The short answer
- A portable setup (a 9,500-watt dual-fuel generator plus an interlock and power inlet installed by an electrician) runs about $1,600 to $3,500. It covers the essentials, but you start it, fuel it and run it yourself.
- A 22 kW standby generator with an automatic transfer switch is commonly $10,000 to $15,000 installed. It starts on its own and can run central air and most of the house on natural gas or propane.
- Rare, short outages favor a portable. Long or frequent outages, a well or sump pump you can't lose, medical equipment, or nobody home to haul fuel favor a standby.
- Both need a transfer switch or listed interlock to feed house circuits. Never backfeed through an outlet.
- Carbon monoxide is the big risk with portables: run them outdoors only, at least 20 feet from the house, with CO alarms inside.
The difference in one paragraph
A portable generator lives in the garage or shed. When the power goes out, you roll it outside, fuel it with gasoline or a propane tank, start it and either run extension cords to appliances or plug it into a power inlet that feeds chosen circuits. A home standby generator is bolted to a pad next to the house and piped to your natural gas line or a propane tank. An automatic transfer switch watches the utility power. When it drops, the generator starts itself and takes over, usually within seconds, whether you're home or not.
| Portable | Home standby | |
|---|---|---|
| Running watts | 1,800 to 9,500 (inverter or open frame) | 10 to 26 kW |
| Fuel | Gasoline, propane tanks, or both | Natural gas or propane, from the house supply |
| Starts | By hand or push button, outdoors, in the storm | By itself; tests itself each week |
| Runs | About 8 hours per gasoline tank at half load (9,500 W model) | Days on natural gas; on propane, as long as the tank lasts |
| Can power | Fridge, sump, furnace fan, lights; a well pump or window AC on larger units | Central AC and most or all of the house |
| Installed cost | $600 to $3,500 | About $7,000 to $15,000+ |
| Main safety risk | Carbon monoxide from misplacement; backfeeding | Exhaust near windows or air intakes; gas and wiring done wrong |
What each costs over ten years
The sticker price is only part of it. A portable needs a safe way to connect to the house, and a standby needs a pad, a gas line, a permit and yearly service. These are planning ranges from 2026 retail listings, installer price guides and HomeAdvisor's maintenance data, not quotes. Your electrician's bid will vary with the distance to the panel, gas line size and local permit fees.
| Setup | Upfront | Upkeep, 10 years | 10-year total |
|---|---|---|---|
| 2,200 W inverter, cords only | $600 to $1,200 | Oil and plugs, DIY | About $700 to $1,400 |
| 9,500 W dual-fuel portable + interlock and inlet | $1,600 to $3,500 | Oil, plugs, filters, DIY | About $2,000 to $4,000 |
| 10 to 14 kW standby, essentials only | About $7,000 to $12,000 | $1,700 to $4,000 (pro service) | About $9,000 to $16,000 |
| 22 kW standby, whole house | $10,000 to $15,000 | $1,700 to $4,000 (pro service) | About $12,000 to $19,000 |
The standby service figure comes from HomeAdvisor's 2025 data: $171 to $395 a visit, $273 on average, once a year. A 22 kW standby unit alone is about $6,000 to $7,000; the rest of the installed price is the transfer switch, concrete or composite pad, gas piping, wiring, permit and labor. If your gas meter is too small for the generator's full-load draw (a 22 kW unit can pull about 311 cubic feet an hour on natural gas), the utility may need to upgrade it, which can add cost and weeks of lead time.
What each one can power
Size comes first, because it often makes the decision for you. Our generator size calculator adds your running watts and the biggest motor's starting surge. With its default essentials (refrigerator, sump pump, furnace fan, microwave, lights, TV and internet), it lands on a portable of about 5,000 running watts. Adding a well pump moves that to about 7,500.
Central air is where portables run out of room. A 2-ton central AC needs about 3,800 running watts and close to 5,000 more to start, which usually points to a standby of about 14 kW once the essentials are added. A soft-start kit on the compressor can sometimes bring it within reach of a large portable. If you're not sure what size your AC is, the AC size calculator gives the tonnage a room or house needs.
Two other limits matter more than people expect:
- 240-volt loads. Well pumps, central AC, electric ranges and water heaters often run on 240 V. A portable needs a 240 V outlet and a panel connection to run them. Extension cords won't do it.
- Hardwired loads. A furnace blower, a well pump and a sump pump on a dedicated circuit have no plug. Without an interlock or transfer switch, a portable can't run them.
Fuel: storage, run time and cost
Fuel is where the two differ most in daily life. A 9,500-watt portable at half load burns about 0.8 gallons of gasoline an hour, so a three-day outage takes about 58 gallons. That's roughly nine trips to refill a 6.6-gallon tank, and many gas stations can't pump without power. Gasoline also goes stale in storage, so it needs stabilizer and rotation. Dual-fuel portables can switch to propane tanks, which keep indefinitely, though a 20-pound tank lasts only 6 to 7 hours on that size of generator.
A standby unit on natural gas simply keeps running as long as the gas utility delivers. On propane, the tank is the limit. Propane tanks are filled to about 80% to leave room for expansion, so a 500-gallon tank holds about 400 gallons. At half load, a 22 kW unit burns about 2.45 gallons an hour, which works out to roughly 6.8 days on a full 500-gallon tank and 3.4 days on a 250-gallon one. At lighter loads it lasts longer.
| Generator and fuel | Fuel used | Per hour | 3-day outage |
|---|---|---|---|
| Portable, gasoline ($4.27/gal) | 61 gal | $3.63 | $261 |
| Standby, propane ($2.73/gal) | 79 gal | $3.00 | $216 |
| Standby, natural gas ($1.61 per 100 cu ft) | 7,560 cu ft | $1.69 | $122 |
Fuel cost alone rarely decides it. A few hundred dollars per long outage is small next to the price gap between the two setups. What matters is whether you can get, store and pour that much fuel during a storm.
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Connecting to the house: cords, interlocks and transfer switches
The National Electrical Code (NFPA 70, Article 702) requires transfer equipment whenever a generator feeds a home's wiring. The equipment keeps the house disconnected from the utility while the generator runs, so power can't flow back onto the lines. A "double-male" cord plugged into a wall or dryer outlet does the opposite. It can electrocute line workers who think the lines are dead, and it can start a fire when grid power returns.
| Method | How it works | Installed cost |
|---|---|---|
| Extension cords | Outdoor-rated, heavy-gauge cords from the generator to plug-in appliances only | Cords only |
| Interlock kit + power inlet | A listed plate on your panel that lets the generator breaker turn on only when the main is off; you choose circuits by hand | About $400 to $850 |
| Manual transfer switch | A small panel pre-wired to 6 to 10 chosen circuits, each with its own switch | About $400 to $1,300 |
| Automatic transfer switch | Senses the outage, starts the standby generator and switches over; switches back when power returns | Usually part of the standby package |
Any connection to the panel is a job for a licensed electrician with a permit. Grounding and neutral bonding have to match the generator and the switch, and the inspector will check both. Standby installs usually need a gas permit too, and some utilities ask to be told about any generator tied to the house. With a standby, ask about load management: modules that shed the AC or water heater for a moment when a big motor starts, so a smaller generator can cover the house.
Safety: carbon monoxide and placement
The CDC says more than 400 Americans die each year from unintentional carbon monoxide poisoning not linked to fires, more than 100,000 visit an emergency room and more than 14,000 are hospitalized. CPSC estimates that about 85 of those deaths each year come from portable generators. CO has no smell or color. The rules are simple:
- Run a portable outdoors only, at least 20 feet from the house, with the exhaust pointed away from windows, doors and vents.
- Never in a garage, basement, crawlspace, shed, porch or carport, even with the doors open. A fan doesn't make it safe.
- Put battery-powered or battery-backup CO alarms on every level and test them monthly.
- When you buy a portable, look for a CO shut-off certified to PGMA G300-2023 or UL 2201-2023.
- Headache, dizziness, weakness, nausea or confusion while a generator runs means everyone goes outside and someone calls 911.
Standby units are safer by design, but not immune. After Hurricane Ida, CPSC staff found standby exhaust that traveled 25 feet or more and set off CO alarms inside homes. Generac says to keep its home standby units at least 5 feet from windows, doors, vents and window wells, and its manuals set minimum clearances to the wall behind the unit. Local codes and your inspector can require more. Don't put either kind under a deck or overhang, and keep CO alarms working even with a standby.
Noise, upkeep and lifespan
- Noise. A 22 kW air-cooled standby is listed at about 67 dBA at 23 feet under normal load, and about 57 dBA during its low-speed weekly self-test. Open-frame portables are generally louder than inverter models of similar size. Check the manufacturer's dBA rating at 23 feet (7 meters), and check any local noise ordinance or HOA rules before you place a standby near a property line.
- Upkeep. Portables need oil changes, a fresh spark plug and a monthly run under load, plus stabilized or fresh fuel. Standby units exercise themselves weekly but still need a yearly service (oil, filters, plugs, battery check) to keep the warranty valid. Generac's 22 kW unit carries a 5-year limited warranty.
- Lifespan. Standby units typically run only a few dozen hours a year, so age, corrosion and parts availability usually end their life before engine hours do. A portable that sits for years with old gasoline in the carburetor is the most common failure of all.
Which one fits your home
| A portable fits if | A standby fits if |
|---|---|
| Outages are rare and last hours, not days | Outages are frequent or last for days |
| You need the fridge, sump, furnace fan and lights | You need central AC, a well pump or the whole house |
| Someone able-bodied is home to set it up and refuel | The house is often empty, or hauling fuel is hard for you |
| You rent, or may move soon | You own and plan to stay |
| Your budget is under about $3,500 | Someone in the home relies on powered medical equipment |
There's a third option for short outages: a home battery. It's silent, makes no exhaust and switches over instantly, but it runs out of stored energy unless solar panels recharge it. Our home battery size calculator shows how many kWh your essentials need for a given outage. Some homeowners pair a small portable with a battery and recharge the battery from the generator for a few hours a day.
Common mistakes
- Shopping by the starting-watts number printed in large type on the box. Size by running watts.
- Buying a portable with no plan to connect it. Without an interlock or transfer switch, your furnace and well pump stay off.
- Running the generator close to the house to keep it out of the rain. Use a generator tent or canopy made for it, 20 feet out.
- Never testing it. Run a portable under load for 20 minutes a few times a year. Check that a standby's weekly self-test is actually running.
- Oversizing a standby. Load management can let a smaller unit cover the house for thousands less.
Common questions
Is a standby generator worth the money?
It depends on your outages and your needs. If you lose power for days at a time, need central air, a well pump or medical equipment, or are often away from home, a standby generator's automatic start and steady fuel supply are worth a lot. For rare, short outages, a portable with an interlock covers the essentials for a fraction of the cost.
How much does a whole-house generator cost installed?
A 22 kW standby generator with an automatic transfer switch commonly costs about $10,000 to $15,000 installed, including the pad, gas line, wiring, permit and labor. Smaller 10 to 14 kW units that cover the essentials run roughly $7,000 to $12,000. Gas meter upgrades and long wiring runs add to that.
Can a portable generator power a whole house?
Usually not all at once. A large portable of about 9,500 running watts can run the refrigerator, sump pump, furnace fan, lights and a well pump or window AC through an interlock. Central air, an electric range and an electric water heater together need a standby unit or careful switching of loads one at a time.
Do I need a transfer switch for a portable generator?
Only if you want it to power house circuits. Extension cords to plug-in appliances need no switch. To run hardwired loads like a furnace or well pump, you need a transfer switch or a listed panel interlock with a power inlet, installed by a licensed electrician. Never plug a generator into a wall outlet.
How long will a standby generator run on propane?
A 500-gallon tank filled to about 80 percent holds around 400 gallons. A 22 kW generator at half load burns about 2.45 gallons an hour, so the tank lasts roughly 6 to 7 days. A 250-gallon tank lasts about half as long. Lighter loads stretch it further.
Can I run a generator in the garage with the door open?
No. The CPSC and CDC both say never to run a generator inside a garage, basement, shed or any enclosed space, even with doors and windows open. Run it outdoors at least 20 feet from the house, with the exhaust pointed away from openings, and keep battery-powered CO alarms inside.
How often does a standby generator need maintenance?
Most manufacturers call for service once a year or after a set number of run hours, whichever comes first, plus more after a long outage. A professional visit averaged about $273 in HomeAdvisor's 2025 data. The generator also runs a short self-test every week.
Sources
Prices checked October 30, 2026; hookup prices checked November 1, 2026. Interlock and transfer switch prices come from HomeGuide. Equipment, installation and portable upkeep ranges are HomeOutlay estimates from 2026 retail listings and installer price guides, checked against HomeGuide's ranges; the fuel table uses the same fuel-per-kWh rates as our generator size calculator.
- CDC, About carbon monoxide poisoning (reviewed Oct. 26, 2026): more than 400 deaths, 100,000 emergency visits and 14,000 hospitalizations a year; symptoms; 20-foot guidance.
- CPSC, generator CO and fire hazards (May 27, 2026): 20-foot rule, CO alarms, PGMA G300-2023 and UL 2201-2023 models.
- CPSC, CO fatalities report (2022): about 85 generator CO deaths a year (2017–2019 average).
- CPSC staff report on stationary generators (June 3, 2025): standby exhaust reaching 25 feet or more after Hurricane Ida.
- Generac, clearance requirements: 5 feet from windows, doors, vents and window wells.
- Generac 22 kW standby specifications: 221 cu ft/h (natural gas) and 2.45 gal/h (propane) at half load, 311 cu ft/h at full load, 5-year limited warranty. Sound levels of 67 dBA at normal load and 57 dBA in quiet test, at 23 feet, from Generac spec sheets as published by retailers.
- HomeGuide, transfer switch installation cost: interlock kit $400 to $850 installed, manual transfer switch $400 to $1,300, automatic $600 to $2,500.
- HomeGuide, whole house generator cost (updated December 30, 2025): portables $500 to $2,500, a 22 kW Generac unit about $5,000, installation labor $3,000 to $5,000 or $5,000 to $12,000+ above 20 kW.
- Westinghouse WGen9500DF specifications: 8 hours on 6.6 gallons of gasoline and 7 hours on a 20 lb propane tank at half load.
- OSHA, Using Portable Generators Safely, and Generac on backfeeding. Transfer equipment: NFPA 70 (National Electrical Code), Article 702.
- HomeAdvisor, whole-house generator maintenance cost (2025): $171 to $395, average $273.
- Fuel prices: EIA gasoline ($4.27/gal) and EIA propane ($2.73/gal), week of Oct. 26, 2026; natural gas $16.09 per thousand cu ft, 2026 residential average, EIA Short-Term Energy Outlook, October 2026.