What's Your Old Boiler Costing You?
Older boilers waste a chunk of every pound you spend on gas. Answer two quick questions for an honest estimate of what a new A-rated boiler — properly set up — could save you each year.
1. How old is your current boiler?
2. Roughly what do you spend on gas per year?
Estimates use typical efficiency figures for each boiler era against a modern A-rated boiler (92% ErP), assuming around 85% of your gas goes on heating and hot water. The Energy Saving Trust puts the saving at up to £580 a year for the oldest G-rated boilers with full controls fitted. Your real number depends on your home and how the boiler is set up — a free survey gives you the exact picture.
Why "properly set up" matters
A modern boiler is only A-rated in practice when it's commissioned to actually condense — right flow temperatures, right controls, right sizing for your home. Plenty of new boilers are installed in a way that leaves a chunk of that label efficiency on the table. As a Vaillant Accredited Installer, I size and set up every boiler to deliver what it says on the box, and it's why manufacturer warranties up to 10 years come as standard.
If your boiler is from 2018 or later, the honest answer is that efficiency alone rarely justifies replacing it — I'll tell you that to your face. Where it's older, unreliable, or out of warranty, the sums change quickly: the saving, the repair bills you stop paying, and a decade of warranty all stack up together.