Furnaces burn oil or gas to generate heat, while heat pumps run on electricity, drawing heat/energy from outside air (even cold air) or ground and transferring it indoors. Because of how they work, the heat pump is more energy-effective with very little CO2 emissions, while an oil or gas furnace could make very high temperatures quickly and easily. But are so inefficient and cause great damage to the environment; we feel the consequences of this every day.