Ground source heat pumps (GSHPs) are generally the most efficient, achieving 350-500% efficiency by leveraging stable underground temperatures, though they have higher installation costs. Air source heat pumps (ASHPs) are also highly efficient at 250-400%, extracting heat from the air, but their performance can be affected by extreme outdoor temperatures. In contrast, a traditional gas boiler for heating is around 90-95% efficient, while separate air conditioning units cool, but neither offers the combined, high-efficiency performance of a heat pump. Therefore, for overall energy savings and reduced environmental impact, heat pumps are the superior choice for both heating and cooling.