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Are you planning on ever getting rooftop solar installed? If so, its best to have the car on the main house meter where you can offset with your panels I would think.
Are you currently on a TOU rate for your whole house? If you aren't, and those rates don't work for your whole house (because folks are home during the peak hours), then it makes sense to look at a separate meter so you can take advantage of lower kWh rates for nighttime charging.
If you already have your whole house on a TOU rate, I am not sure having the car on a separate meter is that beneficial.
Are you currently on a TOU rate for your whole house? If you aren't, and those rates don't work for your whole house (because folks are home during the peak hours), then it makes sense to look at a separate meter so you can take advantage of lower kWh rates for nighttime charging.
If you already have your whole house on a TOU rate, I am not sure having the car on a separate meter is that beneficial.
aesculus
Still Trying to Figure This All Out
If you ever run into Tier 3 or 4 then a separate meter would be helpful to keep your rates low.
The Calif IOU's run trials of sub meters (PG&E is currently closed but expect an new one in November). These allow for metering your EV just like a separate meter but without having to install another panel etc.
The Calif IOU's run trials of sub meters (PG&E is currently closed but expect an new one in November). These allow for metering your EV just like a separate meter but without having to install another panel etc.
eye.surgeon
Active Member
Fanatic1
Member
Fanatic1
Member
Borgholio
Member
I just finished doing a lot of spreadsheet work to figure out the answer to this for when my M3 arrives. Here's what it boils down to (and I'm on Southern California Edison so your local utilities might be different).
The EV-only rate requires a second meter. You can't get it on your main line. The EV-only rate is the lowest you can possibly get, 10 cents per kwh during off-peak hours. Getting the second meter is a good idea if you can't get a TOU (time of use) plan on your main line.
The TOU plan means you get charged more per kwh (even as high as 40 cents per kwh) during peak hours, but substantially less during off peak and "super" off peak hours (where you can get rates as low as 12 cents). The TOU plan works great if you don't typically have people at home during the day, so you don't use much of the high-rate power and you do all your electrical stuff (dishes, laundry, charging your car, using your central A/C, etc...) during the low-rate times of day. In the case of a Tesla, set it to begin charging at 10pm (when the 12 cent rate begins) and you can fill the battery with power that's only a tad more expensive than the EV-only rate. Plus, a TOU rate won't require the installation of a second meter and setting up a second service. That does cost you money out of pocket, whereas simply switching to a TOU plan does not.
Now if you have people home all day (stay at home spouse, work at home, kids at home during summer vacation, etc...) then the TOU is not a good idea since you'll have people using lights, A/C, television, and other stuff when rates are high. So in a case like this, using a standard 4-tier system is best since you won't be dinged for WHEN you use power, just by HOW MUCH you use. At this point you get a second meter that uses the EV-only rate so you can charge your car at night when you get cheap rates and you won't blow your usage into Tier 4 on the main meter. The downside is that you have to pay for the second meter...but it might be worth it if you would otherwise spend a lot of money on Tier 4 or Peak-rate power.
The EV-only rate requires a second meter. You can't get it on your main line. The EV-only rate is the lowest you can possibly get, 10 cents per kwh during off-peak hours. Getting the second meter is a good idea if you can't get a TOU (time of use) plan on your main line.
The TOU plan means you get charged more per kwh (even as high as 40 cents per kwh) during peak hours, but substantially less during off peak and "super" off peak hours (where you can get rates as low as 12 cents). The TOU plan works great if you don't typically have people at home during the day, so you don't use much of the high-rate power and you do all your electrical stuff (dishes, laundry, charging your car, using your central A/C, etc...) during the low-rate times of day. In the case of a Tesla, set it to begin charging at 10pm (when the 12 cent rate begins) and you can fill the battery with power that's only a tad more expensive than the EV-only rate. Plus, a TOU rate won't require the installation of a second meter and setting up a second service. That does cost you money out of pocket, whereas simply switching to a TOU plan does not.
Now if you have people home all day (stay at home spouse, work at home, kids at home during summer vacation, etc...) then the TOU is not a good idea since you'll have people using lights, A/C, television, and other stuff when rates are high. So in a case like this, using a standard 4-tier system is best since you won't be dinged for WHEN you use power, just by HOW MUCH you use. At this point you get a second meter that uses the EV-only rate so you can charge your car at night when you get cheap rates and you won't blow your usage into Tier 4 on the main meter. The downside is that you have to pay for the second meter...but it might be worth it if you would otherwise spend a lot of money on Tier 4 or Peak-rate power.
Fanatic1
Member
aesculus
Still Trying to Figure This All Out
The meter itself is like $75 dollars.
The other costs can be quite high. I think PG&E estimates $1-2k depending on your situation. Note that if you can do it yourself or with a friend and your charging station is adjacent to the new panel, you could probably do it for around $200 plus the cost of the HPWC. In my case PG&E wants me to install a gutter so both meters can be split at the secondaries.
aesculus
Still Trying to Figure This All Out
I did the math the other day on usage and various rate plans. I also contacted PG&E during an application for a second meter and they looked at my loads over the last several years. If I charged during peak times I could go over my panel load but it would have to be when my heat pumps and spa are all running at max with the heat strips on. So if I avoid charging during those times I should be OK. Planning on charging overnight except during emergency charges so none of that is working then.
So I decided not to get a second meter after all and am moving from my E7 TOU plan plus a EVB TOU second meter over to a single meter running on the EVA TOU plan that is not tiered. NEM still applies to the EVA plan so it might actually work out better if I can shove as much load as possible into off peak. Today with E7 we only have on and off peak but EVA has three periods so it will take some adjustment. And of course all of my programmable devices only have 4 daily times rather than the 8 I need for the extra periods but I can probably make it work OK.
So I decided not to get a second meter after all and am moving from my E7 TOU plan plus a EVB TOU second meter over to a single meter running on the EVA TOU plan that is not tiered. NEM still applies to the EVA plan so it might actually work out better if I can shove as much load as possible into off peak. Today with E7 we only have on and off peak but EVA has three periods so it will take some adjustment. And of course all of my programmable devices only have 4 daily times rather than the 8 I need for the extra periods but I can probably make it work OK.
