Heating Cost Calculator
What heating a home costs for the season, and what insulation and a lower thermostat would save.
Heating is the largest energy cost in most homes and the one where small changes move the bill most: a degree off the thermostat, one more layer of insulation, or a more efficient boiler all reduce the same demand.
Enter the size of the home, how well insulated it is, what you pay for energy and what temperature you keep it at, and this calculator estimates the cost of the season and what improving each factor would save.
At a glance
- What you enter
- Heated floor area, Insulation, Climate, Indoor temperature, Energy need at 18 degrees and average insulation, Heating system efficiency, Price per kWh of energy, Length of the heating season, Temperature reduction to test
- What you get
- Heating cost for the season, Heating cost per month, Saving from the lower setting, Cost at the lower setting
- Formula shown
- Yes - every step, right below your results.
- Cost and privacy
- Free, no account needed, and nothing you type is stored.
See worked examples ↓ Read the FAQ ↓ Share this calculator ↓
Results are estimates for general information only - always verify with a professional or official source before acting on them.
How to use the Heating Cost Calculator
- 1 Enter Heated floor area (square metres)
- 2 Enter Insulation
- 3 Enter Climate
- 4 Enter Indoor temperature (degrees)
- 5 Enter Energy need at 18 degrees and average insulation (kWh per square metre per season) - Around 90 is typical for an older home in an average climate; 50 or less for a well-insulated modern one.
- 6 Enter Heating system efficiency
- 7 Enter Price per kWh of energy
- 8 Enter Length of the heating season (months)
- 9 Enter Temperature reduction to test (degrees)
- 10 Press Calculate. You get Heating cost for the season, Heating cost per month, Saving from the lower setting, Cost at the lower setting, and every intermediate step stays visible under “How is this calculated?”
- 11 Change one number at a time to see what moves the result - that is usually the most useful thing a calculator can tell you.
Worked examples
Real numbers run through this calculator. Open any example to load it into the form above and change it.
A poorly insulated 140 square metre house in a cold winter
Single glazing, 21 degrees indoors, an 80% efficient boiler and 9 cents per kWh.
You enter
- Heated floor area
- 140 square metres
- Insulation
- 1.4
- Climate
- 1.3
- Indoor temperature
- 21 degrees
- Energy need at 18 degrees and average insulation
- 90 kWh per square metre per season
- Heating system efficiency
- 80%
- Price per kWh of energy
- $0.09
- Length of the heating season
- 6 months
- Temperature reduction to test
- 1 degrees
You get
- Heating cost for the season
- $3,160.32
- Heating cost per month
- $526.72
- Saving from the lower setting
- $193.49
- Cost at the lower setting
- $2,966.83
At 21 degrees the temperature factor is 1.225, so the home needs 200.66 kWh per square metre and 28,092 kWh of heat for the season. At 80% efficiency that is 35,115 kWh of energy bought, costing $3,160.32, or $526.72 a month across a six-month season and $22.57 per square metre. Turning the thermostat down to 20 degrees would cut the factor to 1.15 and save about $193.49 over the season, taking the bill to $2,966.83, which is 6.1% of it.
A well-insulated 100 square metre home with a modern boiler
Excellent insulation, an average winter, 20 degrees indoors, a 92% efficient boiler and 10 cents per kWh.
You enter
- Heated floor area
- 100 square metres
- Insulation
- 0.5
- Climate
- 1
- Indoor temperature
- 20 degrees
- Energy need at 18 degrees and average insulation
- 50 kWh per square metre per season
- Heating system efficiency
- 92%
- Price per kWh of energy
- $0.10
- Length of the heating season
- 5 months
- Temperature reduction to test
- 2 degrees
You get
- Heating cost for the season
- $312.50
- Heating cost per month
- $62.50
- Saving from the lower setting
- $40.76
- Cost at the lower setting
- $271.74
The temperature factor at 20 degrees is 1.15, so the demand is 28.75 kWh per square metre and 2,875 kWh of heat for the season. At 92% efficiency that is 3,125 kWh of energy bought, costing $312.50, or $62.50 a month across five months and $3.13 per square metre, about 14% of the poorly insulated house per square metre. Dropping two degrees to 18 brings the factor to 1.0 and saves $40.76 over the season, which is 13.0% of the bill.
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Frequently asked questions
What is base demand, and where do I get a figure?
Base demand is the heat a home needs for a season, in kilowatt hours per square metre, assuming average insulation, an average climate and a room kept at 18 degrees. Around 90 suits an older home that has not been insulated; 50 or less suits a well-insulated modern one.
You can also work backwards from a real bill: take the energy you bought, multiply by the system efficiency to get the heat delivered, then divide by the floor area and by the temperature, insulation and climate factors that applied. That gives your own base demand, which is more accurate than any table.
How does the indoor temperature change the estimate?
Temperature enters as a factor: 0.55 plus 0.075 for every degree above 12. At 18 degrees the factor is 1.0, at 20 degrees it is 1.15, and at 22 degrees it is 1.30. The factor stands for the growing difference between inside and outside, which is what drives heat loss.
Test a reduction in the last field and the calculator applies the same factor at the lower setting, so the money attached to one degree is visible. The setting cannot fall below 12 degrees, which is where the model starts.
Is this the same as a heat loss survey?
No. A survey measures the actual building: the area of every wall, roof, window and floor, their insulation values, air tightness and the local design temperature. This page applies a shaped estimate to the floor area and two factors, so it is a comparison tool rather than a prediction of your next bill.
Use it to rank options. The gap between poor and excellent insulation, or between one degree and two, is a reliable signal even when the absolute figure is not, and that comparison is usually the decision you are trying to make.
What does system efficiency mean?
It is the share of the energy you buy that ends up as heat in the room. A modern condensing boiler is around 90%, an older non-condensing one 70 to 80, and an open fire considerably less. The heat demand is divided by that percentage to get the energy purchased, which is what you pay for.
A heat pump works differently: it moves heat rather than creating it and can deliver several units of heat per unit of electricity, so its efficiency is above 100% and this field cannot represent it properly. For a heat pump, compare the metered running cost of the two systems directly instead.