The letters in HVAC stand for heating, ventilation and air conditioning. An HVAC system enables you to regulate your home or building’s internal temperature (thermal control) for comfortable living and working. You can bring heat levels down in the summer and up in the winter, keeping your home or office livable year-round. HVAC systems can also help with humidity levels and regulate indoor air quality in a home or office. There are many types of HVAC systems and technologies available.

Many homes have a forced-air HVAC system. Both the heating and the central air conditioning units share a ductwork system where they either push in or pull out warm or cooled air. There are also heating and cooling systems that don’t require ductwork — such as ductless mini-splits — but work on the same principles of heat exchange. The national average to hire an HVAC specialist is $2,920-$3,670, with costs varying depending on the work you need done and the equipment you are installing.

If your furnace needs to be repaired, you’ll want to find a qualified heating, ventilating and air conditioning (HVAC) repair technician. Each state has its own licensing requirements; some require all HVAC technicians to have an HVAC license, while others only require someone operating an HVAC service and installation company with employees to hold a contractor’s license. For example, in Alabama, the Alabama Board of Heating Air Conditioning, and Refrigeration Contractors regulates licensing, while in Kansas there is no state regulatory body and HVAC licensing can vary by region. For simple furnace repairs like changing out a filter, a trusted handyman can probably handle the job, but a trained professional should be hired for tasks like replacing a gas valve, installing a new inducer fan motor or other critical furnace repair jobs that involve dealing with gas leaks or other dangerous conditions. For more, check out our tips for smart hiring on Thumbtack.

The national average for furnace replacement is between $1,800 and $2,500. The cost can range dramatically higher depending on the model of furnace you select, any repair work you require, your location and the cost of installation. Furnace installation costs can be more than the furnace itself due to the cost of doing business and the expertise needed to install the HVAC equipment. Installing a new furnace generally requires technical know-how and the proper tools and licensing. It’s best to hire a pro and budget for furnace installation rather than risk potentially unsafe DIY installation. This will ensure your home’s safety. Check to see if your HVAC contractor has the proper licensing to do the job. If you need duct repair or replacement, expect to pay more for your furnace installation costs. The price for duct repair could be an hourly rate ranging on average anywhere from $85 to $150 per hour, with additional costs for parts.

Heating typically constitutes 42 percent of a homeowner’s utility bill, according to Energy.gov. If your heating bills are through the roof, it might be time to compare what you’re spending on utility bills to the cost of a new furnace. A new furnace can cost between $1,000 and $2,700 for standard big-box forced-air furnaces, and more than $10,000 for advanced technology or high-end brands.

With a new furnace you could lower your total energy bill by 30 percent while also reducing your carbon footprint. To achieve these savings, Energy.gov recommends combining proper equipment maintenance, insulation, air sealing, strategic thermostat settings, and — of course — energy-efficient HVAC equipment. The furnace cost you’re facing may seem large upfront, but should save you money in the long term with improved home heating at a lower cost. Furnace cost is dictated by brand, efficiency, technology and the British thermal units (BTUs) needed to heat your home. AFUE is another important acronym. It’s short for annual fuel utilization efficiency, and it represents what percentage of the fuel becomes heat for the home. Energy.gov explains that an AFUE of 90 percent means 90 percent of the energy in the fuel is used to heat the home, and the other 10 percent escapes.

The number of years an HVAC system lasts depend on the type and brand of components that make up your system. The lifespan of an air conditioner averages between 15 and 20 years. The life expectancy of a tankless water heater is approximately 20 years, while a storage water heater is closer to 10-15 years. Ducts may need replacing within 10-15 years. Your equipment will have a longer life if you have regular tuneups and maintenance to keep everything in good working order. If you’re having repair problems and your HVAC system is over 10 years old, it’s a good time to consider the costs and benefits of repairing vs. replacing. Energystar.gov provides the following tips to help you decide whether to repair or replace:

• Your HVAC system needs frequent repairs and your energy bills are increasing.
• Your cooling or heating equipment is less efficient.
• Rooms in your home are too hot or too cold.
• Your heat pump or air conditioner is more than 10 years old.
• Replacing your system with an Energy Star-certified unit could save up to 20 percent on your heating and cooling bills.
• Your furnace or boiler is more than 15 years old.
• You may choose to replace your system with an Energy Star-certified furnace (which is 15 percent more efficient than a conventional furnace) or an Energy Star-certified boiler (which is 5 percent more efficient).
• Your home has humidity problems.
• Your home has excessive dust.
• Leaky ducts can pull particles and air from attics, crawl spaces and basements and distribute them throughout your house. Sealing your ducts may be a solution.
• Your heating or cooling system is noisy.
• You could have an undersized duct system or a problem with the indoor coil of your cooling equipment.
• Your score on the Home Energy Yardstick is below five.
• That means your home energy use is above average and you're probably paying too much for your utilities.