A household energy comparison is a straightforward calculation, but it depends entirely on the figures fed into it. Getting those right is most of the work.
Three inputs decide everything
Every comparison needs the same three things: how much energy you use, what the tariff charges for it, and how long you are committing for.
- Your annual consumption in kilowatt hours, for electricity and for gas separately.
- The unit rate and standing charge for each fuel under each tariff.
- The contract length, and whether a fixed term applies.
Without actual consumption figures, a comparison has to assume a usage level. If that assumption is wrong, the ranking of the options can change, particularly between tariffs that trade a low unit rate against a high standing charge.
Where to find your consumption figure
Your bill or annual statement shows annual consumption in kilowatt hours. If you cannot find it, twelve months of statements or readings lets the figure be calculated, and your online account usually shows it directly.
Consumption moves over time. A change of occupancy, new appliances, working from home or a boiler replacement can shift the picture significantly. A comparison built on a figure from three years ago may not reflect the household you are running now.
Why the cheapest unit rate isn't automatically the best tariff
Electricity and gas are charged in two parts: a unit rate for what you use and a standing charge for the supply itself.
A low-user household pays relatively more of its bill through the standing charge, because it uses fewer units. A high-user household pays relatively more through the unit rate. This is why a tariff that looks attractive on the unit rate can cost more for a household with modest consumption, and why the same tariff can be the right answer for a larger, busier home.
Fixed, variable and time-of-use tariffs
A fixed tariff sets the unit rate and standing charge for the length of the term, which gives certainty but sometimes carries an exit fee if you leave early. A variable tariff follows the supplier's standard rates, which can move up or down.
Time-of-use tariffs charge different rates at different times of day, which suits households able to run appliances or charge a vehicle overnight and suits them far less where most consumption happens in the evening peak.
The end of a fixed term
When a fixed term ends, nothing happens automatically. The account usually continues on the supplier's standard variable rate, which may be higher than the rate you were paying. There is normally no exit fee at that point, which makes it the natural moment to review what is available.
If you are considering a change, check the end date, confirm the meter type on the account and take a reading on the day of the switch so the final bill is accurate. A comparison is only useful if it leads to a decision you are comfortable with, and staying on your current tariff is a perfectly reasonable outcome.
This guide is general information for UK households and businesses. It is not advice on your specific contract, and it does not replace the terms agreed with your supplier or the guidance published by regulators and network operators.