Lets try and add some logic!
A Hybrid system’s goal, is to provide around 80% of your heating all year round or continue to do so through a mild winter. ASHP’s can potentially work in temperatures as low as -25c however, a ASHP has to work harder to heat your home below a certain threshold, typically below 0c reducing their efficiency, which is where a Hybrid system comes into play.
Most ASHP output an average of 45c, older homes especially lack the building envelope insulation of new homes being built today, will struggle more to keep the warmth in homes. This is further impacted by your location (the further north you get), along with the fact older homes have smaller radiators for traditional gas or oil fired boilers, which aren’t adequately sized for ASHP’s.
The advantage of a Hybrid setup especially in your case, as you can answer yes to the above paragraph, is you will beable to fall back on your boiler, when conditions don’t allow a heat pump to provide the warmth you require, especially as heat pumps struggle and become less efficient below 0c. There is another overlooked advantage of a Hybrid system, which is as we get older we start to feel the cold more, therefore having a Hybrid system allows you to take advantage of such a setup.
Sizing wise there isn’t much difference between a full ASHP system or a Hybrid one, because all a Hybrid system does is take advantage when the weather drops below a certain threshold, where a full ASHP would start to struggle and become less efficient. AsI have said before there are plenty of ways to get a guestimate on size require but, only one proper way and if you still have the measurements from doing the Heatpunk calculation why not do the MCS official one and see if they differ and if so by how much!
Once you are happy the sizing is correct, you can use that to gain quotes, but don’t tell the installer! Let them come to their own conclusion and if its near what you have in your head, you know the installer is on the ball park of what should be installed. Telling them what they should know/do may prove detrimental as you could loose MCS protection if something wasn’t right and the installer wrote on his sheet “customer specified” or words to that effect. By doing this if they fit a system to small to cope or to big it cycled it is the installers responsibility to put right through the MCS scheme! This does not stop you suggesting you want xyz make heat pump, solar, battery etc.
One last word weather compensation, whether implimitated or as a kit are important in the overall efficiency and running costs. If you are asked if you want it fitted or turned off or on, if standard, you should be saying yes you want it and yes turn it on in the first instance.
Enough waffle for this post, but you are 100% doing the right thing having a Hybrit system 🙂