What is BTU? How to choose the right heat output for your home
If you’ve ever found yourself browsing for a new home heating appliance and wondered ‘What is BTU?’, you’re not the only one. The world of fireplaces can be filled with confusing terminology, especially when you’re not sure what’s jargon and what’s important.
British Thermal Units (BTUs) are just a measurement of heat.
BTUs indicate the heat content of energy or fuel sources, such as radiators, air conditioning units, and fireplaces. (To be more specific, BTUs measure the energy needed to heat one pound of water by one degree Fahrenheit.)
So, how does this correlate to fireplaces? The BTU rating of a fireplace directly relates to an appliance’s heating capacity. Essentially, a higher BTU rating signifies a greater heat output.
For example, 2kW electric fires consume 2,000 watts of electricity and can generate up to 6,800 BTUs (British Thermal Units) every hour. Gas fires with higher heat outputs (typically between 2kW and 8kW) can produce anywhere between 20,000 and 60,000 BTUs!
Fireplace shoppers with greater awareness of BTUs may be able to make a more informed final decision.
Why use British thermal units?
BTUs can provide great insight into how well an appliance will warm your home before you purchase it. It’s not all about choosing the fire with the highest BTU! While yes, a higher BTU indicates a higher heat output, this may not always be what your home needs.
Why consider BTU?
All too often, shoppers find a fireplace that matches their exact aesthetic preferences (e.g., hole-in-the-wall electric fire, freestanding gas stove) and think: that’s the one!
But before purchasing, they need to consider the size of their room and the unit’s heat output (and BTUs). Failure to consider these factors may result in a fire that’s either too powerful or too weak.
How to calculate BTU
So, how can homeowners calculate the right BTU for their homes?
To work this out, measure the length, width and height of the space where you plan to put the fire. Then multiply the figures together. Here’s an example for a room that measures 4m in width, 8m in length and 2m in height:
Volume m³ = 4m x 8m x 2m = 64 cubic metres
There you have it: your room has 64 cubic metres of space. Next, homeowners should estimate how well their home is insulated. Exact figures aren’t necessary for this (you won’t need to contact a professional or even see your insulation in person).
You just need to evaluate what you do and don’t have.
For example, most new builds in the UK are constructed to meet energy efficiency requirements: this means they’ll have insulated cavity walls (by law), roof insulation (270mm) thick, and, more often than not, double-glazed windows.
For labelling purposes, this is a good level of insulation. If your home has some insulated cavity walls and a few windows with double glazing, we can call this average insulation.
Properties that are fairly old or that you are aware haven’t had their insulation checked by a professional in the last 15–20 years are poorly insulated. Depending on where your home lies on this scale, you can divide its volume in cubic metres by one of the following figures:
Insulation levels |
Good | Volume in cubic metres ÷ 25 = recommended kW output |
Average | Volume in cubic metres ÷ 15 = recommended kW output |
Poor | Volume in cubic metres ÷ 10 = recommended kW output |
If we use our previous example of a room with a volume of 64m³, we can calculate the recommended kW of a fireplace three different ways (depending on the quality of the home’s insulation):
64m³ ÷ 25 = 2,500 kW
64m³ ÷ 15 = 4,200 kW
64m³ ÷ 10 = 6,400 kW
What affects BTU output?
The two main factors that affect BTU are the size of your room and the home’s insulation quality. However, your final decision may also be influenced by other things, such as additional heat sources in the room (e.g., a radiator) and the preferred level of warmth.
Fireplaces usually display heat output as a range or a band, like 2–4 kW or 5–7 kW. The higher of those two figures (4 and 7) indicates the appliance's maximum heat output.
If you know you don’t want your room too warm, choose a fireplace that’s still within the recommended range for your space but not the maximum (e.g., a maximum heat output of 3kW or 6kW).
After all, there’s no point paying for heat you won’t use!
Shop for electric and gas fires with Fires2U!
So, what is BTU? It’s crucial to those shopping for a new fireplace. Armed with this knowledge, you can now go out and browse electric fireplaces and gas fires from top-name brands like Celsi, DRU and Crystal Fires.
