Generator vs battery backup, by the numbers

A home battery stores electricity and gives it back when the grid drops. It has no engine, no fuel and no exhaust, so it is quiet and safe to place close to the house. It can recharge from the grid or from solar panels. What it cannot do is make new energy on its own. When it is empty, it waits for the grid or the sun.

Two common products show the range:

• Tesla Powerwall 3: 13.5 kWh of AC nominal energy, 11.5 kW maximum continuous output, 5 kW maximum continuous charging, and a motor-start rating of 185 locked-rotor amps, per Tesla's 2024 datasheet. Up to four units can be combined, and it accepts up to 20 kW of DC solar input.
• Enphase IQ Battery 5P: 5.0 kWh of usable capacity, 3.84 kVA continuous output, 7.68 kVA peak for 3 seconds, and up to 48 amps of locked-rotor motor start, per the Enphase datasheet. Units are typically combined for more capacity.

Two numbers decide what a battery can do in an outage. Energy, in kWh, sets how long it lasts. Power, in kW, and the motor-start rating set what it can run at once, including whether it can start an air conditioner compressor.

A standby generator is the opposite kind of tool. It holds no energy of its own, but it makes power for as long as fuel arrives. A 26 kW Generac burns 2.06 gallons of propane an hour at half load, or 188 cubic feet of natural gas. Its endurance is set by the fuel supply, not by a fixed store.

The rest of this page puts the two side by side using datasheet numbers, so the choice rests on arithmetic rather than marketing.

List what must run before comparing any battery or generator

Start with the smallest useful load: a refrigerator and an oxygen concentrator.

• A refrigerator draws about 750 watts running, per DTE Energy's appliance guide.
• A common home concentrator, the Philips EverFlo, averages about 350 watts.
• Together that is about 1.1 kW.

At that load, with no solar recharge:

• One Powerwall 3 (13.5 kWh) lasts about 12.3 hours.
• One Enphase IQ Battery 5P (5.0 kWh) lasts about 4.5 hours.

Adding units multiplies those hours. A real home also uses some lights, a fan, phone chargers and internet equipment, which shorten them.

Twelve hours is genuinely useful. It covers most everyday outages, which EIA data puts at about 65 to 80 minutes a year in Florida outside major storms. It covers an overnight outage after an afternoon thunderstorm. It does it silently, with no fuel and no fumes, which is why batteries are popular.

Now set it next to the local storm record. Milton's outages took about four days to clear in Sumter, Lake and Marion counties, roughly 96 hours. Irma's statewide outages took ten days to fall below 1 percent. Even at an essentials-only load, one battery covers the first night of a four-day outage, not the outage.

Refrigerated medicine adds weight to the gap. Ready.gov says to discard refrigerated medicine after an outage of more than a day unless the label says otherwise, and the FDA says a closed refrigerator keeps food cold about 4 hours. If the battery runs out on the first night, those clocks start. For medical households, see backup power for medical equipment.

Work out your own essentials load in watts before you shop

In a Florida September, most households want cooling, and the CDC advises older adults to rely on air conditioning rather than fans in very hot weather. That changes the battery math sharply.

Goodman's spec sheet lists a 3-ton heat pump at 13.4 running amps, about 3.2 kVA at 240 volts, and 83.3 locked-rotor amps at start. Add the 1.1 kW of essentials and the house draws about 4.3 kW.

• One Powerwall 3 can start that compressor, since its 185 locked-rotor amp rating is well above 83.3, and it lasts about 3.1 hours at 4.3 kW.
• One Enphase IQ Battery 5P cannot start this compressor, since its motor-start rating is up to 48 amps against 83.3, and 4.3 kW is above its 3.84 kVA continuous rating. Several units together would be needed.

Three hours of cooling is a long afternoon nap, not a night. A larger home with two systems, or a 5-ton unit at about 5.7 kVA running, drains a battery faster still. Stacking batteries helps, up to four Powerwall 3 units per Tesla's datasheet, but the cost rises with each one, and the stack still has a fixed store of energy.

For comparison, a 26 kW standby generator at half load is producing about 13 kW, enough for central air plus the kitchen and essentials. That load is already above one Powerwall 3's 11.5 kW continuous rating; even at 11.5 kW, one Powerwall 3 would last about 1.2 hours. The same generator runs about 47 hours on a full 120-gallon propane tank, 4.0 days on a 250 and 8.1 days on a 500 where a buried tank that size fits the lot, and indefinitely on natural gas while supply holds.

The details of sizing for cooling, including load management and soft starts, are on keeping the AC running.

Ask any battery quote for runtime with your AC running

The fairest way to compare is by outage length.

Short outages, minutes to a night. A battery shines. It switches over silently, needs no fuel and no maintenance during the outage, and creates no exhaust. Outside major storms, Florida customers average about 65 to 80 minutes of outages a year, per EIA. A battery handles nearly all of them for essentials, and a well-sized battery system can carry cooling for a few hours.

Storm outages, days. A fueled generator wins. Milton and Ian each took about four days to clear locally; Irma's statewide outages took ten days to fall below 1 percent. A battery cannot refill itself without the grid or the sun, and the days after a hurricane are not reliably sunny. A generator keeps running as long as fuel arrives.

Fuel is still the plan behind the generator. The district ARC manuals in The Villages cap an above-ground propane tank at 120 gallons, which runs a 26 kW unit about 1.9 days at half load. A generator on that tank needs a refill plan, a larger buried tank where the lot allows, load management or natural gas to cover a four-day outage. Natural gas, where a main reaches the home, avoids the tank limit; Peoples Gas says fewer than 1 percent of its customers had a gas interruption in the 2024 storms, by its own count. See generator fuel runtime and natural gas in The Villages.

So the question is not which technology is better. It is which outage you are planning for. A household that wants silence through evening blips and does not rely on cooling for health may be well served by a battery. A household that wants to keep running through a storm week usually needs fuel.

Decide which outage length you are really planning for

Many homeowners end up asking for both, and the combination can make sense.

In a hybrid setup, a battery carries the short outages silently, and a standby generator takes over when an outage runs long or the battery drains. With solar panels, the battery can also refill on sunny days, and the Powerwall 3 accepts up to 20 kW of DC solar input. The generator becomes the backstop rather than the first responder, so it may run less in a long outage, saving fuel and oil.

A few honest points about hybrids:

• Cost. Two systems cost more than one. A hybrid is a comfort and resilience choice, not a savings plan.
• Integration. Batteries, solar and generators have to be wired and controlled so they work together safely. Ask whether the specific models you are considering are designed to work with each other, and who supports the combination.
• Approvals. The district ARC manuals require architectural approval for exterior modifications, and they include a specific section on permanently affixed generators. Solar panels and exterior battery equipment are exterior changes too. Each piece also needs the right permit. Your installer confirms what applies to your district and address.
• Solar is not a storm guarantee. Cloud cover and storm damage can limit recharging in the days after a hurricane. Plan the generator's fuel as if the sun will not help.

A simpler hybrid is common too: a standby generator for the house, plus small battery packs or power banks for phones and a medical device's own battery, kept charged for the generator's daily oil-check pause. The CDC's Prepare Your Health guidance suggests car chargers and power banks as part of any backup plan.

The sizing guide helps you see what the generator side should carry.

Ask your installer whether a hybrid fits your home and budget

Here is a short guide, based on the datasheet numbers above.

A battery alone may suit you if:

• Your main concern is everyday outages, which EIA data shows are short in Florida outside major storms.
• You can live without central air for a day or more, or you are willing to buy enough battery capacity to run it for a few hours.
• You value silence and no fuel above multi-day endurance.
• You plan to leave for a relative's home or a hotel if a storm outage runs long.

A standby generator likely suits you if:

• You want to stay home through a multi-day storm outage, like Milton's four days locally.
• Someone in the home relies on cooling for health, or on an oxygen concentrator. SECO Energy does not prioritize medically necessary accounts during named-storm restoration.
• You have natural gas at the street, or you can plan propane refills.
• You want the house to keep running without anyone needing to manage it beyond a daily oil check.

Both may suit you if you want silent coverage for short outages and endurance for long ones, and the budget allows.

Whichever way you lean, ask for runtime in hours at your real loads, with and without the air conditioning. Any honest quote can give you that number. Compare the other options on portable vs standby, and read the full household plan on long-term power outage preparedness.

One request matches you with a licensed local installer for a free in-home estimate. Ask them to show you the runtime math for your home, and to tell you plainly if a smaller option would do.

Request a free estimate with runtime shown in hours