# Radiator Calculation - Calculate the performance of radiators

- The factors
- Calculation of heating power
- Step 1: Relevant sizes
- Step 2: Determine heating capacity
- Step 3: Calculate radiator output

- Selection of the right radiator

Whether a new building or a modernization - only by selecting the right radiator you can heat the rooms optimally. Radiator performance is an important factor in the selection process. It must be calculated and determines the size of the panel radiators for each room. Read how to carry out the radiator calculation and thus ensure ideal heating.

Modern heating systems have at least one heating element in each room, the size of which must be precisely determined. A too small model does not provide the desired performance and is therefore not suitable. A subsequent change would mean that either a second heater body would have to be attached, which would be associated with modifications of the entire inlet and outlet system, or that you need to replace the relevant heating body completely. Therefore, it is important to perform the calculation precisely. It is implemented in a few steps. In general, it is advisable to buy the heater body slightly larger than was charged to ensure the provision of the service in any case.

The required heat output can be determined in only 3 steps.

## The factors

By knowing the radiator performance, you can choose the right radiators for your house. This is important to ensure optimal function. To perform the calculations, you need different information:

- Heating flow temperature
- Heating return temperature
- room temperature

Above all, the difference between older central heating systems and modern heating systems is striking. While newer variants are operated in the low-temperature range, the older systems often operate with flow temperatures of 80 to 90 degrees Celsius. This temperature specification has a direct influence on the room radiators: at a low flow temperature, the radiator must be larger than at a high flow temperature.

## Calculation of heating power

In order to determine the heat output, you have to proceed in three steps: First you determine all the necessary information, then you work with a table and finally a rule of thumb is used.

### Step 1: Relevant sizes

It is important that you know all the necessary information:

**Determine the room size** The radiator output depends on the room size, as this determines the air volume, which must be heated. If it is a rectangular room, first measure the length and width of the room. Now multiply these two values, this gives you the base area.

**Example:** A room is 4 meters long and 3 meters wide. Thus it has an area of 3 meters * 4 meters = 12 square meters.

If it is not a rectangular room, then you have three options:

- Estimate the floor area roughly by comparing the room to other rooms whose floor space you already know.
- Draw the floor plan on a piece of paper. Decompose the surface into known geometric shapes, such as several rectangles, and calculate the area of each shape. Now add all surfaces together.
- It is an approximately rectangular space ">
Relevant factors ### Step 2: Determine heating capacity

Now read off the required heating power from the corresponding table. Here an excerpt for temperatures of 18 to 24 degrees Celsius:

Table 1: Houses with a year of construction until 1982

18 degrees Celsius 111.6 W / m²

20 degrees Celsius 121.6 W / m²

24 degrees Celsius 141.7 W / m²Table 2: Houses with a year of construction between 1983 and 1994

18 degrees Celsius 90.9 W / m²

20 degrees Celsius 99.2 W / m²

24 degrees Celsius 115.9 W / m²Table 3: Houses from 1995 onwards

18 degrees Celsius 73.9 W / m²

20 degrees Celsius 80.8 W / m²

24 degrees Celsius 94.5 W / m²### Step 3: Calculate radiator output

The corresponding formula is:

**Room size * Heating power = radiator output that is needed**An example:

Suppose you live in a house that was built in 1990. The floor space of the living room is 20 square meters. You decide for a room temperature of 24 degrees Celsius. In this case, you first of all present all relevant factors clearly:- Room size: 26 m²
- Temperature: 24 degrees Celsius
- Year of construction of the house 1990

Next, read the heat output per square meter in the relevant table:

In this case, the second table is the right one. Here a value of 115.9 W / m² is given at a temperature of 24 degrees. Now multiply the room size of 26 m² with the area coverage of 115.9 W / m² and you get a required power of

**3, 013 watts.**## Selection of the right radiator

Once you have calculated the radiator output, you can choose the right radiator. In stores or online in the shops tables are provided, so you can find the right models based on various information. In addition to the performance, the flow temperature and structural restrictions are crucial for the size.

**Online Calculator**Some hardware stores offer the use of online calculator for free, so you can calculate the right heating power here as well. In any case, it is important that you follow the manufacturers' tables when selecting the radiators to select the correct models.

**Tips for quick readers:**- Year of construction of the house in experience
- Calculate room size
- Floor area of the room: length * width (rectangular)
- note the desired room temperature
- Read power per square meter in tables
- multiply the area output by the square footage
- the result is the sought service
- Online calculators are often offered for free
- Select radiator model based on the data