The difference between single stage, two stage, and fully modulating furnaces.

Stealth MediaJanuary 25, 2018
Revo Plumbing & Heating Infinity 90


Chances are if you have ever needed to replace or upgrade your furnace, you’ve heard these terms floated around. Along with terms like AFUE, MERV, CFM, DC or ECM motors and more, people can get confused. Confusion is never a good thing, it can get in your way of making the right decisions for yourself as well as your family. That is why our aim is to provide you with the base knowledge of the tangible differences between these 3 types of furnaces.

Single Stage Furnaces –

Contrary to popular belief, single stage furnaces can absolutely be the perfect fit for a family. A good way to think of furnaces is to that of a car with ‘gears’. A single stage has one gear, high. When it senses the call for heat from the thermostat, it ramps into high gear, heats until the desired temperature is met, then cuts out. This, for the most part, is good during the coldest months, but come warmer times it becomes a burden on your electrical needs. One of the biggest complaints with this type of heating is you may receive temperature swings.

Two Stage Furnaces –

A very popular type of furnace. Two-stage furnaces have two gears – low and high. The low stage runs on a lower capacity for longer periods of time. On average, your two stage furnace will only be running at high 25% of the time. This low setting is designed to distribute warm air more evenly, thus resulting in a more comfortable and consistent air. This low setting also helps to reduce energy costs because on warmer days it will stay on the low setting.

Fully Modulating Furnaces –

Fully modulating or variable speed furnaces don’t actually refer to the furnace itself, but rather the motor. The motor of the modulating furnace makes it able to increase in % increments. So instead of going from just low to high, you’re going from 25% to 30%, to 35%, back down to 30%, and so on. This is the most energy efficient type of furnace there is. And it is how we can have furnaces like the York YP9C which has an energy efficiency rating of 98%. With a York fully modulating furnace, your home will save the most money per month and also be as comfortable as possible when it comes to temperature in your home.

More questions? Call us today and we will be happy to answer any of them.