ᐅ How does a high supply temperature in underfloor heating affect heating costs?

Hello.
First of all, thank you very much for your help.

I have a question regarding underfloor heating with a pellet boiler.
(Multi-family building)

- Does a high underfloor heating flow temperature (e.g., 50 degrees Celsius (122°F) in a 1970s KfW multi-family building) affect the reading on the individual apartment heat meters (kWh value), or only the consumption of the pellets needed?

In other words, would the heat meter reading for an individual apartment be the same at a lower flow temperature, assuming usage stays the same (i.e., room thermostat setting and weather conditions unchanged), as it would be if the flow temperature, for example, were 5 degrees Celsius (9°F) higher?

The heat meter only measures the flow volume when the underfloor heating is active, correct? Whether 50 degrees Celsius (122°F) or 45 degrees Celsius (113°F) is flowing through, the 45 degrees Celsius (113°F) should warm the room to the desired temperature just as well as 50 degrees Celsius (122°F). The flow rate in terms of volume should be the same, right?

It makes sense to me that the pellet boiler needs more energy (pellets) to supply 50 degrees Celsius (122°F) than 45 degrees Celsius (113°F) flow temperature.
So the pellet consumption should be higher at 50 degrees Celsius (122°F) than at 45 degrees Celsius (113°F) flow.
This would then affect the costs for the individual apartments, but not the numerical reading on the heat meter itself, since the basis for the calculation is different.

Am I understanding this correctly?
Thank you.

The heat quantity meters ultimately generate a distribution key, an index, to allocate the costs caused by the central heating system. It is therefore about the relationship between the measurement results. Absolute values are not relevant.

What a strange logic! The cost is actually allocated to you proportionally. More pellet consumption means higher costs, which are determined for you through the heat quantity meter.

rudiherbert schrieb:
Whether it’s 50 degrees or 45 degrees running through, 45 degrees would heat the room to the desired temperature just as well as 50 degrees. The flow rate should be the same amount, right????

The flow rate is naturally higher at 45°C (113°F) than at 50°C (122°F) if the room temperature is to remain the same.

A pellet boiler surely operates at a different internal temperature than the supply temperature, doesn’t it? This is controlled by a mixing valve.

Otherwise, what Alex85 and tomtom79 said is correct. All heating costs (pellets, maintenance, etc.) are calculated and then proportionally distributed among tenants, usually based on apartment size and consumption measurement. That is why the meters just need to “function equally,” but it doesn’t matter whether the meters measure kilowatt hours or apples and pears.

rudiherbert schrieb:
The heat meter only measures the flow rate in an active underfloor heating system. It doesn't matter if 50°C (122°F) or 45°C (113°F) flows through. The 45°C (113°F) would heat the room to the desired temperature just as well as the 50°C (122°F). The flow volume should be the same, right?

A heat meter measures the amount of heat ;-), not (just) the flow rate. It combines the flow measurement with the temperatures of the supply and return lines to calculate the heat delivered.

At the same output (room temperature), a higher supply temperature results either in a lower flow rate or a higher return temperature (or both). The amount of heat—and thus the cost allocation—does not change.

rudiherbert schrieb:
So the pellet consumption should be higher at 50°C (122°F) than at a supply temperature of 45°C (113°F).

I am not sure. Combustion systems can easily produce even higher supply temperatures. It is only condensing boilers, which also recover latent heat from the exhaust gases, that operate more efficiently at lower supply temperatures. So it depends on the system.