What boiler capacity do you need?
Share this free boiler sizing tool with your customer.
Fill in the details on the left and press “Calculate” to see your result.
Calculation method
The result is based on heating water from a 10°C mains inlet to a 60°C usage temperature, applying the simultaneity and storage factors of sanitary engineering standards.
- 01
Fixture demand
Each fixture's unit hot-water draw (e.g. shower 250 L/h, washbasin 7.5 L/h) is multiplied by quantity to find the instantaneous total demand.
- 02
Simultaneity
The instantaneous demand is reduced to a realistic design demand using a simultaneity factor by building type (residential 0.30 · hotel 0.25).
- 03
Storage volume
The design demand is multiplied by the building's storage factor to obtain the required boiler volume in liters.
- 04
Product match
The calculated volume is matched to the nearest catalog capacity of the Omega product suited to your heat source.
About boiler sizing
The most common questions about the calculation logic and choosing the right boiler.
Ask Our Engineering TeamHow is boiler volume calculated?+
It is based on building type, the number of plumbing fixtures and their hot-water consumption. The instantaneous total demand is multiplied by simultaneity and storage factors to find the required boiler volume in liters.
What is the simultaneity factor?+
It is a coefficient reflecting that not all fixtures are used at once. In a hotel, for example, not all showers run simultaneously, so the instantaneous demand is reduced by a simultaneity factor (0.25–0.30).
Should I choose a single- or double-coil boiler?+
A single-coil boiler suits a single heat source (combi/boiler); a double-coil boiler is right if you also use a second source such as solar. The tool recommends the correct model based on your selected heat source.
Is the calculation result exact?+
The result is a quick preliminary sizing. Usage habits, recovery time and site specifics affect the final project, so we recommend confirming the final choice with our engineering team.