EV Customer (on TOU) Already Has or Adding Solar

If you already have an EV on a separate TOU meter, and you plan to install solar panels, the following 4 options (1a, 1b, 2a, 2b) are available to you.  After reviewing these options, you are welcome to contact CMLP at Lscott@concordma.gov or 978-318-3102 for a customized cost benefit analysis.

Whichever option you choose, CMLP strongly suggests that you join our peak demand reduction Google group, which will allow us to send you an email when peak demand is predicted. Thirty percent of your electric bill is directly related to the amount of electricity Concord uses for just one hour during the entire year. That one hour, the peak demand hour, occurs on a hot weekday afternoon during the summer months, typically between the hours of 2PM – 6PM. When you refrain from charging your EV during peak hours, everyone benefits with lower electric rates, since there are higher costs associated with the peaker power plants that produce electricity to meet the extra demand.

Option 1. Continue to Charge your EV on the TOU Rate 

If your EV meter is located on the load side (house side) of your house meter and you plan to add solar panels, you must relocate the meter to the line side (street side) of your house meter. The move is necessary because the meters currently used by CMLP do not have the technological capability to track both the time that power is being used (off-peak vs. on-peak) and where the power comes from (the grid vs. your solar panels and/or your battery). Because the meter cannot discern these parameters simultaneously, CMLP may end up charging you for electricity used by your vehicle that was actually produced by your panels.

Hiring an electrician to wire your EV meter to the line side of your house meter can cost from hundreds to thousands of dollars. Although you would need to pay your electrician for their labor and materials, CMLP will plug the EV meter into your new meter socket at no cost. CMLP’s electrician, Marty Boermeester (978-318-3141), is available to meet your electrician at your home before or during the job to discuss the best placement of the meter socket and answer questions. (See meter socket wiring diagrams for 200 amp and 320 amp systems here)

After relocating your EV TOU meter from the house side to the line side, you have 2 options:

  • 1a) EV always on TOU, House and Solar on R-1

When the TOU meter is wired to the line side of your house meter, only electricity delivered by CMLP will charge your EV. Electricity generated by your solar panels will power your house, but not your EV. Your EV can remain on the TOU Rate while your house and solar panels will be on the regular Residential Rate with net metering.


  • 1b) Opt out of the TOU Rate during high solar production

Installing a transfer switch between your house panel and your EV panel allows you to work around the technological limitations of our meters. During months when your panels produce more power than your house uses, you can flip the switch to disable the EV meter. This will allow your EV to be powered by your solar panels when there is sufficient solar production to meet both your house and EV needs.  When there is insufficient solar production to meet both your house and EV needs, EV charging will be billed at the regular Residential Rate with net metering.

The transfer switch will likely add hundreds of additional dollars to the cost of wiring your EV meter to the line side of your house meter. (See meter socket wiring diagrams for 200 amp and 320 amp systems here)

Option 2. Opt out of the TOU Rate permanently 

At no cost, CMLP can remove the second meter measuring usage for EV charging on- and off-peak. Off-peak EV charging at a lower rate than the standard Residential Rate will no longer be available under this option. Solar electricity produced by your panels will feed your car as well as your home.

With this option, you can choose one of these 2 alternatives:

  • 2a) Charge at the time of day that maximizes use of your solar electricity

This option gives you the flexibility to charge your car at any time of day. There are no bill credits or discounted rates associated with this option.


This option credits your electric bill $5-10 / month for programming your car to charge exclusively off-peak. These off-peak hours are 10 PM to 12 noon, Monday through Friday and all weekend (minor exceptions are allowed in case of emergency). This means that your solar panels can charge your car until 12 noon each weekday and all weekend.