Skip to content

CALCULATOR · Finance

Gas Heating Cost Calculator

What it costs to keep your home warm — heat load, gas use and the daily, monthly and seasonal bill.

Show formula
heat load = volume × heat loss factor × (indoor − outdoor) · energy = heat load × hours ÷ 1000 · purchased = energy ÷ boiler efficiency · cost = purchased × price per kWh · month = day cost × days

Inputs

Heated floor area — a studio is about 25 m², a family flat 60–90 m², a detached house 120–250 m².

2.5

Floor-to-ceiling height — most homes sit at 2.4–2.7 m; double-height halls can reach twice that.

—

How readily the building dumps heat, in W per m³ per degree: about 0.5 for a modern well-insulated home, 0.9 for an average one, 1.4+ for an old uninsulated house.

20

The thermostat setting — most homes sit at 18–22 °C.

-5

The outdoor cold the estimate should assume — 0–5 °C is a mild winter day, −10 to −20 a cold snap.

12

How many hours a day the home is actually kept warm — all-day heating is 16–24 h, morning-and-evening heating 8–12 h.

—

A modern condensing gas boiler is 90–96%, an older non-condensing one 70–80%. Combustion never exceeds 100%.

What one kWh of gas costs on your bill. A meter reading in m³ or therms converts first: 1 m³ ≈ 10.5 kWh, 1 therm = 29.3 kWh.

—

How many days that month the heating actually runs — 30 is every day.

Result

Your result appears here

Enter Floor area and the result fills in as you type.

How it works

  1. Enter the heated floor area and ceiling height, then the heat loss factor that stands in for the building — about 0.5 for a modern well-insulated home, 0.9 for an average one, 1.4 or more for an old uninsulated house.
  2. Add the two temperatures — the thermostat setting and the outdoor cold the estimate should assume — and how many hours a day the home is actually kept warm.
  3. Enter the boiler efficiency — 90–96% for a modern condensing boiler, 70–80% for an older one — and your price per kWh from the gas bill to get the day, month and cold-snapshot yearly cost.

Frequently asked questions

What does the heat loss factor actually describe?

How readily the building dumps heat: every cubic meter of space loses a fixed share of the indoor–outdoor temperature gap each hour. A passive-grade shell sits near 0.5 watts per cubic meter per degree, average construction near 0.9, and an old uninsulated house at 1.4 or more. If you are unsure, start at 0.9 and compare the result with a real bill — the direction of the correction tells you your home’s true factor.

My gas meter measures cubic meters or therms — how do I use it?

Convert the price first: one cubic meter of natural gas holds roughly 10.5 kWh, and one therm is 29.3 kWh. A tariff of 0.90 per m³ works out near 0.086 per kWh — enter that figure and the rest of the maths is identical.

Is the yearly figure my real annual bill?

No — it holds the outdoor temperature and heating hours fixed for twelve months, so it is a cold-snapshot rate, not a seasonal total. Real bills come in lower because mild days need less and the heating season eventually ends. Treat the monthly figure as the deep-winter rate and the per-square-meter figure as the honest way to compare one home with another.

Examples

An 80 m² flat with 2.5 m ceilings and average insulation (factor 0.9), held at 20 °C while it is −5 °C outside, 12 hours a day on a 90%-efficient boiler at 0.10 per kWh
4.5 kW of heat load, 60 kWh from the meter a day — 6.00 a day, 180.00 a month.
A 120 m² uninsulated house (factor 1.4) held at 20 °C at 0 °C outside, 12 hours a day on an 80% boiler at 0.09 per kWh
8.4 kW of heat load, 126 kWh from the meter a day — 11.34 a day, 340.20 a month.

Related calculators