Single Stage vs Two Stage Furnace – Differences + How they Work

You need a furnace to create a comfortable indoor climate during winter or cold days. However, the level of comfort you get will depend on the heating technology of your unit. Between a single stage and two stage furnace, let’s find out which one is a perfect fit for your home’s heating, ventilation and air conditioning system.

A furnace is a device used for heating air for warmth in homes and commercial buildings. Older versions of furnaces were powered by wood and coal but today’s models run on gas, propane or electricity to produce heat. A furnace comes in two categories; single stage and two stage furnace.

A single stage furnace operates on a single mode of heat output. This model is either off or on and running at full capacity. Two stage furnace on the other hand operates at varied power modes for low or high heat output. This provides efficient heating for colder and mild days.

Single Stage vs Two Stage Furnace – Difference

Choosing the right type of furnace for your HVAC system comes with many benefits that include low running costs, consistent comfort and improved indoor air quality. If you are about to invest in a furnace for your home or office heating, the following difference between a single stage and two stage furnace will help you make an informed decision.

Single Stage FurnaceTwo Stage Furnace
TechnologyHas a fixed fuel valve and single-speed blower fan motorComes with a multi-speed blower fan motor and valve with two stage settings
Comfort There is inconsistent in heat output which creates warm and cold spots.Has a consistent heat output that makes a home very comfortable
EfficiencyRuns on full power throughout even when low heat is needed thus leading to high power pillsRuns on low setting to effectively meet most house heat demand thus saves a lot of energy
Noise levelThe single speed blower motor produces some noise  Operates quietly without making producing noise especially at lower fan speed
DurabilityHighly durable model with less cases of regular breakdownsHigher cases of the heater breaking down frequently are reported
CostThis air heating unit cost less expensive to purchase but costly to run due to higher billsCost more expensive to purchase but saves on energy bills
MaintenanceDoes not break down easily and also cost less to do repairsIt may cost more to carry out a repairs occasioned by frequent technical issues
Single Stage vs Two Stage Furnace

Why you should choose a Two Stage Furnace

A single stage furnace has its advantages that include low purchase price and less technical issues but it is expensive to run due to its inability to conserve energy. On the other hand, purchasing a two stage furnace may cost you a tooth and nail but this will quickly be recouped in lower running costs. The following are more reasons you should choose a two stage furnace.

  • Creates a more comfortable indoor climate: Two stage furnace provides a steady flow of warm air that keeps indoor temperatures consistent without any warm and cold spots.
  • Conserves energy use thus lower cost of bills: A two stage furnace runs on lower power settings most of the time producing longer cycles of heat. This not only creates consistent comfort but also conserves energy which translates to lower energy bills.
  • Improves indoor air quality: Furnaces are not only meant for air heating, but also filtering and circulating air into a building. A two stage furnace allows air enough time for all the polluting particles to be trapped by the system’s filters.
  • Two-stage furnace runs quietly: It is hard to notice when a two stage furnace is running especially on the lower fan speed. This makes it peaceful to enjoy your time in home or your office.
  • Cheaper in the long run: While the purchase cost may seem higher, this will eventually be recouped by lower running costs that are brought by conservation of energy.

How does a Two Stage Furnace Work?

One-stage and two stage concept of a furnace originates from the burner section of the unit and the settings on the valve that controls the flow of propane or natural gas. One stage furnace has a valve that only opens to allow full combustion of the fuel and closes to stop it completely.

The valve in a two stage heating furnace is equipped with one more setting for low and full heat output. Once powered on, a two stage furnace will run at 70 or 80% of its full rated capacity. This is adequate enough to meet household heating demands 80% of the time.

On a very cold day or when you want to manually increase the internal temperature of your home, a two stage furnace will automatically fire up second stage burners to a full output. This will continue until when the most consistent comfort level in a home is achieved.

Most furnaces use a simple timer to control the firing up of second stage. So if the air in your home doesn’t reach the set temperature within 10 minutes, the timer automatically triggers on the second stage burning. Full heating is also activated if the thermostat senses that it needs to raise the temperature.

Final Thought

Apart from the above differences, your choice for a single stage or two furnace may be influenced by your area climate, the size of your home, budget and most important your personal preference. Before you completely decide, it is good you talk to an HVAC professional who can come up with the best recommendation for a furnace that will befit your comfort needs.