For 30 years? I thought he had converted the house from oil?
In any case, €1,200 electricity costs with that area, the age of the property (only 10cm insulation), 25 degrees, and use of radiators is not feasible.
That is about 4,500 kWh electricity consumption.
Go to the heat pump consumption database. There you will find real numbers – usually new builds (excerpt for 2019 and area over 200 sqm below / some consumption is extremely low if the system was only put into operation during 2019). The
To my knowledge, that would be a mistake. How am I doing with my assumption of 15 cm stone + 8 cm ETICS as the structure of the 23 cm exterior wall? - 13 cm interior wall would not be possible with any stone known to me. 12.5 might still be possible depending on the manufacturer with aerated concrete.
It was a former night storage heater house that I now want to equip with radiators and am considering between two heat generators.
An acquaintance has been doing this for over 30 years with a heat pump and radiators. He says he has 25°C in winter on 400m/2 and costs of around 1200€.