What will a 12,000-watt generator run?
With 12,000 running watts, a generator can run a well pump, a sump pump, a furnace blower, a refrigerator, a freezer, a microwave, lights, Wi-Fi and a TV together on the generator makers' wattage charts, using about 5,846 of its watts. That leaves room for an electric water heater as well (wired in, through a transfer switch). It can't run a 3-ton central air conditioner, which needs about 18,000 watts to start.
We take 12,000 as running (rated) watts. The generators we compare make 1.22 to 1.35 times their running watts to start, so we allow 14,640 starting watts, the cautious end. Your generator's own starting (peak) figure is on its label.
Outage combinations
| Running at once | Running W | Starting W | 12,000 W? |
|---|---|---|---|
| Refrigerator, lights, Wi-Fi, TV and phones | 1,046 | 2,896 | Yes |
| Gas furnace blower, refrigerator, lights and Wi-FiWired in: needs a transfer switch | 1,428 | 3,278 | Yes |
| Sump pump, refrigerator, lights and Wi-Fi | 1,828 | 3,828 | Yes |
| Window air conditioner, refrigerator, lights and Wi-Fi | 2,028 | 4,028 | Yes |
| Well pump, refrigerator and lightsWired in: needs a transfer switch | 1,810 | 3,810 | Yes |
| Refrigerator, microwave and coffee maker | 3,450 | 5,300 | Yes |
| CPAP with humidifier, refrigerator, lights and phones | 947 | 2,797 | Yes |
| Furnace blower, refrigerator, freezer, sump pump, lights, Wi-Fi and TVWired in: needs a transfer switch | 3,326 | 5,326 | Yes |
| Well pump, sump pump, furnace blower, refrigerator, freezer, microwave, lights, Wi-Fi and TVWired in: needs a transfer switch | 5,846 | 7,846 | Yes |
| Electric water heater, refrigerator, furnace blower and lightsWired in: needs a transfer switch | 6,410 | 8,260 | Yes |
| 3-ton central air conditionerWired in: needs a transfer switch | 6,000 | 18,000 | No |
"Check labels": it runs once everything has started, but the charts' cautious start-up surge is more than 14,640 watts. Modern appliances often start with less, so check your generator's starting watts and the amps on the appliance label (amps × 120 = watts).
One appliance at a time
| Appliance | Running W | Starting W | 12,000 W? |
|---|---|---|---|
| Refrigerator | 750 | 2,600 | Yes |
| Freezer (chest or upright) | 750 | 2,600 | Yes |
| Gas furnace blower (1/3 to 1/2 HP)Wired in: needs a transfer switch | 600 | 1,800 | Yes |
| Sump pump (1/2 HP) | 1,000 | 3,000 | Yes |
| Well pump (1/3 to 1/2 HP)Wired in: needs a transfer switch | 1,000 | 3,000 | Yes |
| Window air conditioner (10,000 BTU) | 1,200 | 3,200 | Yes |
| Microwave | 1,500 | 2,800 | Yes |
| Coffee maker | 1,200 | 1,200 | Yes |
| Electric space heater | 1,500 | 1,500 | Yes |
| CPAP with heated humidifier (and heated tube) | 67 | 67 | Yes |
| Home oxygen concentrator | 325 | 325 | Yes |
| Electric water heater (50 gallon, 240V)Wired in: needs a transfer switch | 5,000 | 5,000 | Yes |
| Central air conditioner (3 ton)Wired in: needs a transfer switch | 6,000 | 18,000 | No |
Want your own list? Use the generator calculator →
Generators around 12,000 watts
Ready.gov says to use a generator ONLY outdoors, at least 20 feet away from windows, never in a home or garage. Fit carbon monoxide alarms with battery backup on every level of your home. Never plug a generator into a wall outlet: wired-in loads need a transfer switch fitted by a qualified electrician. See our generator safety guide.
Questions
Will a 12,000-watt generator run a refrigerator?
Yes. On generator makers' charts a refrigerator needs up to 750 running watts and about 2,600 watts to start, within a 12,000-watt generator's running watts and the roughly 14,640 starting watts generators of this size make.
Can a 12,000-watt generator run a house?
It can run a well pump, a sump pump, a furnace blower, a refrigerator, a freezer, a microwave, lights, Wi-Fi and a TV, not the whole house. A 3-ton central air conditioner needs about 18,000 watts to start, more than it makes. Wired-in loads such as a furnace or well pump need a transfer switch fitted by a qualified electrician.
Will a 12,000-watt generator run central air?
No. DTE Energy's guide puts a 3-ton central air conditioner at 6,000 running watts and about 18,000 watts to start. That takes a standby generator sized by an electrician.
Other sizes
Sources (4)
- Champion Power Equipment: Choosing a generator (wattage chart)
- DTE Energy: Appliance usage guide and generator worksheet
- Energy Star certified product datarefrigerators, freezers, TVs, room air conditioners, light bulbs
- Ready.gov: Power outages