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Our Comprehensive Guide to BTUs

This week we're getting technical on the Tap Warehouse blog, in order to guide you through everything you need to know about BTUs.

We will start by explaining what this unit of measurement is, then discuss why exactly it is so important to be in the know, before moving swiftly onto introducing our incredibly useful BTU calculator.

This tool is used by many of our customers as it can instantly tell you just how much heat output your rooms require and is really the only help you need when choosing the power of your perfect new radiator from our expansive online store.

We understand that it can seem like like a lot to take in but we can promise you that you will be a BTU expert by the time you have read this post and a master in one of the many mysteries of the world of home heating!  

So, if you began this article by thinking,  “I don’t even know what a BTU is!” then you need not worry about that much longer. Sit back, relax, get your thinking cap on and get ready to become a BTU mastermind.

What does BTU mean?

If you have been looking through our vast selection of radiators and heated towel rails then you will have been sure to have seen these three letters. And if you have not braved a Google search yet, you will be asking yourself “what is a BTU rating?”

Well, wonder no more!

BTU is the abbreviation of British Thermal Unit and is defined as "the amount of heat required to raise the temperature of one pound of water (0.45 litres) by one-degree Fahrenheit".

In short, it’s a quick and easy way of confirming exactly how much energy you need your radiator to put out to ensure that the room in which it’s destined to go is kept nice and toasty. And so as you can imagine, it is an invaluable bit of knowledge – after all, no-one wants to be  unable to heat their lounge sufficiently once the cold of winter sets in.

BTU isn’t only used in the UK, although it is most common here and in the home heating industry. The measurement, which is generally associated with energy and power, is also used throughout the rest of the world to rate the output of air conditioning units and steam generators.

So, now that we are all clear on what BTU means, let’s move right onto why BTU is so important to you in your home heating shopping journey.

Why does the BTU affect me?

Getting the BTU measurements right for each room in your home is vital to making sure you are keeping warm, not wasting energy and most importantly of all, not spending too much money on heating.

Picture this: winter has rolled in, you are sat in your home and it is a tad chilly. And so you think, “must be time to turn on the radiators!”

But you did not check the BTU requirements for your rooms before you purchased your radiators, and so you are faced with at least one though more likely all of the following problems…

Too Little BTU Output

Too little BTU output from your radiators and you won’t be able to heat your room up to the required temperature, leaving your room cold and uninviting.

If you do find that you have installed radiators without a high enough BTU output rating, then the heating will need to be pumped up to maximum the whole time, which is of course incredibly inefficient!

Your room will never reach optimal temperature, so be sure not to make this mistake! And even with the radiators on maximum, the temperature outside may dictate that you still need a coat to stay warm!

Remember though, it is always possible to combine BTU outputs to reach your requirement, so as a solution you could install another radiator into your room. But it is far from optimal, we are sure you will agree.

Too Much BTU Output

Too much BTU output from your radiators and they will be producing too much heat. You will have to keep the radiator on lower settings at all times, and may well open yourself up to surprisingly high energy bills – something that the team at Tap Warehouse would not wish on anybody, especially with Christmas approaching.

The good thing about radiators is you can always turn them down, so it is better to have too much BTU output then too little, but we recommend that you get it just right! What’s the point in splashing out on a powerful new radiator if you cannot let it do its thing properly?

Getting the BTU readings right for your home is therefore incredibly important for optimal temperature control and your ability to create warm, inviting rooms.

To think about it another way – you wouldn’t put a small, single panel radiator in a huge open plan kitchen dining room (unless you live on the equator) just as you wouldn’t put a huge five column radiator in a small cloakroom bathroom in your house (unless you live in Antarctica).

How do I Calculate my BTU?

You can use our super handy BTU calculator to calculate your required BTU. Simply enter your room dimensions and information, and find out the BTU you'd need to heat your room!

Using the Tap Warehouse BTU Calculator

Once it's ready, follow these steps using our BTU calculator to work out your own BTU.

First, have your tape measure (or laser measurer) ready so that you can note down the height, length and width of your room.

Enter this information (in imperial or metric – whatever you prefer) into the calculator and it will work out the volume of your room.

Then we just need a couple more bits of quick information such as how many windows you have in the room and whether they are single pane or double glazed.

You will also need to let us know what type of room you are heating along with what is above and below the room.

Finally, we need to know the type of outside wall, so add this in as the final piece of the puzzle.

From there, our BTU calculator will work its magic and give you an accurate estimate of the BTU requirement needed to heat your room! Now just be sure to write this figure down and refer to it when choosing your radiator for complete peace of mind.

Finding that Perfect Rad


If you have found your room has a high BTU requirement, you will need a more powerful radiator or even combination of two radiators. Remember, the total amount of combined BTU output can meet your heating needs.

Generally, column radiators are known for producing the highest BTU output per area so if you’ve got a high BTU requirement we highly recommend this radiator style.

For rooms with a low BTU requirement, you can get away with less radiators – sometimes even just one small radiator can meet your BTU output needs.

Radiators at Tap Warehouse

Now that you know what your BTU requirement is, having used our handy Tap Warehouse BTU calculator, you can now browse our extensive range of radiators and find exactly which radiator suits your needs best.

Of course, we have tons of different styles of designer radiator available including column radiators, vertical radiators and towel radiators. Selecting the correct style is very important when choosing your radiator, but not as important as the BTU output.

Our radiators come in a range of different brands, prices, finishes and shapes so you will be sure to find something that floats your boat. And you can filter results by your desired BTU to find exactly what you need with ease. Be sure to check out our selection of different brands available as well as browse our promotions.

If you find something you like then be sure to make your mind up fast – our sale stocks are highly limited and often sell out in the blink of an eye. Yet while they sell fast, they will certainly last, with a guarantee of between 5 and 20 years to be found on every product. We also offer next day delivery for when you need your radiator fast as the dreaded winter months set in.

Still Need a Hand?

So now you know what exactly is meant by BTU, how to work out the radiator size needed for a room, and how to calculate BTU yourself or using our handy BTU Calculator!

However, if you're still a little unsure or simply want reassurance, please give contact our friendly support team right here! We are always on hand to help, whether it is to guide you through the world of BTU or anything else to do with your bathroom design projects.

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