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Hi PH & welcome to the forum.

The main thing to appreciate is that there’s a whole world of difference between the 8 and the 9kW Daikins. It’s not just a 1kW extra.

Daikin make 2 HP chassis, a small one (4,6,8 kW) and a big one 9,11,16kW)

Your choice here is whether you get a big chassis or a small one.

I spent about 9 months persuading Octopus that they should install an 8kW at my house when they wanted to install an 11kW. The major difference is in how much the HP can turn down to a minimum output on days when maximum output is not needed (ie most of the time).

The problem with having a higher minimum output is that a) you need to supply a higher minimum electrical input and b) you need to find something to do with all the heat that you don’t need.

Do a search on the forums and you’ll find plenty of threads from folk who have had their large Daikins replaced with smaller ones and are much more satisfied.

Bottom line is: get the smallest HP that will cover your real-world heat loss - which may well be lower than your MCS calculated heat loss.

Cheers, David

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