The storm hit. The power’s out. With all the damage around you, it looks like you might be without power for a few days (at least). But you planned for this. You have a home backup battery. What happens now?
If you’re considering a home backup battery, or you already have one and haven’t needed it yet, you might be wondering what you’re supposed to do when the inevitable happens. The good news is: you probably won’t have to do much at all.
Modern home batteries are paired with an automatic transfer switch. That’s a switch, usually installed near your home’s electrical panel, that allows you to go from grid power, to battery, and back. And, because it’s automatic, you don’t have to do anything at all.
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The instant the grid goes down, the automatic transfer switch recognizes the loss of power and automagically disconnects your house from the grid, seamlessly connecting it to your backup battery instead. Your lights stay on, the refrigerator keeps humming, and whatever else you’ve chosen to back up just keeps on keeping on. In some cases, the transition to battery power happens so smoothly that you might not even realize the neighborhood’s lost power, not noticing the neighbors’ dark windows until you step outside.
When the power comes back, that side of the switch gets energized, and it does its thing again, only in reverse – switching you back from battery to grid power and intelligently re-charging the battery in anticipation for the next blackout.
How long will my battery last?
13.5 kWh Powerwall battery; via Tesla.
Unfortunately, this is one of those questions that doesn’t have an easy answer. In the simplest terms, if you have a small battery and try to keep the AC running, you might run out of juice in a few hours. On the other hand, if you have great big battery and save its electrons for just the barest essentials (a few lights, a laptop, and a phone or radio, for example) you might never run out of power.
To put some numbers to that, a 31 cu. ft. Samsung RF32CG5400SRAA stainless steel refrigerator is rated at 785 kWh/year. That works out to about 2.15 kWh/day. Factor in 20-40% higher energy needs for warmer temperatures, a few daily door openings, defrost cycles, inverter losses, etc. and you’re looking at 18-22 kWh of usable battery capacity to keep that thing running for a full week on battery power. Now do that same math for every appliance you deem a “must have,” then do the “nice to haves,” and on down the line.
What you need to do, in other words, is talk to the experts. Let them know what appliances you need to keep running, how long you want to prepare for, and let them do the math to help determine which battery solution is right for you.
I’ve included a video that covers the process of picking a solar battery from EnergySage (a trusted affiliate partner), below, and invite you to share some of your own backup battery-picking experiences in the comments.
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