What do you mean that I will have no power from my solar if the grid goes down???
This is likely one of the most mystifying quirks that interested property owners learn about solar when reviewing the possibilities.
Yes, solar, without battery backup, is immediately disconnected from your property’s electrical panel and, more importantly, the utility grid. This is because excess solar power would flow into the grid, energizing it, with the potential to electrocute any utility linemen who may be working to restore power.
With additional equipment, the entire property can be isolated from the grid and the solar array will continue to supply electricity to the main panel. Excess power generated will flow to the ground rather than the utility grid.
Once the electricity supplied by solar is no longer able to meet the demand at the main panel, the entire electrical system will be shut down. To avoid this from happening the property owner has two options.
The first is to manually turn the breakers off any circuit which is not deemed essential. The other is to install a critical loads subpanel and relocate those breakers for circuits deemed essential. The solar will only power this subpanel during a grid outage when sufficient solar electricity is being generated.
Practically speaking, the solar system will likely only be able to power those critical loads for 6 to 10 hours per day. This will be dependent on the season and critical loads selected. So even with the additional investment in equipment, a property would be without power for 14 to 18 hours each day during an extended grid outage.
Enter battery storage. This will resolve several of the shortfalls noted above. Firstly, all excess solar electricity generated during the day during a grid outage will be stored in a battery for use overnight. Properly matching the critical loads circuits to the solar and battery specifications will allow 24-hour-per-day electricity to these circuits for days or even weeks during a major grid outage.
Where the air conditioning use is high and continues through the night, it can be very expensive, if even possible, to provide all of a property’s power needs during an outage. Utility companies limit the size of solar systems which can be installed. This is usually 125% of the average annual consumption.
Most property owners choose a solar system that meets 100% of their annual needs as this generally yields the best return on their investment. During the peak cooling months of June through September, solar is not likely to produce enough excess power to store enough in batteries to keep everything running through the night.
An excellent option is to install a small, high-efficiency, ductless solar air conditioner to cool one or more smaller spaces to hunker down in the event of an extended outage. This leaves sufficient power for other essentials like refrigerator, freezer, lights, internet, smartphone charger and microwave.
Locate the solar air conditioner so that it also becomes the first AC unit used when the grid is operating normally. This will save on electricity consumption throughout the cooling season. Making this investment at the same time as solar and batteries will allow both to be smaller and hence priced lower, reducing the out-of-pocket cost of the new AC unit.
A portion of the excess electricity stored in batteries can be used to reduce or eliminate utility consumption during on-peak power periods when the solar system can no longer meet these demands late in the day. This provides further investment returns on storage batteries, even when is no power outage.
Well, there you go, some food for thought as to your options for having solar provide emergency power in the event of a grid outage. There is no one direction that gives the best result since that will be dependent on many factors about the property, consumption and needs.
As always, it starts with a review by a knowledgeable solar professional, who can lead the property owner through to the right decision for their situation and budget. Let’s get started!