Energy & Home Calculators
13 free calculators · Updated for 2026/27
Household energy is one of the few bills where a change of tariff or a piece of equipment shows up directly in pounds. Energy calculators estimate gas, electricity and water costs, price the running cost of individual appliances, and work out payback periods for solar panels, heat pumps, new boilers, glazing and lighting, which is what is needed before signing up to a tariff or paying for an installation.
Annual gas and electricity costs come from the Energy Bill Calculator, which uses Ofgem price cap rates and breaks the total down to a monthly figure. The Solar Panel Savings Calculator answers how long panels take to pay for themselves, the Heat Pump Running Cost Calculator sets a heat pump against a gas or oil boiler, and the Standing Charge Savings Calculator isolates what you pay before using any energy at all. Single devices are priced by the Electricity Cost Calculator (per appliance).
Energy Bill Calculator
TrendingEstimate your annual gas and electricity bills using Ofgem price cap rates. See monthly and daily costs.
EPC Rating Improvement Calculator
TrendingEstimate your EPC rating and see which upgrades will improve it most. Includes costs and annual savings.
Solar Panel Savings Calculator
Calculate solar panel payback period, annual savings and 25-year return on investment.
Heat Pump Running Cost Calculator
TrendingCompare heat pump vs gas/oil boiler running costs. Calculate payback period and annual savings.
Electricity Cost Calculator (per appliance)
Calculate how much an appliance costs to run per day, week, month and year. Quick-select from common appliances.
LED Bulb Savings Calculator
Calculate how much you save by switching from old bulbs to LED. See payback period and annual savings.
Water Bill Calculator
Estimate your annual water bill for metered or unmetered supply including sewerage charges.
Boiler Replacement Cost Calculator
Compare old vs new boiler efficiency. Calculate installation cost, annual savings and payback period.
Double Glazing Savings Calculator
Calculate double glazing costs and annual energy savings by house type. See payback period.
Smart Meter / Appliance Cost Calculator
Work out what each appliance costs to run per day at your electricity unit rate, the breakdown a smart meter display shows, and where the savings are.
EPC Band Comparison Calculator
Compare energy costs between EPC bands. See annual savings from upgrading your rating.
Standing Charge Savings Calculator
Calculate how much you pay in standing charges alone. Compare zero standing charge tariffs.
Gas Cost Calculator
Calculate annual gas bill from kWh usage, unit rate and standing charge.