United Kingdom version
How it works
Put electricity and the comparison fuel on the same delivered-heat basis instead of comparing unlike fuel units.
This is the United Kingdom planning view, with monetary inputs and outputs in GBP. A currency label does not establish that a tax rate, construction price, coverage rule or legal limit has been verified locally. The inputs and limitations below describe the actual scope.
Input query strings and outputs
Use an input name in this page’s URL as ?name=value, and join additional inputs with &. Portable shared links may instead use the compact ?ac= state parameter.
Input query strings
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?usefulHeat=Annual useful heat required, kWhNumber · Required · Default: 18,000
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?heatPumpCop=Seasonal heat-pump coefficient of performanceNumber · Required · Default: 3
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?fuelEfficiency=Seasonal comparison-heater efficiencyPercentage · Required · Default: 90
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?electricityRate=Electricity price per input kWhMoney · Required · Default: 0.2
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?fuelRate=Comparison fuel price per input kWhMoney · Required · Default: 0.08
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?electricFixed=Annual additional electric fixed chargesMoney · Required · Default: 0
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?fuelFixed=Annual fuel fixed chargesMoney · Required · Default: 120
Outputs
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heatPumpEnergyHeat-pump input electricity, kWhNumber
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fuelEnergyComparison fuel input, kWhNumber
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heatPumpCostHeat-pump annual costCurrency · Currency: GBP
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fuelCostComparison heater annual costCurrency · Currency: GBP
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annualSavingHeat-pump annual savingCurrency · Primary output · Currency: GBP
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breakevenCopEnergy-only break-even COPNumber
Formula
input energy = useful heat ÷ seasonal efficiency; cost = input energy × unit price + fixed charges.
Calculations retain numeric precision internally. Displayed values are rounded for readability. Quantities that must be purchased as whole units are rounded up only where the formula explicitly requires it.
Read the inputs before calculating
- Annual useful heat required, kWh: Enter the quantity described by the label.
- Seasonal heat-pump coefficient of performance: Enter the quantity described by the label.
- Seasonal comparison-heater efficiency: Enter the quantity described by the label.
- Electricity price per input kWh: Enter the quantity described by the label.
- Comparison fuel price per input kWh: Enter the quantity described by the label.
- Annual additional electric fixed charges: Enter the quantity described by the label.
- Annual fuel fixed charges: Enter the quantity described by the label.
Reproducible worked example
The following is a fictional arithmetic example, not a local quote, a verified claimant or a market forecast. Its values are included so the formula can be checked. The form does not automatically confirm any verification checkbox.
| Input | Example value |
|---|---|
| Annual useful heat required, kWh | 18,000 |
| Seasonal heat-pump coefficient of performance | 3 |
| Seasonal comparison-heater efficiency | 90 |
| Electricity price per input kWh | 0.2 |
| Comparison fuel price per input kWh | 0.08 |
| Annual additional electric fixed charges | 0 |
| Annual fuel fixed charges | 120 |
| Output | Calculated result |
|---|---|
| Heat-pump input electricity, kWh | 6,000 |
| Comparison fuel input, kWh | 20,000 |
| Heat-pump annual cost | GBP 1,200 |
| Comparison heater annual cost | GBP 1,720 |
| Heat-pump annual saving | GBP 520 |
| Energy-only break-even COP | 2.25 |
Interpreting a changed assumption
Start with one complete scenario and change only one input when diagnosing a difference. Recheck units, the period of every rate, whether an amount is recurring or one-off, and whether a cost is already included elsewhere. A larger calculated benefit is not evidence that an assumption is more likely to occur.
Limitations
- Fuel must be priced per input kWh, not per gallon, therm, litre or cubic metre without a verified conversion. Seasonal COP is not a single mild-weather test value.
Frequently asked questions
What does this Heating Cost Comparison result represent?
Put electricity and the comparison fuel on the same delivered-heat basis instead of comparing unlike fuel units. It applies the displayed formula to your inputs; it does not infer omitted facts.
Are the starting amounts verified United Kingdom prices or legal rules?
No. Numeric defaults are illustrative unless an input or dated reference explicitly identifies a researched component. Currency is GBP; local quotes, eligibility and unsupported rules must be entered and verified separately.
What must I check before relying on the result?
Check the input units, supplier or authority evidence, the stated model exclusions and the period used for costs. This arithmetic does not supply missing site-specific design or local legal rules.
Can I compare or share different assumptions?
Change one assumption at a time and use the browser-local project or share controls. A shared URL contains the encoded input values; do not include information you do not wish to disclose.
Sources and reference scope
- DOE energy-use arithmetic — retrieved 2026-09-24. Energy consumption versus power; not a local tariff or an approval of this implementation.
- PVWatts: site-specific solar estimation — retrieved 2026-09-24. External site-yield model. AskCalculators uses your entered yield; it does not call or reproduce PVWatts.
- DOE insulation overview — retrieved 2026-09-24. Insulation and thermal resistance concepts; not structural or code approval.
These references support only their stated scope. They are not evidence that every local rule or price needed by the master expansion has been loaded.