@a32 @yvan Problems with mobile A/C "monoblocks“ for heating:They often only work down to -5°C outside temp if at allhave a bad efficiency (SCOP ~3)also need a (big, 10-15 cm ø) hole in the wall (you don’t want to use these „open Windows" outlets)That's why we bought a standard split device. SCOP 4-5, works down to -15°C, hole in the wall has 5 cm ø, but the device outside is quite large. We noted though, that at outside temp <4°C it uses 2-3 times more power than above. Seems to be related to coolant, absorber size, defrosting, etc.Data so far and projection says our electricity bill will not be higher than before (wood pellets) at 0,39€/kWh el; ~500 €/a for 60 m^2 at comfortable 21-22°C.As for diesel heating or any similar CO/CO2 emitting devices, I’d be extremely careful indoors. You need proper exhaust ventilation (= hole in the wall) and alarm devices. If you have the means (chimney, space, money, etc), I'd suggest a pellet oven to at least avoid fossil fuels (the eco friendlyness of wood pellets is debatable, though). These ovens are also automatic.