An unexpectedly large electricity figure can be real and still tell you very little about the cause.
Before changing the heat pump, establish what the number actually represents.
1. Is it whole-house electricity or heat-pump electricity?
A whole-house smart meter can include:
- cooking;
- lighting;
- laundry;
- tumble drying;
- EV charging;
- electric showers;
- portable heaters;
- the heat pump;
- everything else using electricity.
Do not attribute every kilowatt-hour to the heat pump because it is the largest new appliance.
If your system also reports heat-pump electricity or heat delivered, keep those figures separate.
2. Electricity in is not the same as heat out
A heat pump uses electricity to move heat into the home.
That means useful heat delivered can be greater than electrical input.
COP describes the relationship between heat output and electricity input at a particular operating condition. Seasonal performance covers a wider period.
An instantaneous COP number should not be treated as a score. Outdoor temperature, heating-water temperature, domestic hot water, recovery, and defrost all affect the operating condition.
3. Compare periods that mean something
“Monday used 30 kWh and Tuesday used 42 kWh” is weak evidence without context.
Ask what changed.
A useful investigation works through these categories:
- weather;
- comfort target;
- recovery after setback;
- hot-water demand;
- auxiliary or backup heating;
- settings changes;
- other household electrical loads;
- faults or genuine system problems.
Weather
As outdoor temperature falls, the building generally loses heat faster and needs more energy to maintain the same indoor temperature.
The heat pump may also be working across a larger temperature difference, particularly when producing warmer water.
Higher use in genuinely colder weather is not automatically evidence of poor operation.
Indoor target and setback recovery
Check whether the home was being maintained warmer than usual.
Also ask whether the system was recovering after:
- a deep overnight setback;
- holiday mode;
- a power interruption;
- a long heating-off period.
A large setback can create a demanding recovery period. That does not prove the schedule is wrong, but it is a useful variable to test before changing several technical settings.
Domestic hot water
Space heating and domestic hot water are different jobs.
A high-use day may also have included:
- more showers;
- baths;
- guests;
- a manual boost;
- a hygiene or disinfection cycle.
Do not assume every heat-pump kilowatt-hour went into room heating.
Auxiliary or backup heating
If the controller indicates a backup, booster, immersion, or direct-electric heater, record:
- when it appears;
- how long it appears for;
- what mode the system is in;
- the outdoor conditions;
- whether a fault is present.
Do not switch it off simply because direct electric heat can be expensive. The useful question is why it is operating and whether that pattern is expected.
Other household loads
If your data is whole-house only, check obvious large loads before diagnosing the heat pump.
An EV charge can make one day look dramatically different even when the heat pump used less electricity than the previous day.
Keep settings changes separate
If you recently changed the room target, schedule, weather compensation, hot-water settings, or holiday mode, include that in the comparison.
Do not make another three changes before you know what the first one did.
When high consumption becomes more concerning
Move beyond simple observation when:
- high use persists across reasonably comparable weather and demand;
- auxiliary heat appears frequently without a clear explanation;
- comfort remains poor despite high electricity use;
- consumption changes suddenly without a corresponding change in weather or household behaviour;
- warning or fault messages appear.
At that point, collect evidence for a focused installer conversation rather than continuing random optimisation.
A useful handoff sounds like this:
The heat pump normally uses roughly this amount in these conditions, but since this date it has used substantially more under similar conditions, with repeated auxiliary-heat indication and no deliberate settings change.
That is much more actionable than “my bill is huge.”
For system settings, read weather compensation for owners. For escalation, use when to call the installer.
Important: There is no universal daily kWh figure that proves a domestic heat pump is efficient or inefficient. Home size, weather, heat loss, emitters, occupancy, hot-water demand, and control strategy all matter.