The latest UK models from all the major manufactures. Air source heat pumps are a easy way of replacing a existing fossil fuel heating system. Off the gas grid locations are particularly expensive to run especially when oil is used and there is always a issue of a big oil tank which needs to be sited on the property which can be unsightly. Air source heat pumps have a outdoor condensing unit (heat collector) which collects the heat from the ambient air. These can be fixed on a wall or level and generally look exactly the same as a air conditioning system outdoor condensing unit.