What is BTU? A Guide to British Thermal Units

Let's say you're hunting for a brand-new Heated Towel Rail or a Designer Radiator, for argument's sake. You're busy narrowing your search for a specific brand, style and orientation. Once that's been sorted, it's time to look through the description, and you come across "BTUs" with some random numbers next to it. Why?

BTUs are essential when deciding on a new radiator, as they will tell you how much power is needed to heat up the area efficiently. Sounds confusing. Why can't you buy a radiator/ heated towel rail you like the look of and be done with it? With this short and sweet explanation, you can make the best choice for your new heating system.

What does BTU stand for?

BTU stands for British Thermal Unit. This type of measurement is common practice in the UK, but it is also used worldwide for air conditioning systems, cooking devices and pellet stoves.

As BTU is the standard measurement for all Heated Towel Rails/ Radiators in the UK, it would be wise to check on the product specification constantly.

Why is BTU important?

When searching for your dream radiator, the BTU output will determine how much energy will be used to comfortably heat the desired room, whether it's the bedroom, kitchen or bathroom suite.

How is BTU measured?

British Thermal Units are the measurement used when measuring thermal energy. It takes to heat one pound (0.45kg) of water by 1°F (-17°C). To summarise, when you check the BTU Output in any radiator, you learn how much the radiator operates to heat or cool down the room.

What BTU Output do I need?

Workout out the correct BTU output for your room is essential. Try and use these simple tables to find the correct British Thermal Unit:

Room Height (m) Length (m) Width (m) Total Single Glazing Doors/ Windows Total (BTU)
Bathroom x x x x 148.5 =
Bedroom x x x x 132 =
Living Room/ Dining Room x x x x 165 =
Kitchen/ Hallway x x x x 136 =
Room Height (m) Length (m) Width (m) Total Double Glazing Doors/ Windows Total (BTU)
Bathroom x x x x 121.5 =
Bedroom x x x x 108 =
Living Room/ Dining Room x x x x 135 =
Kitchen/ Hallway x x x x 81 =

Another way of figuring out your BTU Output is to use B&Q’s Online BTU Radiator Calculator.

Is Higher or Lower BTU better?

The higher the BTU output, the greater the heat output will be. For example, the Reina Coneva 1800 x 300mm Vertical White Radiator is ideal for larger spaces like a Living Room. On the other hand, the Reina Aliano 500 x 500mm Vertical Designer Towel Radiator has a BTU output of 706, meaning it is ideal for heating towels but only part of the room.

If the BTU output is higher than required, you'll likely be burning your hard-earned cash on unnecessary heating/ energy bills. If the BTU is too low, the temperature will be constantly turned up to the maximum.

Are BTUs measured Per Hour?

In most cases, when you find the BTU Output for your radiator or heated towel radiator, it will generally refer to the BTU per hour (BTU/hr) that is used to heat your room.

Can you convert BTUs to Watts?

British Thermal Units can be converted to a Watt Output. 1W is equivalent to 3.41 BTU/hr. To convert BTU to W, you need to divide by 3.41. However, to convert W to BTU, you must multiply by 3.41. For example:

1 BTU/hr = 0.293071 W

10 BTU/hr = 2.930710 W

100 BTU/hr = 29.307107 W

1000 BTU/hr = 293.071070 W

What affects the BTU Output?

Generally speaking, there are two main factors that can affect the BTU output in any room design. These are:

Heating Temperature – the higher your desired temperature, the more power the radiator will have. Depending on which room the radiator is installed in, you can determine which new style you can purchase for your hallway, kitchen etc. After all, why spend extra money on a more powerful radiator when it isn't necessary?

Heat Loss – all homes and rooms are different. There will always be somewhere for heat to escape from, regardless of how well your walls are insulated. These factors include the overall size of the room (small or large), single or double-glazed windows, the amount of insulation, wall type (e.g., outside wall) and external doors.

Why should I buy a Radiator or a Heated Towel Rail from ShowerstoYou?

For the past 38 years, ShowerstoYou has provided various Radiator and Heated Towel Rail designs for all modern and traditional homes. From Stainless Steel Radiators to Electric Towel Rails, we have experts who live and breathe all aspects of heating and provide our customers with an array of knowledge.

Our Radiators and Heated Towel Rails include comprehensive manufacturer warranties for total peace of mind when ordering.

Browse our ranges today.