Tariffs

Bills higher after heat pump install

Warning Do not attempt any electrical or gas work yourself. Always use a qualified, MCS-certified, or Gas Safe registered professional for repairs.

What you’re seeing (symptoms)

Your monthly direct debit has increased, or your electricity usage has spiked significantly more than your gas usage has dropped since the installation.

What’s normal vs not normal

Normal:

  • Electricity usage being 3–4 times higher than before (since you are now using it for heating).
  • Higher bills in the first month as you (and the heat pump) learn the best settings.
  • A total energy bill that is roughly the same as before, but shifted entirely to electricity.

Not normal:

  • Monthly bills doubling or tripling compared to your old gas + electric combined total.
  • The heat pump’s “Immersion Heater” or “Backup Heater” running constantly.

Likely causes (ranked)

  1. Wrong Tariff: You are still on a “standard” flat-rate electricity tariff instead of a “Heat Pump” or “Time of Use” tariff.
  2. Usage Habits: Trying to run the heat pump like a gas boiler (2 hours in the morning, 4 hours at night) instead of “low and slow.”
  3. Low Efficiency (COP): The system is running at a very high flow temperature (e.g., 55°C) which is expensive.
  4. Immersion Backup: The domestic hot water is being heated by the electric immersion heater rather than the heat pump.
  5. Poor Insulation: Your home is losing heat faster than the heat pump can efficiently replace it.

Quick checks you can do safely

  • Check your electricity bill—what is your price per kWh?
  • Check your heat pump controller—is there an “Electric Heater” or “Boost” light constantly on?
  • Compare your current COP (Coefficient of Performance) on the unit’s display (it should be above 3.0).

When to call an installer

  • If your seasonal COP is below 2.5.
  • If the backup heater is running even when it’s not freezing outside.
  • If you suspect the system wasn’t “commissioned” correctly (e.g., the weather compensation curve is too steep).

Questions to ask your installer

  • “Can we lower the flow temperature to improve efficiency?”
  • “Is the hot water cylinder sensor positioned correctly?”
  • “Are there any settings we can optimize for my specific electricity tariff?”

Related NetZeroNow tools & guides

FAQs

Is electricity more expensive than gas? Yes, per unit (kWh), electricity is usually 3–4 times the price of gas. This is why a heat pump MUST be 3–4 times more efficient than a boiler to break even on cost.

What is a ‘Heat Pump Tariff’? Tariffs like ‘Octopus Cosy’ offer cheaper windows of electricity during the day and night specifically to allow you to run your heat pump for less.

Should I use ‘Boost’ for hot water? Only when absolutely necessary. Using the ‘Boost’ button usually turns on a standard electric heater, which is much more expensive than using the heat pump.

Does a heat pump save money? With current UK energy prices, a well-installed heat pump on a good tariff should cost roughly the same or slightly less to run than a modern gas boiler.

Why is my ‘Standing Charge’ so high? Standing charges are a fixed daily cost and haven’t changed much because of the heat pump, but you may be able to save by removing your gas meter and its associated standing charge.

Written by NetZeroNow | Last updated on 2026-03-02