Part of our guide to The Home Maintenance Calendar, Month by Month
A bill that suddenly rises feels like a billing error. Occasionally it is. Usually it is one of a small number of causes, and they are worth checking in order of cost.
The bill itself — period length, estimated reading, rate change. Then the weather against the same month last year. Then equipment, because a system running constantly is both the most expensive cause and the most likely to be missed.
Start with the paperwork, not the boiler
Billing period length. A 35-day period against a 28-day one is 25% more consumption for no change in behaviour.
Estimated versus actual reading. Estimates correct eventually, and the correction can be large. The bill will say which it used.
Rate changes. Tariffs change, fixed terms end, and time-of-use rates shift seasonally. The unit price on this bill against the last one answers it in seconds.
These cost nothing to check and explain a good share of unexpected jumps.
Then the weather
Heating and cooling dominate domestic energy use. A colder-than-usual month or a longer heatwave moves the bill substantially with no change in habits.
Compare against the same month last year rather than last month. Comparing January to December tells you about the season, not the house.
Then the equipment
A system running constantly. A heat pump or air conditioner that never cycles off is either undersized for the conditions or faulty. It is the most expensive failure mode and easy to overlook because it is quiet and continuous.
A failing water heater. Sediment and failing elements make it work far harder for the same hot water.
A stuck auxiliary heater. Backup electric heat that engages when it should not is a well-known cause of sudden large bills.
Something left on. A heater in a garage, a pool pump on an old schedule, a dehumidifier running unattended.
Look at usage when the house is empty or asleep. That baseline should be low. If it is not, something is running that should not be — and finding it matters more than any efficiency tip, because a constant draw runs all day, every day.
Related reading
- What uses the most electricity at home
- Repair or replace an ageing air conditioner
- Heat pump vs central air
This is general information — see our disclaimer.
Frequently asked questions
Why would a bill rise with no change in use?
Common causes are weather, a rate change, a longer billing period, an estimated reading, failing equipment, or something running constantly that should cycle.
What is an estimated reading?
A bill based on a predicted rather than actual meter reading. It corrects later, sometimes as a large catch-up bill.
Which appliance uses most?
Heating and cooling usually dominate, followed by water heating. Small devices rarely explain a large jump.
How do I find a constant draw?
Compare overnight or away-from-home usage against normal. Anything substantial when the house is idle is running when it should not be.
Sources
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