When it comes to efficient home heating, gas combi boilers are one of the UK’s top choices—and it’s easy to see why. These clever systems combine central heating and hot water into a single, compact unit, making them perfect for space-conscious homes. Whether you’re upgrading an old boiler or installing one for the first time, understanding how combi boilers work, what they cost, and which brands perform best can help you make the right decision. In this guide, we break down everything you need to know about gas combi boilers—from how they operate to the top models on the market today.