How Much Energy Does a Space Heater Use?
- How Many Watts Does a Space Heater Use?
- How Much Energy Does a Space Heater Use for 24 Hours?
- How Much Does It Cost to Run a 1500 Watt Heater for 24 Hours?
- Is It Safe to Leave a Space Heater on All Night?
- Does Leaving a Space Heater Plugged In Use Electricity?
- What Size of a Generator Is Good for a Space Heater?
- Final Words
A space heater feels like a small home comfort, but it might have big energy habits. Whether it hums quietly in your office corner or blasts warm air in your bedroom, it can pull serious electricity. Before cozy turns costly, let’s dig into how much power a space heater really consumes—and what it means for your bill, your safety, and your backup plan.
How Many Watts Does a Space Heater Use?
Most space heaters fall into one of two categories: low wattage for small areas or high wattage for big warmth. The average is around 1500 watts, but that’s not a hard rule. A breakdown of common heater wattages:
Heater Type | Wattage Range | Typical Use Case |
Personal desktop heater | 200–500W | Small office cubicles |
Small ceramic heater | 750W | Bedrooms or small rooms |
Standard fan-forced heater | 1500W | Living rooms, large bedrooms |
Oil-filled radiator heater | 1000–1500W | Long-term heating, more even warmth |
Infrared quartz heater | 1000–1500W | Spot heating, directional warmth |
Note: Some models allow adjustable settings, like switching between 750W and 1500W, so your usage may vary based on the heat level selected.
How Much Energy Does a Space Heater Use for 24 Hours?
Wattage is just the start. To get real usage, you need to know how long it runs—and then do a little math. Let’s take the common 1500W heater as an example. Here’s what 24 hours of nonstop operation looks like:
1500 watts = 1.5 kilowatts
1.5 kW × 24 hours = 36 kWh (kilowatt-hours)
Now apply that to different heater types:
Heater Wattage | Daily Energy Use (24h) | |
500W | 12 kWh | |
750W | 18 kWh | |
1000W | 24 kWh | |
1500W | 36 kWh | |
That’s a lot of power for one device. If you're using it daily through winter, the numbers stack up fast.
How Much Does It Cost to Run a 1500 Watt Heater for 24 Hours?
Electricity rates in the U.S. range widely depending on state and provider. A typical residential rate is around $0.1595 per kWh in January 2025, here’s what it costs to run a 1500W space heater:
36 kWh × $0.1595 = $5.74 per day Over 30 days (running continuously), that totals to:
$$5.74 × 30 = $$172.20 per month Now, here’s how different heater wattages compare under the same rate:
Wattage | 24h Use (kWh) | Daily Cost |
500W | 12 kWh | $1.91 |
750W | 18 kWh | $2.87 |
1000W | 24 kWh | $3.83 |
1500W | 36 kWh | $5.74 |
And you can expect the cost of running a 1500 watt space heater by different US states:
State | ¢/kWh | Daily Cost ($) |
Hawaii | 40.51 | 14.58 |
California | 30.22 | 10.88 |
Rhode Island | 31.66 | 11.4 |
Massachusetts | 30.08 | 10.83 |
Connecticut | 30.06 | 10.82 |
Alaska | 24.74 | 8.91 |
New York | 25.31 | 9.11 |
Maine | 26.13 | 9.41 |
Maryland | 18.26 | 6.57 |
Vermont | 21.95 | 7.9 |
New Jersey | 19.68 | 7.09 |
New Hampshire | 23.4 | 8.42 |
Michigan | 18.5 | 6.66 |
Wisconsin | 17.42 | 6.27 |
Illinois | 15.81 | 5.69 |
Pennsylvania | 17.58 | 6.33 |
Nevada | 13.92 | 5.01 |
Delaware | 15.52 | 5.59 |
Arizona | 14.75 | 5.31 |
Florida | 14.43 | 5.19 |
Texas | 14.68 | 5.28 |
Georgia | 13.52 | 4.87 |
North Carolina | 12.47 | 4.49 |
South Carolina | 13.81 | 4.97 |
Virginia | 14.04 | 5.05 |
West Virginia | 14.47 | 5.21 |
Indiana | 14.65 | 5.27 |
Colorado | 15.01 | 5.4 |
New Mexico | 13.73 | 4.94 |
Washington | 11.79 | 4.24 |
Oregon | 14.44 | 5.2 |
Ohio | 15.64 | 5.63 |
Minnesota | 14.53 | 5.23 |
Tennessee | 12.7 | 4.57 |
Mississippi | 12.62 | 4.54 |
Alabama | 15.05 | 5.42 |
Utah | 12.12 | 4.36 |
Missouri | 11.19 | 4.03 |
Iowa | 12.05 | 4.34 |
Arkansas | 11.25 | 4.05 |
Louisiana | 11 | 3.96 |
Oklahoma | 11.02 | 3.97 |
North Dakota | 9.93 | 3.57 |
Montana | 11.41 | 4.11 |
South Dakota | 12.09 | 4.35 |
Nebraska | 10.56 | 3.8 |
Kansas | 13.32 | 4.8 |
Idaho | 10.82 | 3.9 |
Kentucky | 12.6 | 4.54 |
Wyoming | 11.69 | 4.21 |
District of Columbia | 18.83 | 6.78 |
Of course, heaters don’t always run 24/7. Many cycle off and on as the room hits the target temperature, especially models with built-in thermostats.
Is It Safe to Leave a Space Heater on All Night?
Yes, but only with strict conditions:
The heater must have overheat protection and a tip-over shutoff.
It should never be placed near blankets, curtains, or furniture.
Always plug it directly into a wall outlet, not a power strip.
Make sure it has ETL or UL certification. If all these boxes are checked, the heater is safer to run while you sleep. But it’s still wise to avoid running it unattended for long periods. If your home gets cold at night, preheat the room and switch off the heater before bed—or use a heater with a programmable timer.
Does Leaving a Space Heater Plugged In Use Electricity?
If the heater is off and not running, it doesn’t draw meaningful electricity. But if it’s in standby mode or has a digital display, it could still draw a very small amount, typically under 1 watt. That said, most of the time, your bill won’t notice the difference unless dozens of gadgets are doing the same thing all day. Still, for safety—especially in older homes—it’s smart to unplug when not in use. Fires linked to space heaters usually stem from overheating or placement errors, not from passive plugged-in devices.
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What Size of a Generator Is Good for a Space Heater?
Heater Size | Generator Size (Min) | Generator Size (Recommended) |
500W | 800W | 1000–1200W |
1000W | 1300W | 1500–2000W |
1500W | 2000W | 3000W+ (if other devices too) |
When the grid goes down, and the cold creeps in, space heaters might be your go-to heat source. But not every generator can handle that load. Let’s say you have a 1500W heater. Add at least 10–20% headroom, since generators shouldn’t run at 100% capacity continuously. So for one heater:
Minimum output = 1800–2000W (2kW) generator A portable generator like the EcoFlow DELTA 2 Max fits well here. It delivers 2400W AC output (surge 4800W) and can power a 1500W heater plus lighting and small electronics with no issues. If needed, it even supports expandable capacity up to 6144Wh for overnight heating. Now, if you want to run other essentials (lights, phone chargers, maybe a fridge), go up to 3000–4000W to keep things running smoothly. For full-home heating support or extended blackout scenarios, the EcoFlow DELTA Pro stands out. With 3600W rated output (boostable to 4500W), solar + AC charging, and up to 25kWh capacity when expanded, it’s powerful enough to handle multiple space heaters, fridges, and critical electronics all at once.
Final Words
A space heater can be a friend if you are in need—but a costly one if used blindly. Know your wattage, measure your hours, and pick your power source carefully. Comfort doesn’t need to come with a surprise electric bill or fire hazard.