Boiler guide · 5 min read · Updated October 2026
30kW combi boilers: who they suit and what they cost
The 30kW band is the UK's most popular combi size. Which homes it suits, the models worth shortlisting, and fitted prices.
Who a 30kW combi suits
A 30kW combi is the sweet spot for a typical three-bed semi or terrace with one bathroom and up to around 15 radiators. It delivers roughly 12 litres of hot water a minute — enough for a good shower, not enough for two showers at once.
The 30kW models in our range
From our fitted catalogue: the Worcester Bosch Greenstar 2000 30kW (£2,470 fitted), the Greenstar 4000 30kW (£2,635 fitted) and the Greenstar CDi Compact 30kW (£3,075 fitted) for tight spaces. Our supply-only shop lists dozens more 30kW packs across ten brands — filter by 30kW in the shop to see them all.
When to step up or down
- One bathroom, smaller flat — a 24–25kW combi is usually enough and cheaper
- Two bathrooms used at once — look at 35–40kW, or reconsider a system boiler with a cylinder
- High hot water demand — check the flow rate at a 35°C rise on the product spec, not just the kW
Price check
Fitted, our 30kW combis run £2,470–£3,075 including VAT. Supply-only 30kW packs start lower in the shop. Every price on this site is the real price — no survey-day inflation.
Common questions
Is a 30kW combi big enough for a 3-bed house?
For most three-bed homes with one bathroom, yes. If two showers run at the same time regularly, step up to 35kW+ or consider a system boiler with a cylinder.
What is the best 30kW combi boiler?
In our fitted range the Greenstar 4000 30kW balances price (£2,635 fitted) and a warranty extendable to 10 years with registration and conditions. The shop lets you compare every 30kW pack by warranty length.
Ready for a real price?
Build a fitted boiler quote in about two minutes, or browse over 700 supply-only boiler packs in the shop.