What Size Boiler Do I Need for my House?
Choosing a new boiler with optimal Kw output will make your home cosy and help you save money off your energy bills.
A-rated Worcester Bosch or Vaillant including smart control
What Boiler Do I Need
The Kilowatt output of your new boiler depends on the size of your house and your usage habits. There is no “fit-for-all” recipe when it comes to choosing the right output, however, this simple boiler guide will give you a good idea. Most mainstream domestic boilers come in outputs including 24kW, 27kW, 28kW, 34kW, however a 40kW boiler or even a 42kW boiler is an option for larger houses with bigger demands.
Apartments
Most flats, apartments and small terraced houses with just one bathroom and the number of radiators ranging from one to 8 will find that choosing a 24kW boiler is usually good enough, however it will depend on circumstances.
Semi-detached Houses
What boiler do you need for a 2 bed house? If the number of radiators isn’t higher than 14 and you have no more than two bathrooms, you will be expected to make a choice between a 28kW and a 32kW boiler.
Detached Houses
Larger detached houses with 3 or more bedrooms having two bathrooms and less than 18 radiators will have to look at some of the bigger-output gas boilers. We’re probably looking at up to 42kW output for larger properties.
Can a Boiler be Too Big for My House?
Essentially yes. Decision on what size boiler to install should be based on two main considerations – heating demand and mains water flow rate. Since there is so much confusion surrounding the latter, we think it’s important to look at flow rate into more detail. Boiler manufacturers often use hot water flow rate as a marketing message to convince the consumer to choose their boiler based on a better flow rate. If a company advertises a new boiler that can supply a 14 litres per minute, don’t automatically jump to the offer before considering if your mains supply can support this.
You will need a qualified plumber or heating engineer to measure this, but it is relatively easy to find your cold water static pressure and dynamic pressure, as well as its incoming flow rate.
If your incoming flow rate is just 9 litres per minute, buying a new boiler with 14lpm flow rate will still yield a meagre 9lpm hot water. And this is not because the boiler manufacturer had lied – it’s purely because your mains supply cannot provide more.
If you’re happy with your current flow rate, you don’t need to do anything. You can simply save money on boiler installation by choosing a model that is rated at 9lpm. However, if you think this is not enough, you will either need to upgrade your incoming water supply or buy additional equipment to slightly boost your existing supply.
Installing an accumulator vessel may provide a slight improvement. A typical 60-litre accumulation vessel will cost slightly over £120 plus installation costs and it may boost your water pressure to 3 -4bar enabling you to choose a bigger size boiler for your house.
On the other hand, if your incoming water supply is weak, this step may not provide enough of a boost to justify the extra spend.
Depending on where you live, you can apply with your water supplier to get the incoming pipe upgraded. Typical older style houses will have a 1/2″ pipe feeding the water system and this is what is limiting your flow rate to approximately 9lpm or even lower if the pipework is old. Even a modern combi boiler will struggle with that supply. If you’re dreaming about installing a hot tub, a garden fountain or even a small swimming pool in your garden, there’s no way this old pipework is going to be able to supply it.
In this case an official pipework upgrade is the only option. It is not as expensive as it may sound. Your water supplier may upgrade you for as little as £1,000 depending on your property’s distance from the mainline. That’s good news. What may not be as much of good news is that not every property will qualify for an upgrade. Improving the water feed will not help you if your area is not geared up to support an increased pressure. Two most widespread reason why your application may be turned down is
- Your area has a mains pressure management scheme
- Your property is too elevated and there’s not enough power to deliver more water so high above the sea level
Either way, if you’re looking at the more expensive end of the boiler market, your first port of call should be your water supplier to help you determine viability of the water system upgrade.
How Much Heat Does my House Need?
With the topic of water pressure clarified, let’s proceed to looking at your heating demand. Although the British weather is a rather constant occurrence, a recent study suggests that the spread in residential energy consumption is massive – between 5,000 kWh and 25,000kWh. With such loose guidelines, how do you know what size boiler to choose?
We’d like to provide a generalised estimation based on average figures, however, please note that the actual heat required will depend on multiple factors such as
- Insulation of the house
- Solar position (North – South)
- Building materials used
- Ceiling height
- Personal circumstances etc
What Our Customers Say…
“I was very pleased with the response I had from the Glow Green Ltd company. They sent an engineer to give me an estimate for the boiler installation the very next day and the job was done very neatly within 5 days.”
Mrs Barbara Selwood
“Top company. Did exactly what it said on the contract to the letter. Initial engineer injured in an unassociated mishap. The company replaced him and recovered the job very efficiently. The measure of a good firm surely!”
Mr Wade, Hungerford
“Two very polite young fitters were sent. They encountered several difficulties in our old house, including plaster that dissolved into sand as they tried to fit pipes and a gas meter in a cupboard that required a contortionist to access it, but they maintained a professional, cheerful approach and completed the work as neatly as possible. One fitter had to work an extra day but no extra charge was made.”
Max & Felicity Greene
Is Your Boiler Costing You Money?
Getting the right size boiler is crucial for various reasons. Installing something that is too powerful is going to cost you extra money without providing extra comfort. Although we collect initial data about your house and hot water usage during the online quote, when it comes to booking a free surveyor visit, you will get a more accurate appraisal of the situation and he will confidently answer the age-old question of what boiler do i need for my size house?
How is it different from the pushy salesmen visits carried out by some of the larger installers? We won’t try to upsell you to services and products that you don’t need. Once you’re given a price by the surveyor, that’s the boiler installation price you’re going to pay. There are no hidden charges and we stick to our price promise guarantee. Also, we are so confident in our services that we are happy to beat any like-for-like quote.
The key to choosing the right boiler is figuring out your specific circumstances. The number of radiators in your property will play a major role in making the choice. We have to make sure the boiler installed can cope with the capacity of your radiators. Also an important factor is the hot water usage habits of your family, especially how many showers or taps you intend to run at the same time.#
Although most families will find that a combi boiler fits their lifestyle, there are cases that due to a high hot water demand we would have to advise a system boiler as a better alternative. Busy families that need to use two showers at the same time (think busy mornings and school runs) will find that a combi boiler can’t offer enough output to keep everyone happy.
Installing a new boiler shouldn’t break the bank either. Our finance packages start from as little as £9.99 per month, which means you could actually be saving money each month making your energy-efficient boiler pay for itself in form of lower heating bills.
Our 3 Simple Steps
GET A QUOTE IN 30 SECONDS
Fill in a few details and get your combi boiler price estimate in seconds.
FREE SURVEYOR VISIT ORGANISED
No salesmen involved, no hidden charges! A friendly surveyor visits your property to give you a fixed-price promise.
WE REPLACE YOUR BOILER
Get your boiler installed by an award-winning company. All our engineers are fully qualified and carefully vetted.
WHY CUSTOMERS LOVE GLOW GREEN?
12-Year Warranty
Our boilers come with the option of a 12 year peace of mind warranty
Spread the Cost
With our flexible payment plans, including our popular 0% APR finance
15% Discount
Save an extra 15% of your quote if you accept within 5 days
Accredited
Glow Green are proud to be Worcester Bosch & Vaillant accredited
Quality Control
100% of our installations are digitally audited to ensure full compliance
Award Winning
We are an award-winning business. This year’s finalist for H&V national heating installer 2019
Gas Safe
Our engineers are all carefully vetted and experienced Gas-Safe approved
48 Hour Install
If you’re without heating, we can install your combi boiler within 48 hours
Prices from £1,795 OR £9.99 per month
Everything Included
3 Stress-free Payment Options
Cash Purchase
Interest-free Credit
Boiler Finance
Our Awards
Glow Green is an award-winning expert recognised by a number of industry bodies and associations.
“Glow Green are a modern, forward-thinking company with strong values and high levels of service and customer satisfaction”
Mark Martin, Regional Sales Director, Worcester Bosch Group
Glow Green Limited is authorized and regulated in the UK by the Financial Conduct Authority RN: 692433 for credit broking activities. Finance options are provided by a panel of lenders. Finance available subject to status. Terms and conditions apply. Glow Green Limited acts as a credit broker and is not a lender. Any credit is subject to status, affordability and a credit check. Registered in England & Wales. Company Reg No: 07530174 and VAT No: 135032748. Glow Green Limited, Avalon, 5th Floor, 26-32 Oxford road, Bournemouth, BH8 8EZ.
*(9.9% APR Offer) Representative Example: Cash Price £2,100. Deposit Payable £1,327. Total Amount of Credit £773. Total Interest £425.80. Total Amount Repayable £2,525.80 Repayable by 120 monthly instalments of £9.99. Representative 9.9% APR (fixed). Rate of Interest 9.9% a year (fixed). Duration of Agreement 120 months. Credit is subject to status, affordability assessment and credit checks.
(0% APR Offer) Representative Example: Cash Price £2,100. Deposit Payable £0. Total Amount of Credit £2,100. Total Interest £0. Total Amount Repayable £2,100 Repayable by 24 monthly instalments of £87.50 Representative 0.00% APR (fixed). Rate of Interest 0.00% a year (fixed). Duration of Agreement 24 months. Credit is subject to status, affordability assessment and credit checks.
** The 12 year warranty is only available for customers who have a Worcester Bosch or Vaillant boiler supplied and fitted by Glow Green Ltd and is subject to a Glow Care 100 service contract for the 12 year period.
††Estimated figures based on installing a new A-rated condensing boiler with a programmer, room thermostat and thermostatic radiator controls (TRVs) in a gas-heated detached home from an older boiler without controls. Savings will vary depending on the size and thermal performance of your home. Correct as at May 2015. Source: Energy Saving Trust.