Different HVAC styles can improve comfort and efficiency. (Photo: Dreamstime/TNS).

September is an excellent time to take stock of your HVAC system before the cool season begins in earnest. If nothing else, you should change your filters and hire a pro to inspect and tune up your system, at a cost of around $80 to $100, before turning your heater on.

However, if you’re ready to make a big investment, this is also a good time to think about upgrading your system with zoned, multistage or smart systems. These improvements make a big difference in energy efficiency and comfort, but they do carry a significant price tag.

What is a zoned HVAC system?

Zoned HVAC systems activate based on areas of use, which is much more efficient than heating or cooling the entire house with a single central system. These systems include different thermostats for each zone, all of which are operated from an overall control panel. This way, you can keep your bedroom cooler while increasing the temperature in areas you rarely use.

A series of automatic dampers in the ducts shunt hot or cold around the house according to need. This increases comfort and improves energy efficiency. You’ll spend less money to heat or cool your bedroom and living room, for instance, while applying less energy to other areas of the house.

The cost of the system depends on how extensively you separate zones. Many such systems have just two zones – upstairs and downstairs, which will cost you about $2,500 to install. The cost goes up when you add more zones.

How can multistage HVAC help me?

A multistage heating and air conditioning system adds flexibility and comfort to your home. Traditional one-stage systems have two speeds: on and off. When the thermostat detects the need to change temperature, it activates and pumps hot or cold air at full blast into the home envelope until the temperature reaches the desired level.

This one-size-fits-all approach does a good job of changing temperature, but it’s not the ideal method of creating a comfortable climate. A multistage system, also known as a variable-speed or two-stage system, adds comfort and increases efficiency without sacrificing effectiveness.

Instead of cycling on and off during the day, a variable-speed heater or air conditioner will activate at its highest stage of power early in the day to quickly bring the home to ideal temperature. Once it reaches that setting, the system drops down to a less powerful stage that runs continuously to keep the temperature stable. This consumes less energy, adds less wear and tear to the system, usually creates less noise and keeps the air constantly moving, which helps with air quality. It also prevents the stop-and-start feel of single-stage systems, and more effectively controls humidity.

However, on average, this upgrade adds about 30 percent to an HVAC system’s cost, and usually has to be added as part of a full heater or A/C replacement. Retrofitting an existing system to a multi-stage is generally unwieldy and expensive; in most cases, you might as well replace the whole thing.

By Paul F. P. Pogue, Angie’s List. Paul  is a reporter for Angie’s List, a trusted provider of local consumer reviews and an online marketplace of services from top-rated providers. Visit AngiesList.com.