Standby generator vs. battery backup in Illinois

A battery also has to be enrolled in the utility's virtual power plant program to get the rebate, so the utility can draw on it at set summer peak times. See whole-home battery backup.

Usually not long. The U.S. Energy Information Administration lists Illinois among the states whose customers averaged less than one power interruption in 2024. ComEd reported Chicago customers averaged 28 minutes without power in 2025, and that more than 99% of customers affected by outages were restored within 48 hours.

• August 2020 derecho: more than 635,000 ComEd customers lost power, and about 200,000 were still out two days later.
• July 2023 storms: more than 225,000 Ameren Illinois customers were interrupted over three days.
• July 15, 2024 storms: more than 440,000 ComEd customers lost power after a line of storms and tornadoes; about 82,000 were still out two days later.

So the real question is how long your worst outage could last. A battery handles the typical short outage well; multi-day storm outages are where a generator, or a battery with enough solar to recharge, earns its keep.

On propane, a 500-gallon tank holds about 400 usable gallons because tanks are filled to 80%. At a half-load burn of about 2.53 gallons an hour, that's roughly 6.6 days of nonstop running, and deliveries can be slow after a big storm. Natural gas has no tank to run dry, so it is the usual choice where a gas line is available.

National fire code rules followed by generator makers require at least 5 feet between the generator and any window, door or vent, plus 5 feet of clearance above it. Many Illinois villages add their own rules: Lincolnwood, for example, allows generators only in rear yards and at least 20 feet from a neighbor's window, and Northbrook requires a plat of survey and an electrical permit.

Generators also need a gas line sized for full load, an automatic transfer switch, and regular care: Generac calls for an oil and filter change every 200 hours of running or at least every two years, and more often in extreme temperatures. They run a short self-test each week, at about 57 dB, quieter than the roughly 67 dB of full operation.

For most outages, yes. One 13.5 kWh battery can run the essentials for about a day, and solar panels can recharge it on sunny days, which can stretch backup indefinitely in summer. Whole-home backup with central air usually takes two or more batteries. Batteries can lose some output in very cold weather; Generac's PWRcell 2 spec sheet, for example, notes reduced output below 32°F.

Where a battery falls short is a long winter outage with heavy loads like electric heat. If that's your main worry, a generator, or both, makes more sense.

Yes. Some homes use the battery for short outages and everyday solar savings, with a generator as a last resort for long ones. They connect through a transfer switch and usually work as separate layers: Tesla notes, for example, that Powerwall doesn't recharge from a generator. Ask an installer to design both together so the switching is automatic.

Whatever you choose, never run a portable generator indoors or in a garage. The Consumer Product Safety Commission linked portable generators to an estimated 765 carbon monoxide deaths from 2009 through 2019.