The heating world seemingly struggles to make its mind up about the way it expresses power output, which is made no less easy considering the uncomfortable middle ground the UK adopts concerning measurements. Watts or BTUs – which should you be using? Is one better than the other? It can be a real inconvenience if you’ve used one measurement or the other all your life, only to be confronted by a sea of values you don’t understand when you go shopping for a new heater. In truth, both power measurements are fine but confusion about them is rife nevertheless. Don’t worry though, Heatingpoint is on hand to provide a little more information about what to expect when you’re choosing the size of an electric radiator.
Measurements of Power
BTUs and watts are both units of measurement used in relation to the heat output of appliances, but what’s the difference between them and what do you need to know when you’re sizing up an electric radiator for your home or business?
BTUs (British Thermal Units)
If you’re more familiar with metric, you may not have heard of BTUs or be less confident in using them. BTU stands for British Thermal Unit and equates to the amount of energy needed to raise one pound of liquid water by 1 degree Fahrenheit, at a pressure of one atmosphere. Though it’s called a British Thermal Unit, use of this measurement is mixed within the UK and is far more commonly adopted in America where it’s used to express the power of heaters both gas and electric. However, BTUs are occasionally used in the UK, usually for measuring the heat output of central heating systems. Calculations for room volumes to determine the BTU requirement are typically done in feet, so tends to suit anyone who feels more comfortable using imperial measurements. The metric counterpart to BTUs is the calorie, which is the amount of energy needed to raise one gram of water by one degree Celsius at a pressure of one atmosphere.
Watts are a unit of power representing an energy transfer of one joule per second and is part of the International System of Units. As watts are a set global standard, their use within the UK predominates, although it tends to be more closely associated with electrical products for obvious reasons. When you’re shopping for electric radiators, their power output will often be given in watts, especially if they are a product that is shipped to other countries where this is the preferred measurement. Watts can sometimes be easier to understand when choosing an electric radiator size, as you can easily use their specified wattage to calculate their running cost using the pence per kWh provided by your energy supplier. The electric radiators we offer at Heatingpoint have their heat output displayed in watts.
Watt’s the difference?
It’s a little misleading to say that BTUs can be converted directly into watts as this isn’t strictly true. BTUs are a unit of energy, whereas watts measure the rate that energy is transferred so they don’t directly equate to the same thing. When people talk about converting BTUs into watts, they’re really talking about the conversion of BTUs per hour into watts, which is sometimes written as BTU/h. If you have the wattage or BTU/h figure required to heat your room, it only takes a simple calculation to convert them into your preferred measurement.
Which measurement should I use to choose the size of my electric radiator?
You can use either measurement to work out whether an electric radiator will have enough power to heat your room.
Converting BTU/h to watts
If you know what BTU/h figure you need to heat your living room but need to convert this into watts to make sure you’re purchasing an electric radiator that’s suitable for that space, all you need to do is to multiply your figure by 0.293.
So, for example, if your room needs a radiator with a power output of 3425 BTU/h, you can change this into watts as follows:
3425 x 0.293 = 1003.53
This means you’ll be looking for an electric radiator with a wattage of around 1000, though it’s advisable to round this up to the next available size to ensure the room will be well heated.
Converting watts to BTU/h
Some heating shops will prefer to list their products in terms of BTU/h so to convert watts into BTUs, you can use a similarly straightforward multiplication.
If you know you need a 1800W electric radiator for your room, all you need to do to get its BTU/h equivalent is to multiply the wattage by 3.412.
1800 x 3.412 = 6141.6
This will give you the amount of BTU/h needed to heat your space, but again it’s always a good idea to round this up slightly to the next size to ensure that you’ve got a radiator that will be powerful enough.
As simple as that?
If you’re shopping for electric radiators, or other heating appliances with a near 100% efficiency rating, the above calculations will give you a very good approximation of how the radiator’s wattage equates to its BTU output. However, you should be aware that this is not an exact science, and you may find yourself getting into difficulties if you try to use these rules of thumb to choose other, less efficient heating solutions.
The confusion lies in the fact that the wattage figure quoted on most electric heating appliances is not strictly a measurement of heat output. It’s actually the rate of energy input, which determines how much electricity the heater will use in an hour. If your radiator is 100% efficient, its heat output will be the same as its energy input – so no problems with our radiators. But as soon as the heat output is significantly less than the energy input, the calculation becomes skewed, and you will need a higher wattage than recommended.
How to choose your radiator size at Heatingpoint
Confused? Don’t worry – heating retailers have been grappling with this one for years, and most of them, including us, have removed much of this ambiguity by providing bespoke heating calculators for each type of heating solution. If in doubt, always defer to the sizing calculator or tables advertised with the product – or speak to a sales advisor for a personalised quote tailored to both your home and your chosen heating system. Sometimes this means bypassing BTUs altogether – but most people find this makes things easier and less confusing.
At Heatingpoint, we provide an easy to use electric radiator calculator that will give you a minimum wattage requirement in moments, and by using the calculations above, this can easily be converted into BTUs if preferred.