> solar PV installed cost 384 €/kWp

Is this grid-scale solar ? It can’t be rooftop - there is nobody in the UK who will install a 5kW rooftop system for £2k. The quotes I’ve had recently have been closer to £10k.

Yes. It literally says:

> The cost assumptions assume utility-scale solar panels and batteries in large parks. Smaller-scale rooftop solar and home batteries would cost 2-3 times more.

I've installed domestic solar several times. The main cost isn't the panels or the inverters - it's the scaffolding, labour, and wiring improvements in the home. If you have a tall or complicated house, it'll cost more.