Why is my energy bill so high? Start with the building

Most advice about high bills starts with tariffs. Tariffs change the price of a unit. The building decides how many units you need, and that is usually where the money goes.

2 March 2026 7 min read

Where the energy goes in a typical home

In most UK homes, space heating is the single largest use, followed by hot water, with appliances, lighting and cooking making up the rest. That order matters, because it means the biggest savings come from needing less heat rather than from swapping bulbs.

The five usual suspects

  1. 1Uninsulated or poorly insulated walls, especially solid walls in pre 1919 homes.
  2. 2Thin or compressed loft insulation, or a loft that has been boarded over the top of it.
  3. 3An old, oversized or badly controlled boiler running at a high flow temperature.
  4. 4No room thermostat, or heating that runs to a timer with every radiator wide open.
  5. 5Draughts. Individually small, collectively significant, and cheap to fix.

Fuel type changes everything

HeatingTypical position on running cost
Mains gas boilerThe benchmark most homes are compared against
Heat pumpEfficient, but sensitive to insulation and system design
Oil or LPGOff grid, price volatile, storage to maintain
Electric storage heatersOften expensive unless on a suitable time of use tariff
Direct electric panel heatersUsually the most expensive way to heat a whole house

If a property is off the gas grid, the certificate and the bills will look different from a neighbouring town, and that is worth knowing before you buy rather than after your first winter.

Quick diagnostics you can do this week

  • Read the energy certificate and note every element rated poor or very poor.
  • Check the loft with a tape measure. Anything under 200mm is a top up candidate.
  • Turn the boiler flow temperature down if you have a condensing combi and radiators that run scaldingly hot.
  • Close the curtains at dusk and fit draught excluders on external doors.
  • Take a meter reading weekly for a month so you know your baseline instead of guessing.

When the answer is not the building

Estimated bills, an old faulty meter, an immersion heater left on, a fault in an electric shower circuit, or a hot water cylinder heating continuously can all produce a bill that does not match the house. If your usage jumped without a change in behaviour or weather, check the meter and the cylinder before you spend money on insulation.

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