Straight cool systems are great for homeowners that almost never turn their heat on. It costs less up front and is more efficient on the cooling side, but costs more to use in heat mode than a heat pump system might. Straight cool systems are air conditioning units with a built-in heating element for space heating – also known as heat strips. When you turn your straight cool system on heating, you’ll spend three to four times more whenever you run the heat with your AC system.