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What Size Generator to Run a Space Heater?

Last updated:

Fact-checked by Marcus Hayes, Master Electrician (License #CA-EL-89241), 15 years generator installation experience.

Space heaters are power-hungry resistive loads that draw 1,500W continuously. Unlike motor-driven appliances, they have no starting surge — but their constant high draw makes them one of the most demanding appliances to run on a generator. This guide helps you size correctly and understand the fuel costs involved.

Key Takeaways

  • A 1,500W space heater needs at least a 2,000W generator; a 3,000W+ generator is recommended for headroom.
  • Space heaters are resistive loads with no starting surge — running watts equal starting watts.
  • A 2,000Wh solar generator runs a space heater for only 1.3 hours — battery backup is impractical for heating.
  • A furnace blower (600W) uses 3x less power than a space heater and heats the whole house — always prefer it.
  • Running a space heater on a gas generator costs about $1/hour in fuel — $25/day for continuous use.

Space heater wattage explained

A standard space heater draws 1,500W on its high setting and 750W on low. Because space heaters use resistive heating elements (not motors), there is no starting watt surge — the running watts and starting watts are the same. This means you only need a generator with 1,500 running watts, not 3,000+ starting watts like you would for a motor-driven appliance.

Why a furnace blower is better than a space heater

If you have a gas furnace, power the furnace blower (600W running, 1,800W starting) instead of a space heater (1,500W continuous). The furnace blower uses 60% less power, heats the entire house through existing ductwork, and runs intermittently (not continuously like a space heater). A 2,000W generator can run a furnace blower plus a refrigerator and lights — the same generator would struggle with a space heater alone.

The only situation where a space heater makes sense on a generator is when you have electric heat (no gas furnace) and need to warm a single room. In that case, use a 3,000W+ generator, run the space heater on medium (750W) to conserve fuel, and insulate the room by closing doors and hanging blankets over windows. Expect to refuel every 6 to 8 hours.

Frequently Asked Questions

What size generator do I need to run a space heater?
A 1,500W space heater needs a generator with at least 1,500 running watts. Since space heaters are resistive loads with no starting surge, you do not need extra starting watts. A 2,000W generator like the Honda EU2200i (1,800W) can run a 1,500W space heater, but it will be near maximum capacity. A 3,000W+ generator is recommended for headroom.
Can a solar generator run a space heater?
Yes, but not for long. A 1,500W space heater draws 1,500Wh per hour. A 2,000Wh solar generator runs a space heater for about 1.3 hours. A 4,000Wh unit runs it for 2.7 hours. Space heaters are very energy-intensive — a battery backup is better used for a furnace blower (600W) which uses 4x less power and heats the whole house.
Can a 2000W generator run a space heater?
A 2,000W generator with 1,800 running watts (like the Honda EU2200i) can technically run a 1,500W space heater, but it will be running at 83% capacity continuously. This is not recommended — the generator will be loud, hot, and fuel-hungry. A 3,000W+ generator is better for running a space heater with headroom for other loads.
Is a space heater a good use of generator power?
No. A space heater draws 1,500W continuously, which is 3x more than a furnace blower (600W) that heats the entire house. If you have a gas furnace, use the generator to power the furnace blower instead. If you only have electric heat, a space heater is your only option, but expect high fuel consumption and short runtime.
How much fuel does it cost to run a space heater on a generator?
Running a 1,500W space heater on a 3,000W gas generator burns about 0.3 gallons of gasoline per hour. At $3.50/gallon, that is $1.05/hour or $25/day for continuous use. A 4,000Wh solar generator runs a space heater for 2.7 hours on a full charge with zero fuel cost if recharged with solar.