Is Switching Worth It? Savings and Payback Calculator

Defaults last checked: October 29, 2026. Results are estimates.

“It’s more efficient” is not the same as “it’s worth it.” A new appliance or heating system only pays off if the yearly saving covers what you spend on it within a time you’re comfortable with. This calculator puts those two numbers side by side.

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How to use it

  1. Choose your country. This fills in the electricity price, and gas price where we have one, from public data.
  2. Pick a comparison. “Old fridge → efficient fridge” and “Gas boiler → heat pump” load sensible starting figures. “Custom comparison” leaves the energy use for you to enter.
  3. Enter energy use per year for both options. For appliances, the energy label or the manufacturer’s spec sheet gives kWh per year. For heating, your bills show kWh, therms or cubic meters (convert to kWh first).
  4. Add the upfront cost and any grant. If you would have to replace the old one anyway, enter only the extra you pay for the efficient model.

The results update as you type.

The formula

  • Yearly cost now = current energy use (kWh) × current price per kWh
  • Yearly cost after = new energy use (kWh) × new price per kWh
  • Yearly saving = cost now − cost after
  • Simple payback = (upfront cost − grant) ÷ yearly saving
  • Result over 10 years = yearly saving × 10 − (upfront cost − grant)

Two different prices are allowed because a switch often changes fuel, for example from gas to electricity.

Worked example 1: replacing an average US fridge

The U.S. Department of Energy puts the average refrigerator-freezer in American homes at 588 kWh a year. Its federal buying guidance lists an ENERGY STAR 18-cubic-foot top-freezer model at 363.5 kWh a year. At the EIA’s August 2026 U.S. average residential price of 18.16 cents per kWh:

  • Old fridge: 588 × $0.1816 = $106.78 a year
  • New fridge: 363.5 × $0.1816 = $66.01 a year
  • Saving: $40.77 a year

If the efficient model costs $400 more than the cheapest replacement, payback is about 9.8 years. If your old fridge still works, that’s a slow return. If it’s dying anyway, the efficient one is an easy choice.

Worked example 2: gas boiler to heat pump (UK)

Ofgem’s typical medium household uses 9,500 kWh of gas a year (the value used from July 2026). At the October–December 2026 price cap gas rate of 7.97p per kWh, that’s £757 a year before the standing charge.

With a 90% efficient boiler, that gas delivers about 8,550 kWh of heat. A heat pump with a seasonal efficiency (SCOP) of 2.8, the median measured across 291 air source heat pumps in the UK government-funded Electrification of Heat trial, needs about 3,054 kWh of electricity. At the cap rate of 26.32p, that’s £804 a year, so about £47 more on a standard tariff.

At a SCOP of 3.5 the same home needs about 2,443 kWh, or £643 a year, a saving of about £114. If you also disconnect from gas, you stop paying the gas standing charge, which is 29.68p a day (about £108 a year) under the current cap. That figure isn’t in the calculator, so add it yourself if it applies.

This is why installation quality matters so much. For the full picture, see our guide to heat pump running costs vs gas and what the Boiler Upgrade Scheme covers.

What the result doesn’t tell you

  • Prices change. The calculator holds today’s prices flat for every year.
  • Standing charges, servicing and repairs are left out. A heat pump replaces boiler servicing with its own. A new fridge may come with a longer warranty.
  • Comfort and other benefits. Cooling, quieter running or a smaller carbon footprint have value that doesn’t show up in payback.
  • Money has a time cost. Simple payback ignores interest. If you borrow to pay for the switch, include the finance cost in the upfront figure.

Compare supplier tariffs

In the UK and Australia, pick your region and the calculator ranks the tariffs we could verify on each supplier’s own price sheet, each with its source. “Use this rate” copies a unit rate into the calculator. In London, Flexible Octopus is 26.60p/kWh plus 41.39p/day; British Gas, EDF and E.ON Next are 26.60p/kWh plus 42.91p/day. The price cap keeps standard tariffs close, so near-ties are normal.

FAQ

What counts as a good payback time?

That depends on how long the new item lasts. A rough test: if payback is well inside the expected lifetime, the switch makes financial sense. If payback is longer than the lifetime, it doesn’t, at least on energy cost alone. For reference, the U.S. Department of Energy assumes a refrigerator lasts about 16 years in its cost analysis. Check the warranty and expected life for anything else you’re comparing.

Should I replace something that still works?

Run the numbers with the full price of the new item. If the payback is long, it’s usually better to wait until the old one fails and then buy the efficient model.

Where do I find my energy use per year?

On the energy label, in the product manual, or by measuring with a plug-in energy meter for a week and multiplying up. For heating, use a full year of bills.

Why is my heat pump result negative?

Because electricity costs about 3.3 times as much as gas per kWh in Britain right now. A heat pump needs a SCOP above about 3 just to match a 90% efficient boiler on unit cost. A heat pump tariff or a better installation can change that.

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