SnapEnergyLab

Appliance running costs

Space heater wattage and cost to run

A space heater draws close to its rated power whenever it is switched on — what varies is how hard it works and for how long. This page applies that thermostatic operation and shows every step of the arithmetic.

How much does a 1,500 W space heater cost to run?

A 1,500 W space heater switched on 8 hours per day at 100% duty cycle uses 12.0 kWh of electricity per day. At $0.180/kWh that is $2.16 per day, about $65.83 per average month and $789.98 per year — 4,389 kWh over the year. Those figures assume a typical wattage and a typical usage pattern; change any input below to match your own appliance and tariff.

Your inputs

Typical example — replace this 1,500 W default with your appliance’s actual rating for a better estimate.

A thermostat cuts this appliance out once at temperature — typical range around 100%.

Applies only to the 16 h a day the appliance is switched off, not to the idle part of the duty cycle.

Use the total variable rate from your bill, including delivery charges per kWh.

Scenario: hours per day

$65.83

per month (30.44-day average month)

12.0 kWh per day at 1,500 W

Estimate using typical assumptions
Per day
$2.16
kWh / month
366
kWh / year
4,389
Per year
$789.98

Average power across 24 hours

501 W

Daily energy spread evenly over 24 hours. Includes standby draw during switched-off hours when entered.

Cost per running hour

$0.270

While the appliance is actually drawing power.

Effective duty cycle

100%

Share of switched-on time at rated power.

Method

  1. 1,500 W = 1.5 kW
  2. 1.5 kW × 8 h/day = 12 kWh/day active
  3. 1 W standby × 16 h/day off = 0.016 kWh/day standby
  4. 12 + 0.016 = 12.016 kWh/day total
  5. 12.016 kWh × 0.18 USD/kWh = 2.163 USD/day
  6. 2.163 × 30.436875 days = 65.831 USD/month
  7. 12.016 kWh × 365.2425 days = 4388.754 kWh/year
  8. 4388.754 kWh × 0.18 USD/kWh = 789.976 USD/year

Monthly figures use a 30.44-day average month, 365.24-day average year.

Assumptions

  • Electricity rate of 0.18 USD/kWh (editable).
  • Calculations use a year of 365.2425 days and an average month of 365.2425 ÷ 12 = 30.436875 days, so twelve average months equal one year exactly. Displayed values are rounded to 365.24 and 30.44 days, and the rounded figures do not multiply out exactly.
  • 1 W standby draw for the 16 hours a day the appliance is switched off. Standby applies only outside the switched-on hours, not to the idle part of the duty cycle, and is included in every kWh and cost figure below.
  • Rated power is treated as real power in watts, not volt-amps.

What can change the result?

  • Whether the thermostat cycles the element off (duty cycle)
  • Heater setting — many units have 750 W and 1,500 W modes
  • Room size, insulation and outdoor temperature
  • Hours of use, which typically rise sharply in cold snaps

$65.83/mo · 366 kWh/mo

How a space heater actually draws power

A resistance heater has no efficiency trick to play: while the element is on it draws essentially its full rated power. The only thing that reduces consumption is the thermostat cutting the element out once the room reaches temperature. In a draughty or large room a 1,500 W heater can run close to 100% of the time; in a small, well-insulated room the same heater may only be on a third of the time.

Treat the number below as the cost of the heater running at full power for the hours you set. If your heater has a thermostat and the room reaches temperature, lower the duty cycle to match — 50% duty roughly halves the cost. Note that every watt of a resistance heater becomes one watt of heat, so no 'energy-saving' portable heater of the same wattage is cheaper to run.

How many watts does a space heater use?

Most plug-in electric space heaters sold in the US top out at 1,500 W, the practical limit for a standard 120 V household outlet circuit, and many have a low setting around 750 W. Smaller personal heaters draw less. While the element is on, every watt becomes heat, so the wattage sets the hourly cost directly.

Cost per hour assumes the element runs the whole hour. With a thermostat cycling it off, multiply by the share of time it is on — the duty-cycle field in the calculator does exactly that.
TypeTypical wattsCost per hour at full power ($0.180/kWh)Basis
Small personal / desk heaterabout 200–500 W$0.072 at 400 WIllustrative range
Typical heater on its low settingabout 750 W$0.135 at 750 WCommon low setting
Typical heater on its high setting1,500 W$0.270 at 1,500 WUsual maximum for US plug-in heaters

Cost at different usage patterns

All rows use 1,500 W at 100% duty and $0.180/kWh. Only the hours change.

Generated by the same energy engine that powers the calculator above.
Hours per daykWh per dayPer dayPer monthPer year
4 h/day6.02 kWh$1.08$32.98$395.78
6 h/day9.02 kWh$1.62$49.41$592.88
8 h/day12.0 kWh$2.16$65.83$789.98
12 h/day18.0 kWh$3.24$98.68$1,184

Cost across the typical wattage range

Units in this category typically range from 750 W to 1,500 W. All rows use 8 h/day at 100% duty.

Source for the range: Nameplate ratings of portable resistance heaters sold in North America (2026-01).
Power ratingkWh per dayPer dayPer monthPer year
750 W6.02 kWh$1.08$32.96$395.51
1,500 W12.0 kWh$2.16$65.83$789.98
1,500 W12.0 kWh$2.16$65.83$789.98

The decision that changes this cost: let the thermostat cycle in a smaller room

A resistance heater at full power converts every watt to heat, so the only saving is running it less. In a small, well-insulated room the thermostat reaches setpoint and the element can be off half the time — modelled here as 50% duty instead of continuous running.

Both rows computed by the same engine at $0.180/kWh — only the change described above differs.
ScenariokWh per yearCost per year
Space heater as defaulted above4,389$789.98
Let the thermostat cycle in a smaller room2,197$395.51 — saves $394.46/yr (2,191 kWh)

Where a space heater sits in the home

Ranked by annual running cost at each appliance's default usage pattern, this space heater is number 2 of 16 in the SnapEnergyLab catalogue — $789.98 per year at $0.180/kWh. The appliances either side of it:

Every appliance at its own default wattage, hours and duty cycle, same engine, same rate.
RankAppliancekWh per yearCost per year
#1Hot tub7,100$1,278
#2Space heater (this page)4,389$789.98
#3Pool pump3,214$578.54

Worth knowing

Marketing claims about 'efficient' resistance heaters do not change electricity use: all resistance heaters are essentially 100% efficient at turning electricity into heat.

Worth knowing

Fan-only or eco modes draw far less than the rated element power.

Your next decision

Your next decision

Other appliance running costs

Electricity cost tools

Defaults on this page come from the published default registry and the formulas are documented in the methodology.