One of the most cost-effective alternatives to both liquid-based and high-mass space heating systems is an air-based installation. This is because the equipment used is relatively cheap and simple, and the transfer medium has no special requirements. Air-based systems cannot be used to heat a domestic water supply, but work well for space heating.

Contrary to what you might expect, air-based systems are very popular in climates where the heating requirement is high. They can produce impressive amounts of hot air on cold, sunny winter days, especially if there is snow on the ground, dumping the gathered energy into the home through a ducting system. Air collectors are usually vertically wall-mounted and are cheaper than liquid-based collectors, although they can produce the same number of Btus per square foot.

On the down-side, air-based systems need a substantial blower to push the hot air around the ducts, which means they eat a lot of power. Even in an efficient home, the blower can account for as much as half of a home's cold-season electricity requirement.

The biggest disadvantage, apart from the electricity use, is that air-based installations are always dump systems. They cannot use storage. Historically, a load of different storage mediums have been tried – everything from special tubes filled with eutectic salts to a cupboard full of bricks – but none of them were reliable in the long term. In some cases, the storage worked great, but air quality suffered as the storage medium accumulated mold, humidity, dust and all sort of other nastiness. In other cases, the storage medium just corroded its way out of where it was kept. Scratch any ideas of having a dedicated storage setup immediately!

There are two types of air-based solar thermal space heating installations , both of which need some specialized equipment to operate efficiently.