How to replace your air conditioner

Keep cool without blowing your budget

Hot fun in the summer?

Even the hardiest heat lovers need a break from high temperatures and wilting humidity.

Of course, air conditioning can help, and a lot of us rely on it. According to the U.S. Census Bureau's American Housing Survey, 64% of U.S. households have central air. Another 10% use some form of room unit.

If your AC breaks, though, misery awaits. And if you let an older unit limp along, you could be tossing money out the window.

How do you know when the time is right to upgrade the way you cool your home? A lot of different factors come into play, including what kind of unit you already have and the replacement cost.

Before you open your wallet, there are seven questions you should ask yourself to determine the best option for you and your budget.

Replace or repair?

Even though the typical lifespan of a central air unit is 15 to 20 years, if your unit is more than 10 years old, you may want to consider replacement, according to Energy Star, the government-backed program that promotes energy efficiency.

That's because a new, high-efficiency unit can save you up to 20% on your cooling costs.

Other signals your AC could be past its prime: If your home is too humid in the summer, you're calling a repair person every year or the unit is noisy.

On the other hand, if you're seeing more dust in your home when the unit is on, or that some rooms are too hot or too cold, the problem could be in the ducts or with your insulation — problems that can be fixed without replacing the unit.

Either way, an HVAC specialist can do an assessment and tell you what repairs can be made to cool your home more efficiently, whether it's replacing the unit or fixing another problem.

How much efficiency is enough?

Air-conditioning units are graded on the SEER scale, which stands for seasonal energy efficiency ratio. The higher the number, the more efficient the unit.

The lowest rating allowed for units sold in this country is 13. The highest rating is 30.

Most efficient units hit the mid- to high 20s.

Air-conditioning systems must have a SEER rating of at least 14 to be considered for the Energy Star program.

The Washington, D.C.-based American Council for an Energy Efficient Economy recommends units with at least a SEER rating of 14.5-15.0 if you live in a warm climate.

Energy Star units can cost an additional $300 to $2,000 more than comparable conventional models, depending on the size of the unit your house needs. In all, you can expect to pay several thousand dollars for a typical replacement unit, according to Consumer Reports.

For that additional up-front cash, you'll save money on your energy bills, up to $200 annually depending on where you live, according to the U.S. Department of Energy.

What are my savings?

If you're on the fence about whether to repair or replace, calculating your energy savings can help you make the call. Same thing if you're waffling between a conventional or Energy Star unit.

So how to make that call? Energy Star has a calculator to help you out. Follow the "Savings Calculator (Excel)" link on the right side of the page.

The calculator takes into account where you live, the type of unit you have and your electricity rate (you can find that on your electric bill) to determine both your current annual and life-cycle costs and what you'd spend if you replaced your unit.

It'll even let you know how long it'll take for the unit to pay for itself through savings in your electricity bill.

If you're still unsure, check with Energy Star to see what rebates are available where you live. You also can ask your utility company if it has rebate offers.

What is the best unit for me?

The size of your home will help determine what kind of unit you'll need, but there are other factors to consider.

"The same house with windows on the south side versus the north side could make a huge difference, for example," says Rob Capri, an HVAC expert with Gault Energy, a Connecticut-based company.

Getting the right-size unit is important, too. But bigger isn't always better.

"If a unit is too small, it will not cool the house down enough to the desired temperature," Capri says. "It would continuously run in hot weather, making it more costly to operate."

If it's too large, the house will cool down fast, but the humidity will stay behind.

An HVAC contractor can help you determine if replacing your unit is necessary and what size unit would fit your home.

Who should do this work?

While size and efficiency are certainly important, who you hire to install your unit is your biggest decision.

Try the Air Conditioning Contractors of America’s search tool.

Look for contractors who are NATE-certified; the North American Technician Excellence designation means they have passed tests demonstrating real-world HVAC knowledge.

Make sure the contractor is licensed, insured and bonded, and has been in business for many years. You want someone who will be there to service and repair your unit and honor the labor warranty.

A good contractor will perform an analysis of your home based on square footage, ventilation, windows and insulation before giving you an estimate or recommending an air conditioner.

The labor estimate should include installation; any adjustments to ducting, venting or electrical systems; and disposal.

The contractor should provide details about recommended brand, size, efficiency and parts warranty, as well as operating costs.

Get comprehensive, written quotes that leave no room for surprises from at least three contractors.

What are the other options?

Central air doesn't work for everyone, especially if you live in a house that doesn't have forced heat.

One option is a ductless system, which comes with a slim indoor unit with a fan (usually installed on or near the ceiling), and a compressor unit, which is installed outside.

These systems are ideal for ductless homes, or if you're trying to add air to one space, like a room over a garage. Expect to pay at least $4,000 per unit installed.

Another choice is high-velocity air conditioning.

"It's a really good option for people who have an established house with boilers," says Phil Rizzo, HVAC instructor at Chicago's Coyne College.

High-velocity systems circulate cold air into a room through 2- to 3-inch flexible tubing, which is snaked through the walls and/or ceilings of your home. Then the air is pumped out through nozzles in the corner or ceiling of the room.

Pricing is by the ton. The average home needs 2.5 tons, and each ton can cost $5,000 to $6,000.

What about a window unit?

If you don't want to cut holes into your walls, window units can be an easy way to add air to a room. They have the cheapest up-front cost. You can buy window units at just about any big-box hardware store for less than $150.

But they're not perfect. They're heavy, and their weight can damage windowsills. They're also loud and not very efficient.

Still, window units can be ideal if you just want to cool down a bedroom at night, or you're in a smaller home that doesn't need much cooling.

You may also see portable units while you're searching for window units. They're the same thing, except that instead of hanging out a window, they sit on the floor, and you hook a hose up to the outside environment. They also usually cost more  — from $300 to $700 each.

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