back, the major solar players were quoting me 30-35 year ROI's (and with a straight faces). I get that there's more to installing solar than saving money, but doing it shouldn't be tantamount to lighting it on fire either.

 

[gpsman]

I looked into it (Bay area, CA) and TOU does NOT make any sense for me. It would be MORE expensive.

In the 7 months I have owned the car, I have found countless public chargings stations, most of them FREE!

I have charged at home 1 time, and just for 4 hours.
In 7 months!

I have paid for DCFC a few times when traveling farther than 200 miles from home. But in total, I have spent about $120 to drive 8,500 miles.

And I have invested $0 in equipment. My only charger is the one that came with the car.

One of the FREE community 6.6 kw chargers near my home is solar powered also. So free and green.

 

[oilerlord]

TOU does NOT make any sense for me. It would be MORE expensive.

In the 7 months I have owned the car, I have found countless public chargings stations, most of them FREE!

I have charged at home 1 time, and just for 4 hours.
In 7 months!

I have paid for DCFC a few times when traveling farther than 200 miles from home. But in total, I have spent about $120 to drive 8,500 miles.

And I have invested $0 in equipment. My only charger is the one that came with the car.

One of the FREE community 6.6 kw chargers near my home is solar powered also. So free and green.

Interesting that in one of your prior posts back in July, you mentioned that you "ONLY" use the included 120v EVSE, and were one of the biggest advocates that most people can easily get by on 120v charging at home.

The 120 VAC cord that comes with the car is very useful.

If you drive 1 hour a day, like most people do, you can put in 130 miles per day. More than you use. WITHOUT spending a dime on expensive equipment.

I drive about 1000 miles per month.
I ONLY use the free 120 VAC cord.
I can get free 120 VAC power at work too.

As it turns out, you really don't use 120v charging at all, and actually depend on L2/L3 charging for your day-to-day needs. I remember we had a debate about if this. I'm (still) of the opinion that L2 charging is essential, but you advocated "most" people only needed to use the included 120v unit. Seems to me the only reason you "didn't spend a dime on expensive equipment" is because you're using it elsewhere, and it's free. Clearly, TOU (or any plan specific for charging your EV) doesn't make sense for you because it costs more than free.

Anyway, it's just an interesting contradiction to a conversation we had a couple months back. It's great that you have countless, free L2 available to you. Some of us don't have that luxury, and instead rely on L2 charging at home.

 

[BoltyMcBoltFace]

oilerlord wrote

I'm (still) of the opinion that L2 charging is essential,

I'm going to differ with you on that. For some people it will be essential, but for many it won't be. Charging overnight on 120 can easily give 50+ miles of range, and that's plenty for daily driving for many people.

I've been driving EVs for over 4 years, and just got rid of my gasser. I have two L2 EVSEs at home - both still in the boxes they came in. Someday I'll install one of them, but I haven't felt the need yet. Sure, I'll use free public charging if it's there, but I certainly don't rely on it - they're too likely to be full around here.


2016 Spark EV
2017 Bolt EV

 

[joe]

oilerlord wrote

I'm (still) of the opinion that L2 charging is essential,

I'm going to differ with you on that. For some people it will be essential, but for many it won't be. Charging overnight on 120 can easily give 50+ miles of range, and that's plenty for daily driving for many people.

I agree with this. My commute is 95 mi/day and I do fine on 120 V. I usually make up almost exactly what I lost, and that's with 8hrs of work and 3-4 hours of commute.