When you drive your car on a freeway with a speed limit of 65 MPH most people don’t put the gas-pedal all the way to the floor until they hit 75 then shut their engine off until they get back down to 55 then start the engine and throttle it, running the engine at full capacity until they hit 75 again. Of course not. Such behavior would wear out your car pretty quick, waste a lot of gas and make your passengers crazy. But that’s pretty much the way single- and two-stage HVAC systems work.
ASHRAE Says 100% Just 5% of the Time
A variable-speed HVAC system, on the other-hand, will quickly take your environment to the proper temperature and then apply just enough “throttle” to keep it there providing an extra layer of home comfort while saving you money on your electric bill.
The home rarely needs its HVAC equipment to run at 100 percent capacity. In fact, climatic weather data from the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) shows that, on average, most locations in the United States see the need for 100 percent capacity less than 5 percent of the year. A variable-speed unit can determine when a home does not require full capacity and can adjust to provide incremental operation.
Variable Speed Plus Zoning
When installed with a zoning system, a variable-speed system can recognize that the majority of the house is perfectly cool, with the exception of that one room (or zone). The unit will then change its operation to run at a lower percentage of capacity and cool only that particular zone, thus saving energy by running at a lower speed while keeping that bedroom as cool as the rest of the house.
Another advantage to variable-speed equipment is that it can more effectively control humidity levels in the home. A variable-speed heat pump is running optimally when it cools a home at a lower capacity during a longer cycle. This low and steady approach allows the heat pump to remove more moisture from the air, since the cycle is longer and more consistent. Plus, a home with less humidity feels cooler than a more humid home, which can also allow the homeowner to keep the thermostat at a higher setting during the warm summer months.
Feed the piggy bank
You’d be right if you were thinking that a system this smart will save you money. By knowing when to operate at lower speeds, a variable-speed system automatically (or as we like to say, “Auto-magically”) runs more efficiently saving you money every month on your energy bill.
So overall what you can expect from a variable speed system over a single- or double-stage system is the elimination of full-blast, short cycles, leading to more consistent home temperatures, better humidity control, longer motor life, a quieter system and lower monthly energy bills.