According to the Energy Saving Trust (2019), heating accounts for around 55% of the average home's energy bills - that's a lot of money so it's important to ensure heating system is working as efficiently as possible, and know when to replace it. Modern boilers are a lot better than ones made as recently as 12 years ago; standards of efficiency has moved on a lot since 2007 when it became law that all installed boilers must be condensing.