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What does it cost to heat a home office all day?

Work out what a room actually loses in heat, the heater size it needs, and what holding it at a comfortable temperature costs per hour, per month and across a winter.

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Using the Greek average of 23.81c/kWh — Eurostat, the second half of 2025.

Small, but heated through the whole working day rather than an evening — which is the part that adds up.

The room
m²
Length times width. A typical UK living room is around 16 m²; a double bedroom around 12 m².
m
2.4 m (8 ft) in most modern homes. Victorian rooms are often 3 m or more, which is a fifth more air to heat.
Only walls facing outdoors count. A wall shared with a heated room, or with a neighbour's heated room, loses almost nothing.
m²
Total glazing, frames included. A standard domestic window is roughly 1.2 × 1.2 m, so about 1.5 m².
A ceiling under a heated bedroom loses nothing. A ceiling under a cold loft is often the biggest single loss in the room.
How it is built
Describes the construction, not the era — the same wall was normal in different decades in different countries. The exact U-values behind each option are listed in the assumptions below.
Heating it
°C
18 to 21 °C covers most people. Every degree costs roughly 7 to 10% more, because it widens the gap the heat has to bridge.
°C
Defaults to the average outdoor temperature on days your country needs heating at all. Drop it to freezing to see a cold snap.
%
100 for any plug-in electric heater — fan, oil-filled, panel, halogen or infrared, all identical on this measure. Use 300 to 400 for an air-to-air heat pump or an air conditioner running in heat mode.
hours
Time the heater is actually delivering heat. A thermostat cycling on and off counts only the time it is on.
c/kWh
From your bill, per kilowatt hour. Defaults to the current published figure for your country.
Cost for a winter €36.08
Heat this room loses 115
Heater size needed (kW) 0.5
Cost per hour €0.03
Cost per day €0.25
Cost per month €7.47
Electricity per day 1 kWh
Heat loss per degree (W/K) 12.1

Common cases

What drives the cost

A home office inverts the usual pattern. The room is small, often internal, and frequently has only one external wall — all of which make its heat loss modest. What makes it expensive is duration: nine hours a day, five days a week, through the coldest part of the day, in a room that would previously have sat empty and unheated while everyone was out. Working from home genuinely does raise a heating bill, and this is where it comes from.

It is also the room where heating the person rather than the space pays off most, because you are stationary in one spot for hours. A heated chair pad or a small under-desk panel draws 50 to 150 watts against the several hundred the room needs, and at that scale the comparison is not close. Warm the room enough to keep surfaces above the dew point, and warm yourself the rest of the way.

How this is worked out

A room loses heat through every surface facing somewhere colder, and through the air that leaks out and has to be warmed again. Each surface loses in proportion to its area, how well it insulates, and how much colder it is outside. Add those together and you get a heat loss coefficient — watts per degree — which belongs to the room alone and does not change with the weather. Multiply it by the temperature difference you want to hold and you have the heat the room needs. For a plug-in electric heater that is exactly the electricity it draws, because a resistive heater turns all of its electricity into heat. Nothing about this is brand-specific: a £15 fan heater and a £300 designer panel of the same wattage cost precisely the same to run.

What this assumes

  • U-values for walls, roofs and windows are the published defaults from BRE's RdSAP 10 specification (February 2024) and consultation paper CONSP:16. Those are in-situ measured figures — the solid-brick default was cut from 2.1 to 1.7 W/m²K after fieldwork found real walls beat the theoretical calculation. The five options above use, in order: walls 1.7, 1.5, 0.7, 0.30 and 0.18; windows 4.8, 2.8, 2.0, 2.0 and 1.4; roofs 0.68, 0.40, 0.16, 0.16 and 0.11.
  • Floor U-values (0.7, 0.7, 0.45, 0.22, 0.13) and air change rates (1.2, 1.0, 0.7, 0.55, 0.4 per hour) are representative rather than measured. A real floor depends on the ratio of exposed perimeter to area, and real air leakage depends on chimneys, flues and how sheltered the building is — neither is knowable from the questions above, and both are the largest source of uncertainty here.
  • The room is assumed square. A long thin room of the same floor area has more external wall and so loses more: 2 × 8 m has a 20 m perimeter against 16 m for 4 × 4 m, and this would under-read it by roughly a quarter.
  • Only surfaces facing unheated space are counted. Walls to a heated neighbour, and ceilings under heated rooms, are treated as losing nothing — close enough in practice, though a wall to a neighbour who never puts the heating on is not.
  • Nothing is credited for heat you get free. People, cooking, lighting, appliances and winter sun through a south-facing window all add real warmth — often 200 to 400 W in an occupied living room — so a real bill usually lands below the figure here.
  • The seasonal figure multiplies the daily cost by the number of days a year your country needs heating at all, at the average outdoor temperature for those days. It is a fair estimate of a whole winter, not a prediction of any particular one.
  • The rate filled in for you is an average that spreads fixed charges across a year's usage, so it sits above what one extra unit really costs. Entering the unit rate from your own bill gives a closer answer.

Questions

How much does working from home add to heating costs?

For a typical small office room, the figure above across a winter — usually somewhere between a modest and a noticeable share of the annual heating bill, depending on the climate and how well the room is built. It is the hours that do it rather than the room: the same room heated only in the evening would cost a fraction of it.

Is a small heater in one room cheaper than the central heating?

For one occupied room, usually yes. Central heating warms the whole house including rooms nobody is in, and the boiler and pipework lose something on the way. A single plug-in heater puts all its energy into the one room that needs it. The picture reverses as soon as two or three rooms are occupied, since electricity generally costs several times more per kilowatt hour than gas.

Are some electric heaters cheaper to run than others?

No. Every plug-in electric heater is 100% efficient at the point of use — fan, oil-filled, convector, panel, halogen and infrared alike. A 2 kW heater of any type uses 2 kWh an hour and costs the same. What differs is how the heat feels and how quickly it arrives: infrared warms objects and people directly so it can feel effective sooner, and an oil-filled radiator keeps releasing heat after it switches off. Neither changes the meter reading. Anything advertised as a cheap-to-run electric heater is either a heat pump or a claim worth ignoring.

Is it cheaper to leave the heating on low all day?

No, and the physics above is why. A room loses heat in proportion to how much warmer it is than outside, so a room kept warm all day spends every one of those hours losing heat. Letting it cool means a smaller temperature difference for most of the day and therefore less total loss. Reheating costs something, but less than the standing loss it avoids. The exception is a home so damp that letting it go cold invites condensation, which is a different problem with a different fix.

Why is my conservatory so expensive to heat?

Because almost all of it faces outside. Glass loses heat several times faster than an insulated wall, a conservatory usually has three glazed walls plus a glazed or thin roof, and its floor sits over cold ground. Put a conservatory's numbers in above and the heat loss often comes out three or four times a normal room of the same size. The honest answer is usually to heat it only when it is in use, and to accept it as a spring and autumn room.

Should I heat one room instead of the whole house?

Often yes, if the rest of the house genuinely stays unheated and you accept it being cold. Heating one room costs roughly what this calculator says; heating a whole house costs the same arithmetic repeated for every room, plus the corridors between them. The catch is that unheated rooms get cold surfaces, and cold surfaces attract condensation and then mould. If you go down this route, ventilate the cold rooms rather than sealing them up.

How much does turning the thermostat down by one degree save?

Roughly 7 to 10% of the heating bill for that room, and you can see it in the maths: cost is proportional to the gap between inside and outside. Holding 20 °C against 8 °C is a 12-degree gap; holding 19 °C is 11 degrees, which is 8% less. The saving is bigger in a mild climate, because one degree is a larger share of a smaller gap — which is also why the same advice is worth more in Portugal than in Finland.

Is an air-to-air heat pump worth it for one room?

On running cost, usually yes and by a lot. A heat pump does not make heat, it moves it, so it delivers three to four units of heat per unit of electricity — set efficiency to 350 above and the bill falls by about two thirds. Against that sits the installation cost, which is thousands rather than tens, so the sum turns on how many hours a year you actually heat that room. A room heated all winter pays it back; a spare bedroom heated at Christmas does not.

Related tools

Sources

Rates from Eurostat for the second half of 2025. Last reviewed August 27, 2026.