Inverter Generator vs Conventional Generator for Home Backup

The lights flicker, the furnace goes quiet, and the house goes dark. Over the next hour you work out what matters most: the fridge, the sump pump, the furnace, and the Wi-Fi so the kids can reach Grandma. Choosing a generator comes down to that same list. An inverter generator is quieter, easier on fuel and safer for electronics. A conventional generator gives you far more watts for the money and usually has the 240-volt outlet a well pump or transfer switch needs. Here's how to tell which one fits your house before the first ice storm.

01The Short Answer

Inverter generators run quieter, burn less fuel at light loads and make cleaner, steadier power. Conventional generators give you a lot more watts per dollar.

Choose an inverter if your outage list is mostly the refrigerator, the furnace blower, the router, phone chargers and a laptop. A 2,200-watt-class inverter such as the Honda EU2200i typically sells for about $1,100–$1,300. It's light enough to carry, quiet enough to live with and easy on fuel when it's running just a fridge and a few small things.

Choose a conventional generator if you need 240 volts for a well pump, an electric water heater, or a transfer switch that feeds selected circuits in your panel, and you want that power at a low price. The Generac GP8000E is a good example. It's rated at 8,000 running watts, has a 120/240V locking outlet, and costs roughly $1,100–$1,200 at the time of writing.

Look at those two prices. For about the same money you get roughly 2,200 watts from one and 8,000 from the other. The rest of the decision comes down to what that difference means for your house.

02Power Quality and Why It Matters

Household power comes out as a smooth, even wave. Total harmonic distortion (THD) measures how far a generator's output strays from that clean wave. A low number means smooth power that looks like what the utility sends. A high number means rougher power with ripples and spikes in it.

Inverter generators first make raw AC power, then convert it to DC, then electronically rebuild it as clean AC. That's how they typically stay below about 3% THD. A conventional generator sends power straight from the alternator, and its THD usually runs somewhere around 9% to 30%, depending on the model and the load.

Here's what that means in your house:

• Laptops, TVs, routers and phone chargers are built around small circuit boards that do best on clean power. An inverter is the safer choice for them.
• Modern furnaces often have electronic control boards and variable-speed blower motors. Some furnace makers and HVAC techs recommend clean power for these, so if a generator will run your furnace this winter, an inverter or a low-THD conventional model is worth paying attention to.
• Medical equipment such as CPAP machines and oxygen concentrators deserves extra care. Ask the device maker what kind of backup power they approve, and treat an inverter as the starting point.

Plenty of newer conventional generators advertise low THD. If you're leaning conventional, check the spec sheet for that number.

03Noise and Fuel Use

The cleaner power and the quieter running come from the same design. A conventional generator's engine runs at a fixed speed whether it's powering one lamp or the whole kitchen. An inverter's engine speeds up and slows down with the load. With just the fridge running, it idles along. When the microwave comes on, it revs up.

That makes a big difference in noise. Inverters typically run around 48–65 dB(A), while conventional units run about 70–95 dB. A Consumer Reports engineer has said inverters are "generally quiet enough not to drown out nearby conversation." A conventional unit at the loud end of that range is something your neighbors will hear all night.

Some real numbers from the big Honda inverter, the EU7000iS: 58 dB(A) at full rated load and 52 dB(A) at quarter load.

Matching engine speed to the load also saves fuel, especially overnight when the house only needs a little power. Sellers often claim savings of 20–40%, but your results depend on how lightly you run it. Runtime figures show the difference more clearly:

• Honda EU7000iS (5.1-gallon tank): about 6.5 hours at rated load and about 16–18 hours at quarter load.
• Generac GP8000E (7.9-gallon tank): about 10–11 hours at half load.

Because of how far the Honda stretches at light load, one fill-up can carry an inverter through a whole night of fridge-and-furnace duty.

04Watts and Cost: Two Real Examples

To compare the two types fairly, put two large units side by side.

Honda EU7000iS (inverter) - 5,500 running watts, 7,000 maximum - About $4,899–$4,999 at the time of writing, plus freight, setup and tax - 5.1-gallon tank, about 6.5 hours at rated load and 16–18 hours at quarter load - About 261–263 lb dry - Two 20A 120V GFCI outlets, one 30A 120V locking outlet, and one 30A 120/240V locking outlet - 3-year residential warranty

Generac GP8000E (conventional) - 8,000 running watts, 10,000 starting - About $1,100–$1,200 at the time of writing - 7.9-gallon tank, about 10–11 hours at half load - About 198 lb - Two 20A 120V GFCI duplex outlets and a 30A 120/240V locking outlet (L14-30R) - Some versions include Generac's COsense, which shuts the unit down if carbon monoxide builds up to dangerous levels

Per running watt, the Honda costs about 90 cents and the Generac about 14 cents, so the inverter costs roughly six times as much for each watt. What you get for that money is lower noise, cleaner power, better fuel use at light loads and Honda's reputation for reliability.

The 240-volt question matters just as much as price. According to Consumer Reports, mid-size inverters in the 2,500–5,000 watt range usually lack the 240V connection a transfer switch needs. Big inverters like the EU7000iS have one, but you pay for it. Most conventional generators in this size class include it as standard.

You can also connect two compatible inverters in parallel, as long as the manufacturer approves both units for parallel use. Running a pair gives you combined wattage, and you can carry each unit separately.

05Safety, Whichever Type You Choose

Both kinds of generator produce carbon monoxide, and both can be deadly if they're used the wrong way.

• Keep it at least 20 feet from the house, outdoors, with the exhaust pointed away from doors, windows and vents.
• Never run it in a garage, basement, shed or porch enclosure, even with the doors or windows open. Open doors and windows don't give enough ventilation.
• **Install CO alarms** on every level of the house and outside sleeping areas. CO has no color and no smell, so the alarm is how you'll know.
• Connect to the house the right way. Use heavy-duty extension cords to individual appliances, or have a licensed electrician install a transfer switch or interlock kit. Never backfeed through a wall outlet. It can energize the utility lines and endanger line workers, and it can damage your home and the generator.

Fall is a good time to test your CO alarms, so do it when you set the clocks back.

06Which One Should You Buy?

Match the machine to your outage list:

• Your city-water house runs a gas furnace, the fridge, a router and chargers: a 2,000–3,500 watt inverter. It's quiet, easy on fuel and gentle on electronics.
• You have a well pump, an electric water heater, or you want a transfer switch for your panel on a budget: a conventional generator in the 7,000–8,000 watt range with a 120/240V locking outlet.
• You want whole-home comfort with quiet, clean power, and the budget allows: a large inverter with 240V, such as the EU7000iS.
• You want flexibility: two small inverters in parallel. You can run one on quiet nights and both when the load goes up, and each one is light enough to carry. One big conventional unit costs less per watt and handles 240V loads, but it's heavy and loud. Before you count on a parallel pair for a well pump, check whether the paired setup gives you a 240V outlet.

As a rough guide, about 2,000 watts or less covers the basics, 2,000–5,000 watts covers a fridge plus larger appliances, and anything above 5,000 watts moves into whole-home backup.

Before you shop, walk through the house with a notepad. Write down the running and starting watts from the label on everything you want powered, and add them up. Your totals and whether you need 240V will tell you which type to buy. With Thanksgiving coming, picture a fridge full of turkey and fixings and size for that.

Sources (10)

• Electrical Trader: Inverter Generator Buying Guide
• Anker SOLIX: Inverter Generator vs Generator
• Consumer Reports: Pros and Cons of Inverter Generators
• Ace Tool: Honda EU7000iS
• Vanwall: Honda EU7000iS
• Murdoch's: Generac GP8000E
• Outbound Power: Generac GP8000E with COsense
• Generac: 8000W Portable Generator, Electric Start
• CPSC: Portable Generator Safety
• PIRG: Portable Generators Kill About 70 People Each Year