What size boiler should I install?

When you consider that the boiler is responsible for providing your home with heating and hot water all day, every day, all year round, you might say that it's one of the more important investments that you'll make in your home... add to this the fact that most boilers can last well over a decade, and sometimes even up to 15-20 years, it's imperative that you find the right boiler to meet all of your needs. 

This isn't as easy as it seems however, which is why we've provided some best practices below to help you size your new boiler...

The basics

How is boiler size measured?

Boiler size refers to the output of the boiler in kilowatts (kW). Generally speaking, the more heat and hot water you need, the higher the kilowatts will be. 

Should I oversize my boiler to be safe?

If we're living in the 2000's still, we'd definitely recommend oversizing your boiler so you can compensate for heat loss. Nowadays, with our more energy efficient boilers that have minimal heat loss, no, do not oversize your boiler. Oversizing your boiler can actually result in you wasting energy, meaning you'll inadvertently be increasing the cost of your energy bills. 

Sizing your boiler

Does your current boiler meet your needs?

This is the best place to start. Does your current boiler meet your needs? I.e. would you be happy with swapping your boiler with a straight replacement, or would you like to upgrade/downgrade your boiler?

Ask yourself... Am I running out of hot water regularly? Does my home take too long to heat up (this could be a separate issue altogether)? Is anybody moving out in the near future, do I need such a powerful boiler?

If you find yourself answering yes to any of these questions, you might want to consider resizing your boiler to meet your needs. 

Hot water demand

Most modern homes use a combi boiler system. They provide heat and hot water direct from the mains and they're practical and fairly low cost to run when their is just one bathroom to serve, making them suitable for smaller homes and smaller families. 

If however you have a large family and/or two bathrooms, and you have a combi boiler system, it's definitely worth considering resizing your boiler to a larger system, preferably to a conventional boiler system with hot water tanks so you always have enough hot water.

Number of radiators

Another key factor that will have an effect on the size of boiler you need is the number of radiators that you have in your home. 

An average 3-4 bedroom house will have around 10 radiators, where a 24-30kw combi boiler is suitable in most cases. A larger house with more radiators or and en-suite bathroom will generally need a larger boiler, typically between 30-35kw. If you have an even larger home with 3+ bathrooms and 15-20+ radiators, you'd be best off considering a 35-42 kw combi boiler, or changing over to a conventional system boiler. 

Other factors

There are other factors that you need to consider like heat loss, the type of fuel that you're using, water pressure and a few other minor factors, all of which together can change your choice of boiler. 

Would you like help sizing your new boiler?

If you would like help sizing your new replacement boiler, feel free to get in touch with our gas engineers in Hillingdon. We're more than happy to size your boiler and provide you with a free boiler replacement quote. 

Call us today on  07919 156562 or send us a message via our contact form. We'll look forward to hearing from you soon.