If you have started researching heat pumps, you have probably come across the term flow temperature. It sounds technical, but the idea behind it is simple, and it has more influence on your running costs than almost anything else in your heating system.
What Flow Temperature Actually Means
Flow temperature is the temperature of the water your heating system sends out to your radiators or underfloor heating. A traditional gas boiler often runs at 70°C to 80°C, heating the water quickly and hard before shutting off again.
An air source heat pump works differently. It gathers heat from the outside air and raises it to a useful temperature using a compressor, then circulates that warmth around your home. Because it is moving heat rather than burning fuel, it performs best when it is asked to produce water at a gentler temperature over a longer period.
Why Lower Flow Temperatures Suit Heat Pumps
The smaller the gap between the outside air temperature and the flow temperature, the less work the compressor has to do. Less work means less electricity, and less electricity means lower bills.
This is why manufacturers quote their best efficiency figures at 35°C. Both the Grant Aerona range and the Vaillant aroTHERM Plus units we install achieve an A+++ ERP rating at a 35°C flow temperature. We design our systems to target a 400% SCOP, which is only realistic when the system is set up to run at sensible flow temperatures.
How to Run Your Home at a Lower Flow Temperature
Lower flow temperatures need a system designed around them. That usually involves:
- Correctly sized radiators, which are often larger than the ones fitted for a boiler
- Underfloor heating, which spreads warmth across a wide surface area
- Good insulation, so the heat you generate stays where you want it
- Steady, continuous running rather than short bursts of heating
Will My Home Still Be Warm?
Yes. A well-designed system keeps your rooms at the temperature you set. The heat simply arrives more gradually and stays more consistent through the day.
Hot water is handled separately through a cylinder, and the AROtherm Plus can deliver a 75°C flow temperature when hot water demand calls for it.
Getting the Design Right from the Start
Flow temperature is decided at the design stage, not afterwards. During our site survey we assess your property properly so the system we specify performs the way it should.
Call us on 0208 936 7639 or book a free consultation with one of our engineers.
