Your air conditioner should have about 20 BTU per square foot of living space, according to Consumer Reports. However, you should also account for other factors in the room. 

If it’s a very shady space, you can take off 10% of the square footage BTU calculation. If it’s sunny, add 10%. For rooms normally occupied by two or more people, you should add 600 BTU per additional person. Finally, if the room is a kitchen, add 4,000 BTU to your calculated square footage total.

Talk to an air conditioning company or HVAC professional to find out what size you should get.

The SEER label on an air conditioner stands for seasonal energy efficiency ratio. This is a measure of the efficiency of either an air conditioning unit or a heat pump. 

The U.S. Department of Energy recommends replacing older AC units with energy-efficient models. Contact an air conditioning company or HVAC specialist for tips on how to select a new unit.

Installing a new appliance costs $125, on average. However, homeowners should expect to pay within the range of $120 to $150. 

For less complex appliance installations, you may pay a low-end cost ranging between $65 and $100. On the other hand, more complex appliances like laundry machines, ranges and other items can cost between $175 and $326 to install. Ask whichever appliance installation service you hire to give you a price quote, if possible.

You can tip appliance installers if you feel their service has gone above and beyond. A standard tip is between $10 and $20. 

Reasons you might consider tipping include a very pleasant customer service demeanor, having to carry a heavy appliance up or down the stairs, working in inclement weather, taking care not to make a mess and other acts of care and consideration. You are not obligated to leave a tip — but one is always appreciated.

There are a number of different appliances that professionals can install for you, including:

• Washers and dryers. These machines are heavy and very sensitive to being level and balanced, and also require hookups to water, electricity and sometimes gas or propane.
• Cooking ranges. Your range may use propane or gas, which is a hookup job best left to the pros.
• Microwaves. You may want to have your microwave be an undermount or in-mounted unit, which a pro can install and make it look seamless.
• Refrigerators. These are heavy and often require a water hookup.
• And more!

Reach out to an appliance installation service, and find out if they can install your appliance. Often, it’s helpful to provide the brand and model of the appliance you’re trying to set up.

There are several perks to having a professional install your appliances, including:

• Hiring a pro saves you time and money. If it breaks down, the service person who sold and installed the machine can fulfill its warranty. However, this warranty could be void if you install it incorrectly.
• It will work reliably. Many appliances like ranges and laundry machines rely on being on level surfaces as well as having potentially dangerous hookups installed correctly. 
• You can get repair and maintenance support. If something isn’t working or you want advice, you can call up your installer and ask if they can help you troubleshoot or repair it.

Prices for central-air HVAC systems will vary. The national average to hire an HVAC specialist is $2,920-$3,670 but can run as high as $5,000 or even $12,000 depending on the capacity you need and other factors. Installing central air conditioning requires an entire system that works together to draw hot air out of your home. The system includes an outdoor unit, which houses the condenser and compressor, and the evaporator coils. If you don’t have an existing duct system, ductwork will need to be installed, which will affect labor and material costs. Leaking or damaged ducts will also need to be replaced.

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 AC system is in need of replacement, the national average air conditioner installation costs range from $2,930 to $3,670. Costs can vary greatly depending on whether you are replacing a wall or window unit or a central air system. A central air system is connected to ductwork that runs throughout your house and pumps cooled air into your various rooms via vents and registers. A central air conditioning system is far more costly than wall or window units. Selecting a central AC system that has a high seasonal energy-efficiency ratio (SEER) will likely lower both your carbon footprint and your utility bill. The type of AC system you select, where you live in the country, and the regional costs of HVAC work, duct removal and replacement, and ductwork repairs that are needed are some of the main factors that affect the cost of new air conditioner installation. Here are some examples of average costs for installing forced-air systems.

• Install Lennox 16 SEER single-stage AC unit: $5,743
• Removing and disposing of the old furnace, moving and reconnecting the water heater, and installing a 3.5-ton gas furnace. The job took 18 hours of labor.

• Installation of a new 14 SEER single-range cooling system: $4,000-$6,000
• Installation of a new 16 SEER two-range cooling system: $6,000-$8,000
• Installation of a new 20 SEER variable capacity cooling system: $8,000-$12,000

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.