Energy providers default customers to expensive 'standard variable' tariffs at end of fixed terms. Switching annually (or fixing for 1-2 years on better deals) saves £100-400 per year for most households.
How to check
Use comparison sites (MoneySavingExpert Cheap Energy Club, Uswitch, GoCompare). Compare current tariff against alternatives. Most providers offer better rates to retain customers when called — try this before switching.
What to look for
Fixed rates lock in price for 1-2 years (protects against base rate rises). Variable rates may be cheaper now but change. Smart meter tariffs often slightly cheaper. Green tariffs sometimes premium.
Annual habit. Set diary reminder for renewal date. Most UK households leave £200-400/year on table through inertia.