Leave the lights onwhen the power is out.
If the power goes out, your home goes dark, even with a solar system on the roof. Having a battery is what changes things. Here’s how it works, and what it takes for your whole home to be backed up indefinitely.
The Blackout
Why Solar Panels Are Not Enough in an Outage
Every grid-tied solar energy system in Florida behaves the same way. The second the utility power drops, the inverter shuts the solar system down. It isn’t a defect, it’s a regulatory requirement to avoid electricity being pushed back into the same power lines that workers are repairing.
A battery changes the rule, because it changes the wiring. The battery recognizes the power outage and immediately isolates your home from the grid with a component called the transfer switch. Now your home is working independently: nothing you produce can reach the street, and your lights are allowed to stay on.
Sun, Battery, House
How the Three of Them Work Together
During an outage
The transfer to Home Backup Mode happens automatically and in well under a second: no generator to start, no cord to drag out, no fuel to find. Overnight the house runs on energy already stored in your battery. Come sunrise the panels start capturing energy, run the house, and pour the surplus into the battery for the next night.
On an ordinary day
Choose between keeping your batteries full at all times to be ready for an outage or using them as a buffer mechanism to squeeze out some extra savings by switching your utility rate from flat to off/on-peak hours.
How Many Batteries Do You Need?
There is no one-size-fits-all answer, because it depends less on the house and more on your needs. It comes down to two numbers:
Power output — kW
What can run at once.
Before thinking about how long your backup will last, the question we need to answer is which appliances you want to keep using. Different appliances need different power inputs to stay on, while batteries have a specific total power output capacity, so the goal is making sure the output is at least as big as the expected input.
Stored energy — kWh
How long it lasts.
Once we define what appliances you need, the next question is: how long do you need your backup to last? An example: A Powerwall 3 alone holds 13.5 kWh. A typical South Florida home with the AC running uses somewhere between 2 and 4 kWh an hour on a hot night. That means up to 7 hours before your backup runs out.
Let us help you understand what the right size is for you by comparing scenarios.