This task is more accurately carried out by one of our qualified engineers; however, there are ‘rule of thumb’ guides to calculating heat-loads in residential applications. The size of the room, number of occupants, ambient temperature and the electronics heat loads are the factors which determine the size of the unit to be installed. Can the equipment heat as well as cool? It certainly can, and very efficiently too. The systems that heat as well as cool are referred to as ‘heat-pump’ systems. These systems are fitted with additional valves within the outdoor unit that can reverse the flow of the refrigerant cycle. In effect, the system then tries to cool the outside air, and rejects the heat which is collected (and amplified) to inside. The rated heating capacity of a ‘heat-pump’ system is generally slightly higher than its rated cooling capacity, and provides a huge saving in electrical consumption over any other form of electric heating. An electric fire, heater or under floor heating system that has a rated heating capacity of 3 kW, consumes a directly proportional 3 kW of electrical power. Some of the latest energy-efficient ‘inverter’ heat-pump systems can produce more than 5 kW of heat from 1 kW of electrical power, in turn providing an electrical saving of more than 80%.