New types of space heating being suggested via grants

Hi everyone,
just wondered if anyone has a hybrid heat pump or a microwave boiler - these were suggested to us by the grant scheme instead of an airsource heat pump, which we have been refused owing to not having wall insulation.
The information I have so far about the hybrid heat pump is that it will run on 70% air source and 30% gas in colder months. The model I have been asked to consider is the Daikin Altherma Hybrid air to water gas condensing heat pump.

As for microwave boilers , I haven’t heard of these before, but came across this link,Wayv%20boilers%20don%E2%80%99t%20emit%20carbon%20into%20the%20atmosphere.

Obviously, like every other householder trying to decarbonize and decrease their energy consumption, while preventing their bills from sharply increasing - I have lots more questions than I started with on my retrofit journey.
These new developments and possibilities are all very interesting , but it feels wise to wait for more information on performance.

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I am suspicious of microwave boilers, primarily as a simple resistive heater (think of a kettle) is already turning 100% of the electrical energy into heat. A microwave heater seems just a more complicated way to still just heat water.
The article appears to contradict itself too - "cost the consumer … same to run as a gas boiler.” Later in the article it says: “microwave boilers would need a lot of power. This would mean upgrading the wiring in many homes. And as electricity can be 4-5 times more expensive than natural gas”

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I don’t have a hybrid boiler but have spoken with someone who has one. He tells me that without the RHI it would be very expensive to run.

There is also a system that has the two units in one Murelle Revolution 30 - SIME : SIME. This was used by Wales and West and WPD to trial the use of hybrid systems to reduce CO2. While that works they concluded it was not economic to run compared with current gas boilers.


Thankyou so much for your feedback here - I appreciate it so much You are worth your weight in gold.

I have said this before and I’m saying again
For a householder such as myself, who is typical in their limited understanding of new technology for home energy systems and in understanding retrofit ,
the value of your feedback and the information you share here is huge.

This forum is highly representing for it’s members and really shines a guiding light on all things retrofit and home energy.


Thanks again everyone.

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Late to the conversation.

My understanding is that any boiler/water heating device and any heat pump can be run concurrently as a hybrid system. Simply plumb in the heat pump first in line and then the outflow from the heat pump becomes the inflow for the other heating system. The second system only kicks in if it’s inflow temperature falls below its desired outflow temperature.
You could even retain your old system and add an affordable heat pump.

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Would I need a separate temperature monitoring device to tell the gas when to turn on?.

Central heating boilers measure incoming water temperature anyway. The pump circulates the water all the time you have the heating on but the boiler goes on and off depending on the return temperature.
If you use the boiler for instant hot water then I don’t know how that would work. I think it might depend on make and model of boiler. I suspect that it might assume cold incoming water.

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Thanks for your feedback Tim. It’s very much appreciated.
I just posted an update on our progress in the green grants thread…not even deserving of being called progress really :grimacing: