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What Happens When the [Solar] Power Goes Out?

When you get some or all of your power from solar panels on your roof, what happens when a big storm rolls through and knocks out the power?

When the power goes out, grid-tied PV systems shut off as well, but not because they can’t produce electricity. The systems are programed to turn off automatically for safety reasons. When the power goes out, electricity for those sections of the grid are shut off so that workers can try to fix the issue. If PV systems stay on, and continue to send electricity through the wires while they are being repaired, you run the risk of electrocuting the workers.

The automatic shut-off is located in the inverter. The inverter (to find out more about how PV panels work, check out our Solar Power 101 page), usually located next to your meter, turns DC electricity into AC current so that it can be used by the home. The inverter is also the primary component of net-metering. When the power to the grid is shut off, the inverter recognizes that it can no longer receive electricity from the grid, and stops turning DC electricity into AC current. In other words, while the actual molecular process of converting solar energy into DC current cannot be turned off, the inverted can turn off your PV system’s ability to produce usable electricity.

In the earlier days of solar energy, this meant absolutely no power could be supplied to your home in the case of a power outage. With improving technology, inverters are now being released that can power some of the appliances in the home. These inverters have an external socket into which you can plug up to 1500 watts*. While the inverter is disconnected from the grid, it pulls power directly from the PV system. Due to the nature of solar energy, a stable power supply cannot be guaranteed. If the amount of sunlight hitting the panels fluctuates (due to clouds, debris, etc.) so will the power.

If one of your reasons for getting a PV system was the thought that you would be able to keep your entire home running in the event of a power outage, you may want to consider making an additional investment in a backup generator or a battery backup system. While the upside to a backup power system is obvious, there are downsides as well:

1. They are expensive. Generators strong and large enough to power a home can cost several thousand dollars. Batteries are also very expensive, and they take up a lot of space. The money spent on purchasing a backup power system negates almost all of the money you would have saved investing in a PV system in the first place.

2. They are generally unnecessary. Think about how many times the power has gone out in the past year. Maybe once or twice, right? Now assume that the power went out that many times every year and consider how many years it would take for you to get your money’s worth out of a backup system. This number may be different for everyone, but for most people it will take too many years for the system’s utility to make up for its cost.

3. They are vulnerable. If an event does occur where a backup system would be needed for multiple days, consider what type of event that may be: a flood, a severe snow storm, a hurricane etc. Your backup system may not be durable enough to withstand these events. If it is damaged and rendered unusable, your money would have been better spent on flashlights and candlesticks.

Fortunately, the power does not go off that often so there is no need to worry about this scenario any more than you did when you were getting your electricity from the grid.

*Number may vary by inverter model and producer