What does the energy rating on an appliance actually tell me?
It tells you how efficiently an appliance uses electricity compared with others of the same type and broadly the same size — not how much it will cost you to run. Those are different questions, and the second one is answered by a different number on the same label.
The letter grade is a relative ranking within a product category. An A-rated fridge is efficient for a fridge; it tells you nothing about how it compares with a washing machine. Because the categories are rescaled periodically as technology improves, an appliance rated A a decade ago may rank several letters lower under the current scale, which is why older and newer labels are not comparable.
The number worth reading is the annual energy consumption in kilowatt-hours, printed on the same label. Multiply it by your electricity unit rate and you have an actual running cost. Comparing two machines this way sometimes reverses the impression the letter grade gives — a larger appliance with a better letter can still use more electricity in total than a smaller one with a worse letter, because the rating is normalised for capacity.
The consumption figure is measured under a standard test programme, which may not match how you use the machine. A washing machine's rating is based on a specific eco cycle, usually long and at low temperature. If you habitually run short hot cycles, your real consumption will be higher.
Labels also carry other useful figures that often matter more day to day: water consumption, noise in decibels, and spin-drying efficiency for washing machines.
For appliances that run continuously, such as fridges and freezers, efficiency compounds over a ten to fifteen year life and is worth paying for.