What’s The Deal With Modulating Furnaces?

It's easy to assume that a furnace is just a furnace, but there are plenty of different furnaces that offer unique advantages and drawbacks in terms of performance and efficiency. A modulating furnace is one of the several different types of furnaces available that offer unique performance benefits. The following explains how these furnaces work as well as its advantages and drawbacks:

Variable Speeds for Better Performance

The major benefit behind a modulating furnace is its ability to modulate its performance based on what your home needs at that moment. This is possible thanks to a couple of innovative features that aren't commonly found in other furnaces. The first is a gas valve that increases or decreases in the flame in fine increments to prevent broad variations in target temperature.

The second feature is a variable speed blower fan that can also be adjusted in fine increments. For example, a variable speed blower can slowly ramp itself up on startup to reduce noise and mechanical shock. During periods of low heating demand, the blower can operate at low speed to maintain air circulation without drastically affecting room temperatures.

How They Compare Against Single and Dual-Stage Furnaces

A typical modulating furnace usually offers drastically better performance in terms of heating and energy efficiency than comparable single-stage or dual stage furnaces. This is largely due to the flexibility of the modulating furnace in comparison with its less-advanced counterparts:

  • Single-stage furnaces use gas valves that operate fully open or fully closed and blower fans that only run at a single speed. This means that a single-stage furnace has to constantly run and shut itself off in a never-ending balancing act to maintain comfortable temperatures.
  • Dual-stage furnaces are capable of running at a "high" setting as well as a "low" setting, but these settings still lack the flexibility that a modulating furnace offers.

Potential Downsides

There are only a couple of downsides to having a modulating furnace. The first involves the initial purchase price - modulating furnaces typically cost more than their single or dual-stage counterparts. According to home remodeling expert Lee Wallender, a typical modulating furnace with a 98-percent AFUE rating may cost anywhere from $5,000 to $6,000.

Another downside is that you might not be able to recoup those costs as quickly as you'd think. Despite their energy efficiency and resulting low energy costs, it could take several years before you start seeing any real cost savings. This makes a modulating furnace a long-term investment for your home.
