How much does it cost to run an under-desk space heater?
An under-desk space heater is a compact radiant or convection unit designed to warm your personal workspace rather than an entire room, typically drawing 700 to 1,500 watts of power. Because they operate at high wattage for focused, localized heating, they can have a noticeable impact on your energy consumption during the winter months when used daily.
Under-Desk Space Heater running cost calculator
- Per day
- $0.64
- Per month
- $6.38
- Per year
- $76.50
- CO₂ / year
- 180 kg
Based on 450 kWh per year. Adjust the price per kWh to match your latest electricity bill for an exact figure.
At 750 watts used 5 hours a day, an under-desk space heater costs about $0.64 per day, $6.38 per month and $76.50 per year on an average rate of 17¢ per kWh — roughly 450 kWh and 180 kg of CO₂ over a year. Enter your own electricity rate and usage in the calculator above for a figure matched to your bill.
The energy consumption of an under-desk heater depends primarily on its wattage setting and how long you keep it running. Most models offer multiple power levels—often 750W, 1,000W, and 1,500W—allowing you to dial down the output when you're not sitting directly in front of it or when the room temperature is mild. Many people make the mistake of running their heater at maximum wattage all day, even during warmer parts of the day or when they step away from their desk. A practical approach is to start at the lowest setting that keeps you comfortable, then increase only if needed; the difference in usage between 750W and 1,500W adds up quickly over a season.
Placement and design significantly affect both comfort and efficiency. An under-desk heater works best when positioned close to where you sit, as radiant models heat objects and people directly rather than warming the entire room's air. Avoid placing the unit where air circulation is blocked by desk clutter, as this forces the heater to work harder to distribute warmth. Convection models (which blow warm air) can dry out office air and sometimes create drafts, while radiant heaters provide steadier, more comfortable warmth without the noise. If your office space has poor insulation or drafty windows, a space heater becomes less effective because heated air escapes, leading to longer run times and higher costs.
When evaluating models, look for units with built-in thermostats and timers, as these features allow automatic shut-off when the desired temperature is reached or at a preset time. Some heaters lack these controls entirely, forcing you to manually turn them off—a common reason people inadvertently leave them running longer than necessary. Safety certifications like ETL or UL are important, particularly for under-desk models where fabric, paper, and other office materials may be nearby. Overheating protection and tip-over switches prevent fire hazards. Ceramic elements tend to heat up and cool down faster than coiled resistance wire, giving you better control over temperature swings.
The actual cost impact depends on how frequently you use the heater and whether it's truly supplementing room heat or replacing a centralized system. If your building's heating is set low to cut costs, an under-desk heater might let you work comfortably without raising the thermostat for the whole space—a genuine savings strategy. However, if you're adding heat on top of adequate room heating just to be extra warm, you're running two heating sources simultaneously, which is wasteful. Honest assessment of your comfort needs and your workspace's baseline temperature will help you use the heater only when justified, keeping its running time and seasonal cost in check.
Frequently asked questions
- Should I use my under-desk heater all day, or only when I'm cold?
- Use it only when you're actively seated at your desk and feel cold. Turning it off during lunch breaks, meetings away from your desk, or when room temperature rises naturally can significantly reduce its runtime and energy impact over a season. A timer function helps automate this discipline.
- Why does my under-desk heater feel less effective over time?
- The most common cause is dust or debris blocking the heating element or air vents. Over a heating season, dust accumulates and reduces heat output, forcing the heater to work harder to reach the same comfort level. Regular gentle cleaning with a dry cloth or soft brush keeps it efficient. Another factor is habituation—your body adapts to the warmth, so you may perceive it as weaker even though it's performing normally.
- Is it cheaper to run a space heater or raise the building thermostat?
- If your building's central heating serves many rooms, raising the thermostat heats unoccupied spaces and exterior walls, wasting energy. A space heater focused on just your desk is more efficient for personal comfort. However, if the building is already adequately warm and you're adding extra heat for preference alone, you're paying extra. The savings only apply if the heater truly replaces—not supplements—central heating.
- What wattage setting should I actually use?
- Start at the lowest setting (usually 750W) and only increase if you remain cold after 10-15 minutes. Many users jump straight to maximum wattage out of habit or impatience, but the mid-range setting (1,000W) is comfortable for most people in a moderately cool office. Lower settings are quieter, safer, and reduce energy consumption without sacrificing comfort for typical use.
- Can an under-desk heater be a fire risk?
- Any space heater poses a risk if misused. Keep yours at least 3 feet away from curtains, papers, fabric items, and flammable materials. Do not cover it or place it in an enclosed space. Choose models with automatic shut-off and tip-over protection, and never leave it running unattended for extended periods. If your heater lacks these safety features, it's worth replacing it with a newer, certified model.
- Does heater type—radiant versus convection—matter for energy use?
- Both types consume similar wattage, but radiant heaters are generally more efficient for personal use because they warm you directly through infrared radiation rather than heating the surrounding air. Convection models must raise room temperature more broadly, which takes longer and uses energy less effectively in a large or poorly insulated space. For an under-desk scenario, radiant models are the smarter choice for comfort with equivalent energy draw.