What a battery actually does when the power goes out

Start with the part that surprises people who already own solar: your panels do not keep your house running in an outage. Not at noon, not in June, not if the array is twice the size it needs to be.

A grid tied system is defined in Nevada law as one that operates in parallel with the utility's transmission and distribution facilities. Parallel is the operative word. When the grid stops, the system stops with it, and this is deliberate rather than a fault. A system that kept pushing power onto the wires during an outage could energise lines that utility crews have every reason to believe are dead.

So the honest framing is this. Solar is a bill product. A battery is what turns some of it into an outage product, and only for the parts you paid to back up.

"Whole home backup" usually is not

This is the phrase that causes the most disappointment, so it is worth being blunt about.

The common arrangement is a backup subpanel. Before installation, chosen circuits are moved onto it: typically the refrigerator, some lighting, a set of outlets, the internet equipment, sometimes one air conditioning unit. When the grid drops, those circuits keep running from the battery. Everything still on the main panel goes dark.

True whole home backup exists, and it costs more, because it has to carry every load in the house at once including the surge when a large air conditioner starts.

Ask any quote which of those two it is, and ask for the circuit list in writing. That list is the actual product you are buying, and changing it afterwards means an electrician back in your panel.

How long it lasts, and why nobody can tell you in hours

The honest answer is that it depends on what you put on the list, and in a Las Vegas summer one load dominates everything else.

Cooling is the whole argument. Lights, a refrigerator, phone chargers and a router are small and steady. An air conditioner is neither. Put cooling on the backup list and the battery empties in a fraction of the time it would otherwise last; leave it off and you have a comfortable amount of light, a working fridge and an unbearable house in August.

That is the real trade, and it is better faced at the quoting stage than at 4 pm in an outage. A number of hours quoted without knowing your loads is a guess wearing a decimal point.

There is one design question that changes the answer more than battery size does: can the panels recharge the battery while the grid is down? A system built that way runs the backed up loads from the sun during the day and refills the battery for the night, which is the difference between a few hours and riding out a long outage. Not every installation is wired for it. Ask.

The case for a battery is usually not the outage

For most Las Vegas households, outage protection on its own is a hard purchase to justify on arithmetic. The stronger case is that the same battery does a second job every ordinary day.

On NV Energy's optional residential time of use plan, summer on peak power between 6:01 pm and 9 pm costs $0.47155 per kilowatt hour, against $0.07305 off peak, on the schedule effective July 1 2026. A battery charged when power is cheap, or from your own roof, and discharged through that window is working every single summer evening, not only on the rare day the grid fails.

Why a battery pays for itself between 6 and 9 pm does that arithmetic properly.

There is a third thing a battery is often sold as doing, and it is worth being careful. From January 1 2027, southern Nevada bills gain a daily demand charge priced on the highest 15 minutes of use in a day, and it is scheduled for January 1 2027, under appeal. A battery is the only device that genuinely shaves a 15 minute peak, but it does not remove the charge, and there is a cheaper device that sometimes does enough. Can a battery get you out of the demand charge? and before you buy a battery, can a load controller do it cheaper? cover both.

What to ask before you sign

1. Backed up circuits or whole home? Get the circuit list in writing.
2. Does it recharge from the panels during an outage? Yes or no, in writing.
3. What happens to the air conditioning? Name the unit and say whether it is backed up.
4. How does it behave when the grid returns? It should reconnect on its own.
5. What is the warranty on the battery specifically, and what does it say about capacity after ten years?
6. Is any of this changing my net metering arrangement? Adding storage alone should not, but adding generation can. Net metering in Nevada explains why that distinction matters.

If you are on medical equipment

Say so before the quote, not after. Which circuits, which equipment, and how many hours it must run are design inputs that change the battery size, the circuit list and the recharge design. A standard backup arrangement is not built around that requirement and should never be assumed to meet it.

We size backup from your own panel and your own loads, and we will tell you plainly when a battery is not the right answer for what you want it to do.

We recheck this page quarterly. Last checked 2026-09-21. If a number here has moved, tell us and we will fix it the same week.