Charging: Reported consumption vs. meter reading

[Travis Denardo]

I've noticed something interesting over the past couple of months. When I took delivery of my Model S85 I had a 14-50 outlet installed in the garage.Within a month, I had my power company, Dominion Power here in Northern Virginia, install a second meter to take advantage of the EV off-peak charging rates. The line to the garage is run from the breaker panel, through the new meter, then to the garage (all done by an electrician, a family friend). The installation looks good and I monitored the whole thing (with intermediate knowledge of electricity).

Upon monitoring my charging and the number of kWh reported on my Dominion bill, they seem to differ significantly. I typically drive on average 450 miles per week, making the number of kWh actually used by the car to be upwards of ~200kWh very roughly. On my last few bills (the only ones with the EV rate), they are only charging me for ~51kWh on the EV Schedule. My other Schedule 1 meter reading seems to be on par with previous years (based on month).

When monitoring the charge on my MS, it shows ~230V @ 40A every charge, and it usually charges for a couple of hours when I've driven that day (last night was 3:53hrs with 116miles of range added). I even use VisibleTesla to monitor charging with it's graphing feature. It's consistent every charge. (I don't have a meter on the charge cable, but am considering it)

Is Dominion power not charging me properly, or is the meter not picking it up correctly? I called them to ask and they really had no clue and told me to check my internal wiring.

Anyone in Northern VA with DOM power seen anything similar? Any other thoughts?

 

[ran349]

You should check your new meter at night before you charge and then the next morning to see how much energy was used according to the meter. Then compare that to what the car used for charging. Based on your numbers, the car uses about 310 Wh of charge per rated mile, or about 31 kWh per 100 rated miles. Your meter should match this fairly closely. I suspect that it will. If that is true, then they should be charging you for that amount of energy. That should be a simple thing to resolve with the utility company once you know the meter is recording properly.

 

[richardw0000]

This may not be your case, but our utility will sometimes estimate the usage (and not read the meter) and bill us for the month based on the estimate. It will correct itself the next time they actually read the meter. Again, it may not be what is happening in your case, but a possibility.

 

[Boatguy]

I'm in California with a similar setup. Pacific Gas & Electric billed me reliably for the first six months, then nothing on the EV meter for about 3 months (house meter continued). Usage is visible on their web site and the usage data just stopped. Then a few days ago, they sent me a "catch up" bill for the missing three months, and all the data is online.

450/wk * 4 weeks ~ 1,800mi / month * 310Wh / mi ~ 560kWh / month.

Give them a couple of months, check online data if available, my guess is they'll get it sorted out. Utility companies are not the most competently run companies in the country.

 

[Travis Denardo]

Thanks for the comments so far, very helpful!

I did a little more research as you suggested. First, I took two pictures and verified the readings on the meters. 2277kWh on the EV meter, and 7373kWh on the whole house meter. They started at 000000 on or about 3/29/16. If I've only been charged for ~50kWh on the EV every month, they are missing a lot there.

Also, I was able to download my per 30 min breakdown of charges on the EV meter in a spreadsheet (PDF attached). So it seems like they are missing something, and the time on their meter is off, because off peak rates should start at 1AM, and I start charging at 1:05am every night I charge.

I hope they don't decide to have a "catchup" bill if they figure it out. A Dominion power work comes to the house every month around the 6th to manually read the meter with a handheld device. They said this type of meter doesn't have the Cellular or Radio Transmitter like the other standard meters they have.

 

[ran349]

Thanks for the comments so far, very helpful!

I did a little more research as you suggested. First, I took two pictures and verified the readings on the meters. 2277kWh on the EV meter, and 7373kWh on the whole house meter. They started at 000000 on or about 3/29/16. If I've only been charged for ~50kWh on the EV every month, they are missing a lot there.

Also, I was able to download my per 30 min breakdown of charges on the EV meter in a spreadsheet (PDF attached). So it seems like they are missing something, and the time on their meter is off, because off peak rates should start at 1AM, and I start charging at 1:05am every night I charge.

I hope they don't decide to have a "catchup" bill if they figure it out. A Dominion power work comes to the house every month around the 6th to manually read the meter with a handheld device. They said this type of meter doesn't have the Cellular or Radio Transmitter like the other standard meters they have.

It almost looks like they have a decimal point off in that spreadsheet. You should be charging at about 10 kWh per hour, not 1.0, as the spreadsheet shows. I would be surprised if they don't catch on to that pretty quickly, and you get a hefty catch up bill. But you can always hope.