Solar Industry News

What Happens With Unused Solar Power? Net Metering Explained

Unused power from this solar electric array will be automatically exported to the electric grid, earning the homeowner a credit against future electric use on non-sunny days.

One of the questions we get a lot is "what happens with unused solar power?"

The vast majority of the solar photovoltaic systems we install are grid-tied with no on-site storage, though, battery backup solutions are increasingly affordable.

A grid-tied system optimizes a solar array so that it will produce the most solar power it possibly can, under all circumstances. The system is tied into your home's electric panel, and the first priority for any solar power is to be used by your home's electric loads: fridge, well pump, water or space heating, electronics, etc.

If you produce more solar power than you use (as will be the case for many customers during daytime hours, especially in summer) then your system will feed power out to the grid. This essentially treats the grid like a battery, "feeding" the grid with clean solar energy that reduces the load on the local electricity grid, which saves everyone money. When this happens, your unused solar power becomes bill credits with your utility company which you can use when it's not sunny.

How does it work?

For a net-metered solar powered home, the electricity meter will run backwards to provide a credit against what electricity is consumed at night or other periods when the home's electricity use exceeds the system's output. Customers are only billed for their "net" energy use.

Exact details vary state-by-state, but generally, you get a 1:1 credit under net metering. Every 1 kilowatt-hour of electricity you send into the grid, you get 1 kilowatt-hour of bill credit which will reduce your remaining power bill. Extra bill credits (like you will get in the summer) can be banked for use in less sunny times of the year, like in the winter.

Year-Round Benefits 

Net metering allows customers to generate their own electricity cleanly and efficiently, and benefit from any unused solar generated energy. During the day, most solar customers produce more electricity than they consume; net metering allows them to export that power to the grid and reduce their future electric bills. 

The graph below is an example of SolarEdge Monitoring for a system's production on a great solar day. Your home uses energy from the grid exactly as it does now (in red), when the sun strikes your panels you produce your own power and self-consume it directly (in blue). In the middle part of a day you will typically be producing more power than you need, the excess (in green) automatically flows back into the grid and powers your neighbors homes. You receive credits for every kWh you send into the grid to cover the red and you can bank credits all summer to cover you through the winter!

production graph.png