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Switched to Eversource TOU Rates for my EV charging

David29

Supporting Member
Supporting Member
Aug 1, 2015
2,272
1,963
DEDHAM, MA
After learning a few months ago from this group that Eversource had Time of Use (TOU) rates available in Eastern MA, I applied to Eversource to switch to TOU for my EV charging service. I have a separate service for charging, so by charging at night I will have little or no usage during the peak daytime hours. The meter was (finally!) installed today. So I am looking forward to seeing a savings of roughly $10/month on my costs for EV charging.

It seemed to take an inordinately long time to switch my meter. To make a long story short, after a month's wait I made several phone calls. Finally I encountered a customer service person who acted proactively and was able to speak with the right person to expedite the request. As it was, it was nearly 7 weeks from request to installation.

What would be nice is if I could log into the Eversource website and see my usage. I know that the meter can deliver the data, and I know that some other utilities offer that service, but I can't find any indication of that on the Eversource web site.

Otherwise I will just have to take data off the meter and runs the numbers (if and when I want to).

The trick now will be to maximize the savings by minimizing the energy usage during peak periods. For me, the main risk will be preheating or precooling the car.

20161125_125021.jpg
 

tga

Supporting Member
Supporting Member
Apr 8, 2014
4,023
2,990
New Hampshire
FYI, that meter picture is enough info for someone to learn your name, service address, and billing address (provided they have access to the customer database).
 
  • Informative
Reactions: David29

Doug4650

Member
Jan 16, 2016
51
24
Somerville, MA
I took a look at the numbers, but couldn't make it pay off. For me my usage is low enough that the fixed monthly costs outweighed the lower rates on the non-peak usage. is your bill more than $100/month?
 

David29

Supporting Member
Supporting Member
Aug 1, 2015
2,272
1,963
DEDHAM, MA
I took a look at the numbers, but couldn't make it pay off. For me my usage is low enough that the fixed monthly costs outweighed the lower rates on the non-peak usage. is your bill more than $100/month?
When I ran the numbers, it looked as it I'd save about $10/month. But that is a concern. We'll see how it turns out. Committed for a year as you likely know.
Not sure of your situation, but mine is a separate circuit solely for EV charging, so essentially no peak usage should be needed. I hope!
 

David29

Supporting Member
Supporting Member
Aug 1, 2015
2,272
1,963
DEDHAM, MA
I ran some numbers again and it is true that the payoff is dependent upon how much usage you have. But I calculate the break-even point (with current winter rates) to be 97.5 miles, assuming 100% charging efficiency, all charging at off-peak times, and my average energy use of 326 wH/mi for my first year of owning the Model S.

The difference in rate per kwh is 11.2 cents. The difference in the monthly fee is $3.56. So it looks to me as if I need to use 31.8 kwh to offset the fee increase with the savings per kwh. For me, that 31.8 kwh is 97.5 miles as explained above.

In fact, of course, I will have probably have some peak period usage, so i will have to manage that. Since the peak period starts at 8 AM in winter, using the grid to preheat the car (or to melt off snow) will be costly (26.8 cents per kwh!).

Other factors are how much charging you do elsewhere than home (Superchargers or public level 2, etc.), what the wh/miles are, what the charging efficiency is (you buy more power than what actually gets into the battery), and how much other non-charging power is used on the charging circuit (in my case, some security lamps that only operate when they detect motion near the car).
 

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