# How to Calculate Boiler Capacity

• 1-2 hours
• Beginner
• 10-50
What You'll Need
Calculator
Pen
Paper
Tape measure

The modern design of a boiler means that there are a wide variety on the market, many of which have a range of capacities. Getting the right boiler can be a complicated business, so before you go ahead and buy a plush boiler, check that you are purchasing the right system by working out how much water your boiler will actually use. You may be surprised by how little water you can fit into some of these devices, so don't just just by appearances.

While hot water boilers are one of the easiest ways of heating your home, and getting hot water, there are still complex procedures involved in calculating boiler capacity. Getting this job done doesn’t need the assistance of a professional if you have some basic home improvement skills. All you have to do is follow a few simple guidelines to get the job done quickly and easily.

## Step 1 – Measuring the Need

Measure the recommended heat output of your radiators. Your manufacturer may have made a note of this required capacity on the radiator itself, but if not, then you will have to work it out yourself by measuring the radiator. You will also need a conversion table, many of which are available online.

## Step 2 – Adding Extras

Add the extras to this calculation to work out exactly how much hot water your boiler needs to produce to keep your radiators ticking over. You will have to add 35kw to each radiator in order to account for pressure switches and valves. You should then also add 10% to the total calculation to allow for very bad weather, snow showers for example, which can happen even in warm regions.

## Step 3 – Doing the Calculations

Once that is completed, you will have to add the totals together to produce the required amount. Take the height and width of your radiator, and use the table to calculate how much power this radiator produces. For example a single fin radiator with a height of 2 feet can produce 600 w of energy. You will have to use the tables to calculate exactly what your device will need, as double radiators, those with fins, or other features may all affect the calculations.

## Step 4 – Finishing

Before you finish the project you will have to take this calculation to your show room and check the amount you need with the capacity of the boiler. You may find, for example, that a small boiler will produce enough heat over a day to power all of your radiators, while a larger one may produce less power, depending upon the thermostat and the control of water production. The best boiler capacity for your needs is one which can heat all of your radiators at once.