What is a BTU?

BTU (British Thermal Unit) is a unit of measurement for energy, adopted in the United States and United Kingdom, and is often used alongside or instead of Watts (W). A BTU is defined by the quantity of heat required to raise the temperature of one pound (approximately 454 grams) of water from 60 to 61 degrees Fahrenheit. BTUs/h are normally used to define the cooling power of air conditioning systems as well as the heating power of fuel.

Why do I need to know this?

Before selecting your radiator, you need to know what the heat output requirements of the room are. The calculator accurately works out the heat energy required for your room per hour, ensuring each room stays at a comfortable temperature without wasting energy or money.

How can I get a more accurate estimate?

Adjustments can be made to the estimate based on insulation, windows, sunlight, and climate.

Insulation: Higher insulation (R-value) means less heat loss.

Windows: More windows and larger windows mean more heat loss.

Sunlight: Rooms with more direct sunlight means less heat is needed.

Climate: Colder climates require more BTUs to heat.

Ceiling Height: Most estimates are calculated for a standard 8-foot ceiling.

Example Adjustments (for heating):

For a room facing north, add 15%.
For double-glazed windows, subtract 10%.