When Herken started looking for an alternative to his gas heating system, he had already done more research than most.
His existing gas boiler was around ten years old and still working. So this wasn’t an emergency replacement.
Herken had time to understand the alternatives.
He compared different heat pump technologies and manufacturers. He looked at a Vaillant heat pump installed at a neighbouring home. And he wanted to understand what would make one approach more suitable than another.
What caught his attention about Adlår was something quite fundamental.
We weren’t asking one heat pump to do everything.
Instead, we proposed two purpose-specific heat pumps: an Aurora II for space heating and a separate Fjord for domestic hot water.
“I did a lot of research into the different solutions. I compared the Adlår system with my neighbour’s Vaillant installation and understood the benefit of having separate heat pumps for heating and hot water.”
A few months later, Herken would discover another benefit he hadn’t originally set out to find.
His heating system could also help keep the house more comfortable during hot summer weather.
Starting with the home
Herken lives with two other people in a three-bedroom, 188m² home with an EPC rating of D.
Before the change, a gas boiler supplied the home’s existing radiators, with an unvented cylinder providing hot water.
Rather than looking at the size of the old boiler and replacing it with an apparently equivalent heat pump, the new heating system was designed from the requirements of the home.
The calculated design heat loss was 5.4kW.
That led to an Aurora II 6kW being selected for space heating, alongside a separate Fjord 300L heat pump cylinder for domestic hot water.
This separation matters.
In a conventional single-heat-pump arrangement, the heat pump may need to switch away from space heating periodically to produce hotter water for the cylinder.
In Herken’s home, those two jobs have their own heat pumps.
The Aurora can concentrate on the temperature of the home while the Fjord independently looks after hot water.
For Herken, that was one of the differences that made sense when comparing systems.
Could the existing radiators stay?
This was one of the most interesting parts of the design.
Every existing radiator was retained.
There is a common assumption that installing a heat pump means replacing most — or even all — of the radiators in a home.
Herken’s house is a useful example of why that decision should be based on engineering rather than assumption.
Whether a radiator is suitable depends on how much heat its room requires, how much heat the radiator can provide and the temperature at which the heating system has been designed to operate.
In Herken’s case, the assessment showed that the existing radiators could remain as part of the proposed system.
The final heating design and operating flow temperature was set at 35°C.
That doesn’t mean every home can retain its existing radiators.
Some homes need larger emitters. Others may need changes in particular rooms.
The useful lesson from Herken’s home is simpler:
Don’t assume what needs replacing until you understand what the home needs.
It’s the same principle we use when sizing the heat pump itself.
From assessment to installation
The installation took place over 15 and 16 June 2026.
The Aurora was positioned behind the house, while the Fjord cylinder was installed in the garage.
One site-specific challenge involved routing pipework through an overhanging section of roof, requiring the installation team to work around the existing building layout.
Despite that, the complete installation was carried out over approximately one and a half working days and commissioned on 16 June.
The total contract value was £9,469.
Herken’s installation qualified for the £7,500 Boiler Upgrade Scheme grant, leaving a customer contribution of £1,969.
Those figures are specific to this installation. The cost of another heat pump system will depend on the home, its heating requirements, site-specific work, equipment and grant eligibility.
What was the system expected to cost to run?
Before installation, the system was modelled against the home’s calculated space-heating and hot-water requirements.
The design-stage estimate put combined annual heating and hot-water electricity consumption at approximately 4,809kWh, or around £1,202 a year using an electricity price of 25p/kWh.
But there’s an important distinction here.
Those aren’t Herken’s actual annual bills.
The system was only installed in June 2026, so it hasn’t yet operated through a complete heating season.
Actual energy use will depend on factors including winter weather, the temperatures maintained in the home, hot-water use, system settings and electricity tariff.
That makes the coming winter particularly interesting.
Once we have a complete heating season, we’ll be able to compare the original engineering model with the energy the system actually used.
For now, we think that’s a more useful distinction than presenting a design estimate as though it were an achieved saving.
Then Herken tried something we hadn’t installed the system primarily for
The Aurora is reversible, which means it can move heat in either direction.
During summer, Herken began experimenting.
Rather than adding air-conditioning units or dedicated cooling emitters, he circulated moderately cooled water through the home’s existing radiators.
And then he started measuring what happened.
“I have been experimenting with using my Adlår heat pump for cooling through the existing radiators, with no underfloor cooling, and the results have been much better than I expected.”
Using Home Assistant, Herken recorded approximately a month of data from his own system.
Over that period, he recorded 103kWh of electricity consumption and approximately 590kWh of heat removed from the home — equivalent to a customer-calculated seasonal EER of around 5.7.
But the numbers only tell part of the story.
What matters is what that cooling actually felt like.
Radiator cooling doesn’t feel like air conditioning
Herken is particularly clear about this.
“Radiator cooling behaves completely differently to air conditioning. It does not rapidly drop the room temperature. Instead, it slowly removes heat from the whole building and helps stop the house overheating in the first place.”
That’s an important distinction.
Air conditioning can deliver a concentrated stream of cold air and cool an individual room relatively quickly.
Cooling through radiators is gentler.
Instead of waiting until the house becomes very hot and then trying to rapidly cool it down, Herken found that the system worked better when started earlier, gradually limiting the amount of heat building up inside the home.
During his monitoring, he observed an indoor temperature difference of approximately 2°C with cooling operating.
During hotter August weather, the system wasn’t able to keep the entire 188m² home below 24°C.
And that’s worth saying.
This isn’t a story about radiators behaving like conventional air conditioning.
They don’t.
It’s a story about comfort cooling: gradually removing heat from the building, reducing heat build-up and helping the home recover overnight.
For Herken, that difference was noticeable.
What did the cooling cost?
On a typical cooling day, Herken recorded around 4kWh of electricity consumption.
He was able to use electricity charged into his home battery at an 8p/kWh cheap rate, giving him an effective electricity cost of around 32p for a typical cooling day.
That number needs context.
It’s Herken’s cost, based on his particular battery and electricity-tariff arrangement. It isn’t a standard cooling cost that another homeowner should expect.
At an electricity price of 25p/kWh, the same 4kWh of electricity would cost around £1.
That’s a good example of why we prefer to show the assumptions behind an energy-cost figure rather than present the most attractive number on its own.
There is an important technical consideration with radiator cooling
Herken also understood that circulating cool water through radiators isn’t simply a case of setting the heat pump as cold as possible.
If the surface temperature of radiators, valves or pipework falls below the dew point of the surrounding air, condensation can form.
Herken therefore configured his own dew-point protection through Home Assistant and experimented with cooling flow temperatures between 15°C and 18°C.
This is important because Herken’s setup shouldn’t be copied blindly.
His Home Assistant controls are his own configuration rather than a standard Adlår control feature, and appropriate cooling temperatures depend on factors including humidity, ventilation, pipe insulation and the materials within the heating system.
The broader principle is familiar:
More extreme settings aren’t automatically better.
Just as a heating system should be designed around the home, comfort cooling needs to operate within appropriate conditions too.
One system, two very different seasons
Herken originally chose the Adlår system because he had researched the available heat-pump options and saw value in separating space heating from domestic hot water.
The engineering assessment then established what his home needed.
A 6kW Aurora II was selected against a calculated 5.4kW design heat loss.
The existing radiators could stay.
The heating system was designed around a 35°C flow temperature.
A separate Fjord was installed for the household’s hot water.
And the installation was completed over approximately one and a half working days.
Then summer revealed another side to the system.
The same radiators that will keep the home warm through winter were able to gradually remove heat during hot weather.
Not like air conditioning.
Not instantly.
But enough for Herken to notice a meaningful difference to the comfort of his home.
That’s what makes this project particularly interesting.
It isn’t simply a heat-pump installation story.
It’s an example of what can become possible when the heating system is considered as a complete system around the home.
What happens next?
There’s an important chapter of Herken’s story we can’t write yet.
Winter.
The installation was completed in June 2026, so the system hasn’t yet generated a complete heating season of measured data.
Over the coming winter, the useful questions will be straightforward.
- Does the home remain comfortable during colder weather?
- How does the system perform as outside temperatures fall?
- How much electricity does space heating actually consume?
- How much energy does the Fjord use for hot water?
- And how do those real-world results compare with the calculations made before installation?
When a complete heating season is available, we’ll update Herken’s story with the results.
Because the best evidence of a heating-system design isn’t simply what the model predicts.
It’s what happens when people live with it.
Frequently asked questions
Can you use existing radiators with a heat pump?
Sometimes.
Whether existing radiators can remain depends on the heat requirement of individual rooms, the output available from each radiator and the flow temperature at which the heating system will operate.
All the existing radiators were retained in Herken’s home, but that shouldn’t be taken to mean radiator upgrades are unnecessary in every property. Each home needs to be assessed individually.
Can radiators cool a house with a heat pump?
A reversible heat pump can potentially circulate cooled water through suitable emitters, but radiator-based cooling behaves differently from conventional air conditioning.
In Herken’s home, it gradually removed heat and helped reduce overheating rather than rapidly cooling individual rooms. Cooling through water-based systems also requires careful management of condensation risk.
How long did Herken’s heat pump installation take?
Herken’s installation was completed over approximately one and a half working days in June 2026. Two engineers worked on the first day, with one returning for around half a day to complete the remaining work.
Installation time will vary according to the home and scope of work.
How much did Herken’s heat pump system cost?
The final contract value was £9,469. A £7,500 Boiler Upgrade Scheme grant reduced Herken’s customer contribution to £1,969.
Those figures are specific to his project and shouldn’t be treated as an indication that another home will have the same installation cost.
Every home tells us something different
Herken’s experience doesn’t tell us that every home can keep its existing radiators.
It doesn’t tell us that every homeowner will achieve the same energy use.
And it doesn’t mean radiator cooling will provide the same results in another building.
What it does demonstrate is why we start with the individual home.
Understand what it needs.
Design the system around it.
Then measure what happens when somebody actually lives with it.
That’s how engineering becomes comfort.
