To further ...
Plan is to install a heat pump of about 16-20 kW, air-water, as they can have an efficiency in the 5.8 COP level.
This means you get 5.8 times the heat vs the power you put in.
So a 4 kW max electrical load delivers upto 20 kW of heating / cooling.
I will keep the current oil heating system, but simply not use.
The oil bill last year was 3000 €, which will drop to essentially zero.
As an extra, I will get air-con throughout the very large 400m2 house and shop.
Estimated cost is around 8-10k€, for 14 fan-coil units (replace radiators).
Plus about 800 € in work hours.
I´m a contractor and these are my own import materials costs.
A commercial air-conditioning install of 20 kW would cost over 20 k€ (10-12 splits, give or take).
And because of the PV array, heating and aircon will be free, for now (30 years).
Saving about 3500€ in electric bills, and 3000 € in heating bills, per year.
And a 1000€ per year subsidy from the gov. for 4 years.