What boiler do I need...

What boiler do I need?

What boiler you need depends on your home and your needs. Here’s a quick guide to help:

🏠 1. Combi Boiler (Combination Boiler)

✅ Best for small to medium homes with 1-2 bathrooms
✅ No separate water tank needed
✅ Heats water on demand — good for hot taps and showers
✅ Space-saving and energy-efficient

Frequent Questions

Will a combi boiler fill a bath?

Most modern combi boilers (around 24–30 kW or higher) can provide enough hot water to fill a standard bath (typically 150–200 litres). Higher output models (30–40 kW) can fill larger baths or do it more quickly.

Because combi boilers heat water directly from the mains, you water pressure plays a big role. If your mains pressure is good it should fill a bath in 10-15 minutes. Poor mains pressure = slower fill.

If you're running taps, a shower or appliances at the same time this can reduce the flow to the bath.

Single task limitation. Most combi boilers are hot water priority. So if you use a lot of hot water i.e. shower after shower etc whilst it is producing hot water it is not producing heating. During winter months this can be noticeable as the radiators cool down.

Lifespan of a combi boiler. Typical lifespan is 10 - 15 years with annual servicing. Poor maintenance or hard water areas can shorten life. Good brand and quality installation matters a lot.

Is it cheaper to run a combi boiler than normal boilers? Generally, yes for smaller to medium homes as no hot water storage, lower installation costs, fewer parts. But not suitable for high hot water demands.

Optimal running temperatures. See below for heating and hot water temperatures.

🔥 For heating (radiators):

• Most economical: ≈ 55–60°C

• Lower flow temperatures (around 55°C) allow modern condensing boilers to run in their most efficient mode ("condensing" more heat from the flue gases).

• Too low (below 50°C) may cause the house to feel cool or prevent proper radiator heat-up.

🚿 For hot water (taps & showers):

• Recommended: ≈ 50–55°C

• Hot enough to avoid risk of bacteria (like Legionella), but not so hot that you waste energy or risk scalding.

• Many combi boilers heat water instantly, so adjust based on comfort.

🏠 2. System Boiler

✅ Best for medium to large homes with more than 1 bathroom
✅ Uses a hot water cylinder (tank)
✅ Great if you want strong water pressure for multiple taps/showers running at once. Ideal if low mains pressure in property.

Frequent Questions

Do I need a cold water tank — takes water directly from the mains so no tanks are required.

Limited hot water supply — once cylinder is empty, needs time to reheat.

Higher maintenance costs - two appliances to be serviced (boiler and cylinder).

🏠 3. Regular / Conventional Boiler

✅ Best for larger homes with old radiator systems or where you already have a hot water tank
✅ Works with a separate hot water cylinder and cold water tank
✅ Ideal if you need lots of hot water or already have a traditional system

Questions as above. You can have the cold water tank removed if already fitted and cylinder installed that works directly of the cold main supply.

Limited hot water supply — once cylinder is empty, needs time to reheat. But backup immersion heater is ideal to heat water during summer months when heating is off.

Higher maintenance costs - two appliances to be serviced (boiler and cylinder).

Less energy efficient than combi or system boilers in smaller homes.

Choosing the right boiler depends on:

• The size of your home

• Number of bathrooms

• How much hot water you use

• Your current system (new install or replacement)

• Your budget

Choosing the right boiler for you raises a multitude of questions from what is most suitable for my property, the most energy efficient, how long is the warranty, how long will it last and how much will it cost...

The most relevant questions answered below

With all this information at hand it can still be a dilemma choosing the right boiler. We are happy to help

Book your FREE site visit where an engineer can discuss your options