Variable speed delivers the precise amount of cooling or heating required for your desired temperature or humidity setting. This means you will have fewer temperature or humidity spikes to mitigate by adjusting your thermostat and initiating another cycle on your system. With a variable-speed compressor, the system has longer run times, reducing the number of starts and stops on your system. This change in how the system runs results in less wear and tear on the components because start-up and shutdown modes tend to be the hardest on the unit and reduced electricity consumption because usage surges when an HVAC system turns on. While longer run times might sound like increased energy costs, it is actually quite the opposite.
If the new unit has multiple stages, the system can run at a lower capacity stage to maintain your desired temperature. So unlike single-stage units that run at 100% all the time, a variable speed, multiple-stage unit can run at 20% power with the same effectiveness. According to a study by the Department of Energy, “Operating fan motors or compressors at lower speeds for longer periods can lead to reduced total energy consumption.”1 This is why air conditioners or heat pumps with compressors that can run at lower speeds for a longer period of time may actually use less energy than equipment with only one, 100% speed option.