Oregon customers using a photovoltaic system have two meters measuring energy usage. It can be confusing to understand how energy is measured with these systems. We can help it make more sense.

The photovoltaic meter and the the net meter both have different purposes. The photovoltaic meter keeps track of how much energy is produced by your solar panels. The net meter keeps track of energy flowing to and from your utility provider.

Here are some examples of how this works:

Let's say your solar panels provide 200 kwh of energy. Here are three scenarios showing how energy is measured at the net meter:

• If you consumed 200 kwh in a given month, the photovoltaic meter would read 200 kwh and the net meter would read 0 kwh.
• If you consumed 100 kwh in a given month, the photovoltaic meter would read 200 kwh and the net meter would read -100 kwh (credit).
• If you consumed 500 kwh in a given month, the photovoltaic meter would read 200 kwh and the net meter would read 300 kwh usage from us.

These are simple examples that show how your photovoltaic meter could read 200 kwh, while your utility bill could read anywhere from a 100 kwh credit to 300 kwh usage - depending on your home's use. This is because the energy produced by your photovoltaic system provides the needs of your home first. Only after the home's energy needs are met does the excess energy flow to our system, which is stored for future use. This net metering approach allows your photovoltaic system to use us as your back up energy source.

The net meter 
Before your net meter is installed, it is tested to ensure it meets American National Starndards Institute (ANSI) requirements for meter accurace and performance. Then, to ensure proper operation, we install and maintain the meter.

The net meter keeps track of the flow of energy to and from the home. If more energy flows from our system to your home, the kwh's are billed at the current electric rate plus appropriate monthly charges. If more kwhs flow from your home's photovoltaic system to our system than you use from us, we credit your bill at a rate of 4.22 cents per kwh after application of appropriate monthly charges.

Energy efficiency and net metering
Your photovoltaic system works best when providing electricity to the most energy-efficient equipment available. For maximum efficiency, appliances should be Energy Star rated, lighting should be compact florescent, other equipment should be premium efficiency and heating/cooling equipment, insulation and glazing should meet or exceed current building code levels. For more about energy efficiency, click here.

For more information about photovoltaic solar panels, visit the  Energy Trust of Oregon.