The cheapest and most energy-efficient form of heating in New Zealand is heat pump, giving 3.5 to 4.5 kilowatts of energy out for every kilowatt of energy that goes in. – What’s the most cost efficient heating for your home?
Heat pump is only designed to warm up or cool down one room. It is not designed for space more than the specific room. If purchasing more than two or three heat pump is an issue. Heat transfer system or heat transfer accessory of ventilation would be the cheapest option.