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Heated Blanket vs Space Heater: The Running Cost Math

A person at a desk wrapped in a heated throw with a small foot warmer underneath, beside a switched-off radiator, with a small wattage label on the throw's controller.
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Heating a person with a 100 watt throw costs 3 cents an hour. Heating the air with a 2000 watt space heater costs 60 cents. Do the math before you turn up the heat.

lucas

— 5 min read

A 100 watt heated throw costs 0.03 euros an hour to run, while a 2000 watt space heater draws 2 kilowatts and costs 0.60 euros for that same hour. This twentyfold difference is the starting point for anyone looking to stay warm without paying to heat empty space. When you heat an entire flat, you are paying to raise the temperature of thousands of cubic metres of air that you will never touch.

Central heating warms every corner of a room, but your body only occupies a tiny fraction of that volume. If you sit at a desk or on a sofa for five hours, you only need the immediate zone around you to be warm. The rest of the room can stay at 16 degrees.

Let's look at the actual numbers to see where the savings accumulate.

The arithmetic of domestic heat

Every plug-in heater has a power rating printed on its label. That number, measured in watts, determines your running cost. To find the hourly cost, divide the wattage by 1000 to get kilowatts, then multiply by your electricity tariff.

For these calculations, we will use a tariff of 0.30 euros per kilowatt-hour. This is a common rate for European households.

  • A 2000 watt fan heater draws 2.0 kilowatts. Running it for 5 hours a day costs 3.00 euros. Over a 30-day month, that is 90.00 euros.
  • A 100 watt heated throw draws 0.1 kilowatts. Running it for the same 5 hours costs 0.15 euros. Over a 30-day month, that is 4.50 euros.

The monthly saving is 85.50 euros per person.

This arithmetic is absolute. All standard electric heaters convert electricity to heat at 100 percent efficiency. A cheap heater and an expensive one drawing the same wattage will produce the exact same amount of heat. There is no special technology that bypasses this physics. The only way to pay less is to draw fewer watts.

Contact heating: the lowest-wattage options

The most efficient way to keep a person warm is to use contact devices that heat your body directly, rather than heating the air. Because the heat does not have to travel through the air, these devices draw very low power.

Let's compare the three primary options at our 0.30 euros per kilowatt-hour tariff:

  • A heated throw or blanket (100 watts) costs 0.03 euros per hour.
  • A foot warmer boot (50 watts) costs 0.015 euros per hour.
  • A heated seat pad (45 watts) costs 0.0135 euros per hour.

Cold feet are the primary reason people feel uncomfortable and turn up the central heating. A 50 watt foot warmer under your desk draws 0.4 kilowatt-hours over an 8-hour workday, costing 12 cents. A 2000 watt space heater running for that same workday draws 16 kilowatt-hours and costs 4.80 euros.

These contact devices do not raise the temperature of the room. If you step away from the desk or sofa, the room will feel cold. But while you are sitting down, they keep you warm for a fraction of the cost of any air heater.

Zoned space heaters: when you must heat the air

If you must heat the air in a room, for example, a bathroom before a shower or a single study where you work all day, you have to use a space heater. Warming air requires significant energy, which is why these devices draw between 1000 and 2000 watts.

You can keep the cost down by zoning, which means heating only the room you are using while leaving the rest of the flat cold.

Let's look at the three main types of space heaters:

  1. Oil-filled radiators (typically 1500 to 2500 watts). They take longer to warm up but continue to emit heat after they are turned off. They are best for spaces you occupy for several hours.
  2. Fan heaters (typically 2000 watts). They blow hot air instantly but the room cools down the moment you turn them off. They are suitable for short bursts of heat.
  3. Infrared panels (typically 300 to 600 watts for small under-desk units). They heat objects in their direct line of sight rather than warming the air.

If you use a 1500 watt oil-filled radiator to heat one small room instead of running a 10000 watt gas boiler for the whole flat, you save money. But if you run two or three space heaters in different rooms, you are drawing up to 6000 watts. At that point, running your central heating system is cheaper.

Here is the rule the math gives you: space heaters only save money if they allow you to keep your main central heating system turned off or set very low, and if you restrict their use to one room at a time.

The free actions that reduce heat loss

Before turning on any heater, stop the heat loss you already pay for.

  • Drafts. Sealing gaps around doors and windows with weatherstripping costs under 15 euros. It prevents cold air from entering and warm air from escaping.
  • Curtains. Closing heavy curtains at dusk keeps radiant heat from escaping through the window glass.
  • Doors. Keeping doors to unused rooms closed concentrates your heat in the space you are actually occupying.
  • Clothing. A heavy wool jumper, thermal underwear, and thick socks let you sit comfortably in a room that is 16 degrees instead of 20 degrees.

Lowering your thermostat by just 1 degree can reduce your heating bill by up to 10 percent. These steps cost next to nothing but they directly reduce the workload of any heater you run.

Standard safety rules for electric heating

Mixing electricity, heat, and fabrics requires strict safety habits.

  • Inspect cords. Look for worn insulation, loose connections, or scorch marks on electric blankets. Never fold them tightly while they are hot, as this damages the internal heating elements.
  • Plug directly into wall sockets. High-draw heaters must go straight into a wall outlet. Thin extension cords and multi-way adapters can easily overheat and start fires.
  • Keep clear. Maintain at least one metre of clear space around any space heater. Keep them away from curtains, bedding, and furniture.
  • Do not leave unattended. Turn off space heaters when you leave the room or go to sleep. Do not use them to dry wet clothes draped directly over the unit.

These safety habits ensure your cheap warmth does not become a hazard.

The heating budget model

Here is the rule to guide your winter heating: buy a 100 watt heated throw for your desk or sofa, keep your thermostat at 16 degrees, and only turn on a space heater when you need to warm a single room for less than two hours. Every hour you heat the person instead of the room keeps money in your pocket.

This article is independent analysis by House of Agile. It reflects general physics and public energy-efficiency guidance, not professional electrical, safety, or financial advice. Running costs depend on your own electricity tariff and usage, and appliance safety depends on the specific product and its condition. Verify the wattage, safety certification, and instructions of any specific device, and follow local electrical safety guidance, before buying or using it.

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