Depending on where you live and which solar incentive programs you participate in, your utility (or your solar company) probably installed a meter on the side of your house, after your panels went up but before you turned on your solar energy system. They may have added a second meter, or replaced the one you had. As of this writing, the three main types of “solar meter” are:

  • Net meter
  • Bi-directional meter
  • Dual meter

People who get “Net Metering” from their utilities (the majority of solar owners today, although that is changing) have one of the first two types of meter, which replaces the original, traditional utility meter.

Solar owners in Rhode Island’s Renewable Energy Growth (REG) program keep their traditional utility meters, and have a second meter added to the house. This approach may eventually be used in Massachusetts, too, since an REG-type program is being developed to replace the SREC incentive program in 2018.

Here’s how each type of meter works, generally speaking:

Net Meters

solar system net meterNet meters show the net consumption of power in the household. A net meter does not tell you how much solar electricity you pushed out to the grid, or how much “regular electricity” you took in from the grid. It indicates the difference between the two, or the “net usage.” The cool thing is that your net meter actually runs backwards if you are producing more solar energy than you are using at that point in time.

The net meter has two displays or registers. The first register shows all 8s and simply means the meter is functioning properly. If something other than an 8 is shown, contact your electric company. The second register shows your net usage, and is what the electric company uses to determine how much you owe on your electric bill, or if you have generated a credit. If you used 100 kWh of energy but generated 60 of those with your solar system, the net meter will show 40.

Bi-directional Meters

solar system bi-directional meterBi-directional meters have three display screens. One is a test screen where all lights are on. The second shows power coming in from the grid, and the third shows power going out from your solar into the grid.

Typically, the screen notation with 001 shows power coming in, and 002 shows power going out. Other meters use DEL or DL, and REC or RC to indicate which way the electricity is flowing. Ask your electric company to explain your screens when they install your meter.

Dual Metering

solar system dual meteringIn a dual metering situation, you have two separate meters that do not communicate.

Your original utility meter continues to tell you how much electricity you are taking from the utility. This is your usage meter (shown on the right in this photo). A new, second meter measures how much solar electricity you send to the utility. This is called a production meter or a generation meter (and is shown on the left in this photo).

Both meters are tied to your electric company account.

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