Quote for 7kw Vaillant - surely not enough?

[Michael_S]

So we had the £250 Heat Geek survey.  They have come back with a proposal for a 7kw Vaillant heat pump (apparently they only do Vaillant under this offer)

 

Their heat loss calc says that at the reference temp (-2.7 here) the heat loss is 7.83kw.  I know this is about accurate and our rads support this at a flow temp of about 45C

 

WE heat our hot water by immersion and use of order 24kwh per day.  There is no proposal to change the tank so lets assume that at the -2.7C day the cop on hot water is only 2. That means another 0.5kw of heat energy needed on average taking it to 8.23kw.  And that is before there is any thought about recovering an overnight setback or other unexpected heat loss (power cut, windows open for painting or whatever).

 

Too me the 7kw sounds under powered, are there any charts for its output at different air and flow temps to suggest that it would be powerful enough? 

 

What would people think would be the correct size heat pump for this heat requirement - I think we need a unit that provides 9 or 10kw at -2.7 air / 45 flow.

 

Thanks