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What a battery actually does

Solar alone shuts off in an outage. A battery is what keeps something running — but not everything.

Written by Brian Tilford, NABCEP certified.

Start here: why the lights still go out

What a grid-tied array does the moment the utility drops, what a battery changes, and how far a battery gets you before the sun comes back. The comparison below sets it against a standby generator.
Rather read it? What the video says, in words

Why a grid-tied array shuts down the moment the utility does, and what changes when a battery is added: the chosen circuits it carries, a switchover fast enough to miss, and a runtime measured in hours rather than days unless the sun comes back. The film then sets the battery against a standby generator — silent and finite against loud, fuelled and long-running — and shows that the sizing question is which circuits matter to you, not how big the house is.

What stays on

What a home battery keeps running in an outageA battery is sized around chosen circuits: the well pump, heat, refrigeration, lights and internet. Large loads such as air conditioning, an electric dryer or a range are usually left off the backed-up panel.Backed upThe circuits you chooseWell pumpHeatRefrigerationLightsInternetUsually notBig loads that drain it in minutesAir conditioningElectric dryerRangeHot tubWhole-home backup is possible, and costs more.
A battery is sized around chosen circuits, not the whole house. We design backup around what you actually care about losing — and say plainly what is not on the list.

Battery or generator

Home battery

Silent, automatic, finite

  • Switches over in milliseconds — you may not notice.
  • No fuel, no servicing, nothing to start.
  • Recharges from the roof during the day.
  • Runtime is hours, not days, unless the sun is out.

Standby generator

Loud, fuelled, long-running

  • Runs for days while fuel lasts.
  • Carries big loads a battery will not.
  • Needs fuel, servicing and an annual test.
  • Takes seconds to start, so the lights do blink.

Read next

How to check a solar proposalOne short film, nine questions, and a calculator that works on anyone's quote — including ours.What happens after you signInstalled and switched on are different days. Here is the gap, and why it exists.How the money actually worksWho owns the system, what is inside the price, and where the dealer fee hides.
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When you are ready to compare a real number

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