Boiler Running Cost Calculator.
Estimate your boiler’s running costs with our free Boiler Running Cost Calculator. Enter your boiler size, efficiency, and gas price to get accurate hourly, daily, and monthly heating costs.
Estimate how much your boiler costs to run per hour, day, and month. Enter your boiler size, efficiency, and gas price to see accurate heating cost calculations.
A Boiler Running Cost Calculator helps you estimate the cost of running your gas boiler for heating and hot water. By entering your boiler’s kW size, efficiency percentage, daily usage, and your gas price per kWh, the calculator instantly shows your hourly, daily, and monthly running costs.
This tool is ideal for homeowners who want to understand their heating bills, compare the cost of different boiler sizes, or estimate savings when switching to a more efficient boiler.
Whether you have a combi boiler, system boiler, or regular boiler, this calculator gives you accurate, real-world cost estimates based on your actual energy usage and tariff.
With gas prices still fluctuating, knowing the actual cost of running your boiler is one of the most effective ways to manage your home heating costs and make smarter energy decisions.
How to Use the Boiler Running Cost Calculator
You only need a few details to get accurate boiler running cost results. Here’s how to use the tool:
1. Enter your boiler size in kW
Your boiler’s kW rating is shown on the boiler label or in the manual. Common sizes include 24kW, 28kW, and 30kW.
This value tells the calculator how much heat the boiler can produce.
2. Add your boiler efficiency (%)
Most modern condensing boilers are around 88–94% efficient, while older boilers may be lower.
Efficiency affects how much gas is converted into usable heat.
3. Type in your hours of use per day
For example:
- 4 hours/day in mild weather
- 6–8 hours/day in winter
4. Enter your gas price per kWh
Your gas tariff shows the price per kWh, usually between 7p and 10p depending on your supplier.
5. Click Calculate
The calculator immediately shows your boiler’s cost per hour, cost per day, and monthly running cost.
💡 Tip: If you’re unsure of your boiler efficiency, use 90% – it’s a realistic average for most UK homes.
Example Calculation – 24kW Combi Boiler
Here’s an example using a 24kW combi boiler, which is one of the most common boiler sizes in UK homes.
Example: Running Cost of a 24kW Combi Boiler
| Boiler Size | Efficiency | Hours/Day | Price per kWh | Cost per Day |
|---|---|---|---|---|
| 24kW Combi Boiler | 90% | 4 hours | 8p | £6.91 |
(Assuming gas price of 8p per kWh)
A 24kW boiler running for 4 hours per day with 90% efficiency costs approximately:
- £1.73 per hour
- £6.91 per day
- £207.36 per month (30 days)
This example shows how even small changes in efficiency or usage time can significantly affect your gas bill.
Understanding the Results of the Boiler Running Cost Calculator
The calculator provides three key insights about your boiler’s running cost:
Cost per hour
This shows how much it costs to run your boiler for 1 hour, based on its kW rating and efficiency.
Formula:
(Boiler kW × Efficiency %) × Gas price per kWh
Cost per day
This multiplies your hourly cost by the number of hours your heating runs each day.
Perfect for budgeting during the winter months.
Monthly cost
Your projected cost for a 30-day month.
This helps you estimate how much your heating contributes to your monthly gas bill.
Boiler efficiency impact
A higher-efficiency boiler turns more gas into usable heat.
For example:
- A 24kW boiler at 90% efficiency
- Uses far less gas than the same boiler running at 70%
Understanding these values helps you make informed decisions about heating usage, insulation improvements, and potential boiler replacements.
How to Reduce Your Boiler Running Costs
Energy prices are rising, but reducing your boiler costs doesn’t have to be difficult.
Here are practical tips to lower your gas usage and heating bills:
Lower your thermostat slightly
Reducing the temperature by 1°C can cut heating costs by around 10%, without a noticeable difference in comfort.
Use heating controls effectively
Smart thermostats, TRVs (thermostatic radiator valves), and programmable timers help you heat only the rooms you use, and only when needed.
Improve insulation
Loft insulation, cavity wall insulation, and draught-proofing dramatically reduce heat loss, meaning your boiler runs less often.
Service your boiler yearly
A well-maintained boiler performs more efficiently, burns less gas, and runs more safely.
Consider upgrading an older boiler
Modern condensing boilers use far less gas than older non-condensing models.
The savings over time often justify the upgrade, especially if your boiler is 12+ years old.
Frequently Asked Questions (FAQ)
How much does it cost to run a 24kW boiler?
A typical 24kW combi boiler costs around £1.60–£2.00 per hour, depending on efficiency and your gas price per kWh.
Does boiler size affect running cost?
Yes. Larger boilers burn more gas because they produce more heat, so a 30kW boiler is more expensive to run than a 24kW boiler for the same amount of time.
Is it cheaper to leave the heating on low all day?
No. It generally costs more. It’s usually more efficient (and cheaper) to heat your home only when needed using timers and thermostats.
How can I make my boiler run more cheaply?
Improve insulation, set your thermostat slightly lower, use TRVs, and ensure your boiler is serviced annually for maximum efficiency.
What’s the average gas price per kWh?
Most UK households pay between 7p and 10p per kWh, depending on their supplier and tariff.