What 14 litres a minute means for your shower

When people compare combi boilers they tend to look at the kW figure. What you actually notice every morning is something else: how much hot water comes out of the shower. That is the flow rate.

kW and flow are linked

A combi’s output in kW is mostly about how quickly it can heat water. A bigger output heats more water per minute, so the flow rate goes up with it. That is why the larger models of each boiler give the best hot water.

How flow is measured

Flow is given in litres per minute at a 35 degree rise. That means the boiler can take cold mains water and warm it by 35 degrees at that rate, which is about right for a comfortable shower in most of the year. In a very cold spell the incoming water is colder, so you get a little less.

The four boilers we fit

• Worcester 8000 (32, 35 or 40 kW): up to 16.3 L/min, the most of the four.
• Baxi 800 (24, 30 or 36 kW): up to 14.7 L/min.
• Ideal Logic Max (24, 30 or 35 kW): up to 14.3 L/min.
• Vaillant ecoFIT pure (25, 30 or 35 kW): up to 14.1 L/min.

All four are A-rated, and all come with up to 10 years of manufacturer warranty.

What the numbers mean at home

For a flat or a house with one bathroom, any of the four will run a good shower. Where the difference shows is when two outlets run together, say a shower upstairs and the kitchen tap. A higher flow figure means each one holds up better.

Your mains matter too

A combi can only deliver what your incoming water supply allows. If your mains pressure or flow is low, a bigger boiler will not fix it. If we spot that from your photos or on the day, we will tell you.

Picking yours

For most homes, the Baxi 800 is the one we fit most. For two showers at once, the Worcester 8000. If you are unsure, tell us how many bathrooms and people you have, and we will recommend one with your fixed price, from £1,900 fully fitted with VAT.

Bigger home? Read combi or cylinder, or get your price.