9kw Heat pump? thats a large heat loss, is there no way you are able to reduce the heat loss of the property, its always the best route to go regardless of how you heat the home?
Or it could be a larger than average sized house in a northern location.
From this reply I take you don’t have any experience in thermal calculations and modern building.
The thermal envelope of the property heat loss has zero relevance to the location or size of the property.