Can a Generator Run Your AC or Furnace? A West Michigan Guide

Since the storms knocked the power out this month, every third homeowner I talk to has asked me some version of the same question: should I buy a generator, and will it run my furnace or my air conditioning? Fair question. When Consumers Energy's outage map lights up orange from Grandville to Kentwood and your house is sitting at 85 degrees, a generator starts sounding less like a luxury and more like a basic appliance.

Let me be upfront about something first. Mazure's services heating and cooling equipment. We don't sell or install generators, and I'm not going to pretend we do. But I've spent my working life on the furnaces and air conditioners that people try to run on generator power, and I've seen it done right and done very wrong. This is buying advice from the HVAC side of the fence, so you size things correctly, connect them safely, and don't cook a $2,000 control board trying to save your groceries.

The short version: your furnace is easy to back up, your central AC is hard, and the connection method matters more than the generator itself.

What Your Heating and Cooling Equipment Actually Draws

Here's the part that surprises almost everyone. A gas furnace doesn't make heat with electricity. The gas does the heating; electricity just runs the blower motor, the inducer fan, the igniter, and the control board. A typical furnace draws somewhere between 400 and 800 watts while running, with a brief bump when the blower starts. A boiler is even lighter, since a circulator pump and controls might pull a couple hundred watts total.

That means the equipment that keeps your family alive in a January ice storm can run on a modest portable generator. A 3,500-watt unit has room to spare for the furnace plus the fridge and some lights. In West Michigan, where a winter outage is a genuine safety issue and not just an inconvenience, that's the backup that matters most.

Central air conditioning is a much tougher ask, and I'll get to why in a minute. First, some honest numbers:

Those are ballpark figures. Your equipment's nameplate and the compressor's locked rotor amps tell the real story, and they vary by model.

Why Central AC Is the Hard One

Look at that table again. A 3-ton AC runs on about 3,500 watts, which sounds manageable. So why do I keep seeing homeowners with 4,000-watt generators standing in their driveway wondering why the AC won't start?

The compressor. When a standard AC compressor starts, it doesn't ease into motion. It goes from dead stop to full speed in a fraction of a second, and during that fraction of a second it can pull four or five times its running wattage. The generator has to survive that surge, and most portables can't. The generator bogs, the voltage sags, the compressor stalls, and either a breaker trips or something gets hurt. Usually the something is your compressor or your generator, and neither is cheap.

There's a workaround, and it's a good one: a soft-start kit. It's a device installed on the condenser that ramps the compressor up over a second or so instead of slamming it to full speed. A quality soft start can cut the starting surge by more than half, sometimes down to a quarter of the original spike. That's the difference between needing a monster generator and getting the job done with a 7,500 to 9,500 watt portable. Soft starts have a side benefit too. That easier start is gentler on the compressor every single day, not just during outages, and it's one of the reasons a well-treated system lasts longer in Michigan.

Sizing this correctly means knowing your specific compressor's numbers, not guessing from the tonnage. Get those numbers before you buy the generator, not after.

Portable With a Transfer Switch vs. Whole-Home Standby

There are really two sane paths here, and the right one depends on your budget and how often you lose power.

Path one: a portable generator plus an interlock or transfer switch. A licensed electrician installs either a manual transfer switch or an interlock kit on your panel, which lets you safely feed selected circuits from a generator inlet on the outside of the house. In the 2026 Grand Rapids market, figure roughly $500 to $2,000 for that electrical work depending on your panel, plus $700 to $2,500 for a decent portable in the 6,500 to 9,500 watt range. Call it $1,500 to $4,500 all in, and you can run the furnace, the fridge, some lights, and, with a soft start on the AC or a smaller cooling option, stay reasonably comfortable.

Path two: a whole-home standby generator. Permanently installed, runs on natural gas or propane, starts itself within seconds of an outage, and carries most or all of the house including central air. Installed prices in our area run wide, honestly anywhere from about $10,000 to $20,000 or more depending on size, gas line work, and placement. It's real money. For the right household it's worth every dime, and I'll say who that is further down.

Either way, the electrical side is not a DIY project. A licensed electrician pulls the permit, sizes the inlet, and makes the connection legal and safe. I say that as a guy who's opened plenty of furnace cabinets and found scary wiring behind them.

The Other Way Generators Kill People

While I'm on safety: never run a portable generator in the garage. Not with the door open, not "just for a bit." Generators put out carbon monoxide fast, and CO doesn't care that you left a gap. It seeps into the house, it has no smell, and it kills whole families in their sleep. Run the generator outside, at least 20 feet from the house, exhaust pointed away from windows and doors, and make sure you've got working CO alarms on every floor. If a CO alarm ever goes off, get everyone out first and make your calls from the driveway.

We think about air in your house a lot around here, and CO is the deadly end of a spectrum we cover in our indoor air quality guide. If your CO alarms are more than seven years old, replace them this week. That's cheaper than any generator and matters more.

Cheap Power Can Wreck Expensive Equipment

Here's the part of this conversation I own as the HVAC guy. Modern furnaces and air conditioners aren't the simple machines your dad's were. Variable-speed ECM blower motors, inverter-driven compressors, and control boards full of electronics all expect clean, steady power at the right voltage.

An undersized or low-quality generator gives them the opposite. When the load gets close to the generator's limit, voltage sags. When cheap units run, the power can come out rough even when the voltage number looks fine. ECM motors and boards hate both. I've replaced boards after outages where the generator did more damage than the storm did. Two summers ago I was at a house in Hudsonville where a bargain generator had been proudly running the furnace blower all weekend. The ECM module was dead within the month. Nobody can prove it in court, but I know what I saw.

The fixes are simple. Size the generator so your real load sits around half to three-quarters of its rating, not pinned at the max. If your equipment has variable-speed anything, spend the extra on an inverter generator or a well-regarded conventional unit with tight voltage regulation. And put surge protection on the HVAC circuits regardless, because the grid coming back on is its own hazard. We covered that whole subject in protecting your HVAC from summer storms and power surges, and if your AC has been acting strange since the lights came back, start with our post on AC trouble after an outage.

What Actually Makes Sense for Most Families Here

After all that, here's my honest recommendation for a typical family in Jenison, Hudsonville, or Wyoming that loses power a couple times a year.

Skip trying to run central air on a generator at all. Get the portable-plus-interlock setup sized for the furnace, the fridge, the sump pump, some lights, and one small cooling load: a window unit in a bedroom, or one zone of a ductless mini-split if you have one. A mini-split is a sweetheart on generator power. The inverter compressor ramps up gently, so there's no brutal starting surge, and a single zone sips 600 to 1,500 watts while cooling the room you actually sleep in. If you've been curious about them anyway, our ductless mini-split page and this plain-English explainer cover how they work. One cool bedroom gets a family through a July outage just fine. Winter is the season that scares me more, and the furnace-on-a-portable setup handles it for cheap.

Whole-home standby earns its price in specific situations. Somebody in the house on oxygen or powered medical equipment. A home office where three dark days means real lost income. A well that quits with the power. Or a location that just gets hit, and folks in parts of Georgetown Township know exactly what I mean, where the outages come often enough that the generator runs several times a year instead of sitting as insurance. In those homes, automatic start and full-house coverage including the AC stops being a luxury.

Whichever way you go, have a licensed electrician do the connection, and feel free to have us look over the HVAC side. If you want a second opinion on whether your furnace, AC, or a future mini-split plays nice with the generator you're considering, reach out or schedule a visit and we'll give you straight numbers off your actual equipment.