Free Energy Tools and Calculators
Free, practical tools to help you understand energy bills, compare home-energy options and deal with your supplier. Choose a category below or start with the Energy Bill Calculator.
Looking for help with energy costs? See current grants and support schemes.
Bills and energy use
Work out what you use, what it costs and how your bill is built.
Energy Bill Calculator
Calculate a gas and electricity bill over any period using your rates, standing charges and usage.
Open tool →Electricity Bill Calculator
Calculate an electricity bill from your unit rate, standing charge and daily usage.
Open tool →Gas Bill Calculator
Calculate a gas bill from your unit rate, standing charge and daily usage.
Open tool →Standing Charge Calculator
See what your daily standing charges cost per week, month and year.
Open tool →Is My Energy Bill Normal?
Compare your annual bill with Ofgem's low, medium and high household consumption bands.
Open tool →Gas Meter Reading Calculator
Convert metric or imperial gas meter readings to kWh using the supplier formula.
Open tool →Appliance Electricity Cost Calculator
Calculate what a household appliance costs to run per day, week, month and year.
Open tool →Standby Power Calculator
Work out what always-on and standby devices cost each year.
Open tool →49 Day Rule Calculator
Find the date you can leave a fixed energy tariff without paying an exit fee.
Open tool →
Home heating and transport
Explore heat loss, heat-pump running costs and home EV charging.
Heat Loss Calculator
Estimate your home heat loss in kW and the indicative heat-pump size to investigate.
Open tool →Heat Pump Running Cost Calculator
Compare a heat pump with a gas boiler using your home and energy-price assumptions.
Open tool →EV Charging Cost Calculator
Work out the cost of charging an electric car at home per charge and per mile.
Open tool →
Solar and battery tools
Start with a quick estimate, assess a specific roof, explore battery economics and forecast generation.
Quick Solar Estimate
Estimate generation, bill savings and simple payback without entering an address.
Open tool →Solar Roof Calculator
Use a specific address and independent generation modelling to assess a roof and quote.
Open tool →Solar Battery Calculator
Model hourly solar, household demand and tariff rates to estimate battery savings.
Open tool →Solar Generation Forecast
Estimate how much an installed solar system could generate over the next seven days.
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Supplier help
Identify the right organisation and take the next practical step.
£100 Energy Payment Checker
Check whether your home qualifies for the £100 Household Energy Payment for council tax bands A to D in England, paid from January 2027, and whether you need to apply.
Open tool →Energy Complaint Letter Template
Generate a formal complaint letter to your energy supplier, covering overcharging, estimated bills, direct debits, switching and smart meters.
Open tool →Who Is My Energy Supplier?
A postcode cannot name your supplier. Find the part it does determine — your electricity region and network operator — and the two official services that name your supplier.
Open tool →
Frequently asked questions
Are these energy tools free to use?
Yes. Every tool on this page is free to use and does not require an account.
How accurate are the calculator results?
Results are estimates based on the figures you enter and the stated assumptions. Use rates and usage from a recent bill where possible, and treat property, solar and heating results as a starting point rather than a quote.
Which energy calculator should I use first?
Use the Energy Bill Calculator for an overall cost estimate. For solar, start with the Quick Solar Estimate, then use the Solar Roof Calculator if you want an address-specific assessment.
Do the tools store my personal information?
Most calculations run in your browser. Tools that need an address, postcode or live forecast send only the information needed to provide that result. Each tool explains its data use where you enter those details.
