PG&E TOU Customers: Charge nightly to reduce cost?

[ken830]

It's really way too complicated.

I've had the Tesla for almost three years now, and I've been wanting to go solar. We also have a Rav4 EV. Each car does about 2,000-2,500 miles per month. We have E1 on the house and EVB for the cars. For the past three years, I've been trying to finish the calculations to decide what to do for the shortest ROI... Solar on the E1, solar on the EVB, two solar systems -- one for each meter, combine meters and switch to EVA then add solar... And then what size system for each scenario? It's not an easy calculation when you take into account the various rate plan permutations, tiering, TOU, the weekend vs weekday vs holidays, summer vs winter (and that DST offset twice a year).

I've already got the typical weather-adjusted solar system output mapped out for every hour of every day of the year. and my EV usage is predictable, but I still have more work to map out my hourly usage for every day of the year.

 

[miimura]

It's really way too complicated.

I've had the Tesla for almost three years now, and I've been wanting to go solar. We also have a Rav4 EV. Each car does about 2,000-2,500 miles per month. We have E1 on the house and EVB for the cars. For the past three years, I've been trying to finish the calculations to decide what to do for the shortest ROI... Solar on the E1, solar on the EVB, two solar systems -- one for each meter, combine meters and switch to EVA then add solar... And then what size system for each scenario? It's not an easy calculation when you take into account the various rate plan permutations, tiering, TOU, the weekend vs weekday vs holidays, summer vs winter (and that DST offset twice a year).

I've already got the typical weather-adjusted solar system output mapped out for every hour of every day of the year. and my EV usage is predictable, but I still have more work to map out my hourly usage for every day of the year.

You should start with the historical usage for your home, based on PG&E Green Button data. I have never added in hourly solar data, but that would be an interesting exercise. In my experience, E-1 is never the best choice, but I've never studied a home that uses a lot of A/C in someplace like Tracy or Chico. However, that's not your situation if we're talking about San Carlos.

You should also talk to PG&E about Net Meter Aggregation if you really want to optimize your setup. This is a new system that was started in 2014 that allows a NEM generator to allocate that generation across multiple meters. When I built my house in 2012 this was not available - otherwise I would have put in a panel with two meters and a garage sub-panel for EV charging. Instead I put one meter so that my solar could offset my EV charging. See the PDF below. However, I have not yet heard of someone using aggregation with an EV-B meter.

NEMA Slides PDF

My Spreadsheet for PG&E rate comparison

 

[ken830]

You should start with the historical usage for your home, based on PG&E Green Button data. I have never added in hourly solar data, but that would be an interesting exercise. In my experience, E-1 is never the best choice, but I've never studied a home that uses a lot of A/C in someplace like Tracy or Chico. However, that's not your situation if we're talking about San Carlos.

You should also talk to PG&E about Net Meter Aggregation if you really want to optimize your setup. This is a new system that was started in 2014 that allows a NEM generator to allocate that generation across multiple meters. When I built my house in 2012 this was not available - otherwise I would have put in a panel with two meters and a garage sub-panel for EV charging. Instead I put one meter so that my solar could offset my EV charging. See the PDF below. However, I have not yet heard of someone using aggregation with an EV-B meter.

NEMA Slides PDF

My Spreadsheet for PG&E rate comparison

Wow! Load Aggregation did not exist when I first looked into solar back in early 2013, and I have never come across this since. Even after consulting with every solar-installer willing to talk to me, not a single person has ever mentioned this -- Not surprising, since not a single person has ever even dealt with anyone with two meters before, and had no clue how to properly size a system to minimize ROI.

I will start to look into this right away! Thanks!

 

[miimura]

A lot of solar installers don't even know how to run numbers with EV-A rates. I would not expect them to know anything about NEM Aggregation, even though they probably should.

 

[DCGOO]

Boy those rates are awful! Here the base rate (everybody pays) is .044/kWh, 24/7 after you go over 375 in the month. There is a TOU rate available that reduces it to .02 off peak (.12 peak). But it requires a separate drop and new meter. Not compelling for me to go there right now.

 

[Tedkidd]

Boy those rates are awful! Here the base rate (everybody pays) is .044/kWh, 24/7 after you go over 375 in the month. There is a TOU rate available that reduces it to .02 off peak (.12 peak). But it requires a separate drop and new meter. Not compelling for me to go there right now.

Upstate NY tou is equally uninspiring.

 

[thimel]

I agree with everyone telling you to go the EVA route if you are a large net consumer and otherwise have to pay the higher tiers.
Let me add, that there is NO reason to NOT charge the car every night. There is no need to run down the battery except perhaps very occasionally to let the battery management system track the battery capacity.

 

[ken830]

A lot of solar installers don't even know how to run numbers with EV-A rates. I would not expect them to know anything about NEM Aggregation, even though they probably should.

Definitely true. Every installer I talk to, I tell them... "You guys will get a whole lot more customers if you knew how to run the numbers." They only know how to size the system for 100% usage or some sort of tier-shaving for E1. Real shame. They have no clue on TOU, multi-meter, or EV-A/EV-B rates..

 

[miimura]

It's not quite that bad. All three installers I talked to in 2012 knew how to get to a $0 True-Up on E-6 given current usage. My problem was that I was getting a system for new construction so I didn't have historical usage to base the system sizing on.