The most notable difference between heat pumps and air conditioners is that air conditioners only provide cold air, while heat pumps provide both a cooling and a heating mode. In cooling mode, heat pumps extract heat from the indoor air, release it, and then pump the newly cooled air back into your home. When outdoor temperatures drop, a reversing valve works to extract heat energy from the outside air (even in extremely cold temperatures) and pump hot air back into your home.