The Goldilocks secret to great heat pump results
- Mark Thompson
- Jan 27
- 3 min read
Updated: 2 days ago
For the full list of articles demystifying heat pumps click here
The secret: just the "right" radiator temperature
(No, it’s not a secret button hidden behind the sofa.)
We all expect to be at a comfortable temperature in a car in winter. We expect the car heater to give us warmer air in very cold days that we do on milder days.
A house is no different.
The colder it is outside, the more heat it will need to keep a home comfortable indoors. The easiest and most comfortable way to do that in a house is to vary the temperature of the radiators to suit the weather: hotter radiators when the weather is coldest.
When setup properly heat pumps can do this very easily and efficiently.
Heat pumps have a sensor that tells them the temperature outside. They can use this knowledge to work out what is "just" the right temperature water to send to the rads.
Just like the porridge in the Goldilocks story - the perfect radiator temperature for "todays weather".
No hotter than needed, no cooler than needed. Just enough heat to going in to keep the house at the temperature you want.
The right radiator temperature "for the weather"
If it is allowed to work in this way, a heat pump gives you hotter radiators in cold weather and radiators that are not as hot in milder weather.
This link between outdoor temperature and radiator temperature is called weather compensation. This is the only jargon I can’t avoid using. My apologies!
It is a well proven way to setup a heat pump for maximum efficiency. The problem is that there are many heat pumps in the UK that are not set up to work like this.
For folk that like graphs, this shows how weather compensation works. Hottest rads in colder weather. Not so hot in warmer weather.
Sometimes weather compensation is called:
A heat curve
A compensation curve
Water law
Weather Dependent Curve (or WD Curve)
They all mean the same thing.
This is a very good, short and jargon free video explaining this subject
Most heat pumps are not being allowed to do this
Sadly, most heat pumps aren't currently setup in this way. The best kept secret though, is that they CAN actually all do it.
The reason they aren't setup in the right way is because most installers fit timers and thermostats to give households familiar controls. Familiar yes. Efficient no.
As you'll have read in the last article, thermostats and timers are generally bad news for heat pump efficiency.
The good news is that this is usually fixable without any plumbing work or physical changing the heating system. It is just about controlling a heat pump in a different way that we are used to.
It is straightforward to change over to using a heat pump in weather compensation mode. It means:
Changing some very specific heat pump settings
Learning some new habits
"Giving control" of the heating to the heat pump by almost entirely stopping the use of thermostats and schedulers.
It takes a little experimentation to get the "Goldilocks" settings right for the individual household.
Low and slow. Just the right radiator temperature for todays weather....to provide...just the right level of comfort.
The next few articles and practical guides have been written to give you confidence that you make the necessary changes, so you can tame your own heat pump.
Using a heat pump in this way can cause unnecessary worry
This variation in radiator temperature day to day can cause concern sometimes. Someone might touch a radiator and feel it is only barely warm or not as warm as other times. They may then think something is wrong.
This is usually fine, and perfectly normal. In milder weather radiators simply don’t need to be very hot. It’s just the heat pump doing its thing, making sure it is as efficient is possible.
Next: Article 7: Taming your own heat pump
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Thanks.
Mark Thompson
Get Energy Savvy - simple practical home energy efficiency information
Good morning Mark,
Really helpful and I love the way your articles are written in such a user-friendly way – thank you!
We have an AUX heat pump and have tried using the weather compensation mode, however the house was just getting too hot even on the lowest setting. I think the biggest problem for us was at night time when we like a cool house but were constantly having to throw the (summer!) duvet off even with the windows open.
We have gone back to using the Settings like a boiler, which I know we shouldn’t, but I don’t know how else to get around this – any pointers?
Thank you so much, Helen
Thank you Mark this is excellent! I've never understood weather compensation before but now can support my daughter with her heat pump settings, though will still need to try to understand what role there may still be for different settings different times of day if she's out of the house or to benefit from times of cheaper electricity maybe... Thank you again for this excellent clear illuminating interesting article! And looking forward to the Daikin information next month. Nicola