The air source electric heat pumps system extracts heat from the air. It is electrically based, though it is relatively inexpensive to maintain price-wise compared to gas pumps. It is also easy to use, even for the average consumer. It is cleaner than a gas powered system and not as dangerous to run, since there is no flammable or asphyxiating fuel involved. These two factors have no doubt influenced the majority to choose air source electric pumps. However, there is a major disadvantage here. They are considered unhealthy for the environment, and systems are traditionally noisy (although some systems are said to be quiet performing). Most importantly, these systems lose their heating efficiency in extremely cold temperatures, as the COP (Coefficient of Performance) is greatly reduced.
Dual-Fuel Heat Pumps are air source electric heat pumps, except that they include a back up fuel system. The advantage here is that this system can help a great deal in the cold winter season. It is more economic than running electrical heat alone, and more efficient when it comes to heating the entire house. Since experts recommend having a backup system on file a dual system (that automatically switches back and forth according to temperature) would be an even better compromise. However, with the advantages of air source electric pumps and dual-fuel heat pumps also come the disadvantages of both.