Should I Get a Single‑Stage or Variable‑Speed AC?

Our South Carolina customers often ask this question, and the answer varies. If budget isn't the primary concern and you want a unit that delivers maximum comfort and the best energy efficiency, a variable-speed AC unit is almost always the answer.

However, variable-speed AC units are also at the top of the price range for home cooling, which can make them out of reach, depending on your budget.

When comparing variable speed vs. single speed HVAC options, we focus on the following:

This gives you a good idea of the pros and cons of variable-speed air conditioners and what to expect from a new unit.

A single-stage AC unit has only one speed, as the name implies. It's either on or off, with no way to control the amount of cooled air the unit produces. When your house heats up and the air conditioning kicks on, it runs at full capacity until the thermostat recognizes the right temperature, and then the unit shuts off completely.

While this makes your home cool quickly, it has some downsides. When looking at single-stage vs. variable-speed AC units, you'll notice that fast cooling also means inconsistent cooling, with some areas of your home needing to be cooler and others where you might be looking for a sweater. Variable speed gives you more consistent cooling throughout your home.

Full blast cooling also means you may pay more to keep your home cool due to higher energy costs. If your unit short cycles regularly, it can also mean higher maintenance costs.

If you're on a tight budget when it comes time to replace your air conditioner, a single-stage unit can get the job done, but it's rarely an ideal solution. But when comparing variable-speed HVAC vs. single-speed, you'll see many benefits from more control over your cooling.

Two-stage ACs are a type of variable-speed air conditioner that only has two settings. They can run at full capacity or on a low-power setting that is usually around 60% of the total cooling power of the unit. By offering more cooling control, you get better coverage and lower energy usage.

How? Since you don't always run the air conditioner at full blast, you aren't always using as much energy to cool your home. Plus, every time the AC turns on, it uses a big surge of power, which makes slower and steadier cooling a much more affordable option. Think of it like the difference in gas mileage from highway versus city. When you start and stop all the time, it takes more fuel than if you can just run at a steady pace.

Two-stage air conditioners are the mid-range when it comes to cooling. They have some of the benefits of variable speed air conditioners but a few drawbacks that also affect single-stage. Better cooling and lower energy costs don't mean the best cooling and the lowest energy use. For that, you'll need a true variable-speed air conditioner.

When looking at single-stage vs. variable-speed AC units, think of variable units as lights with dimmer switches versus simple on/off switches. A variable speed unit can use as much or as little power as needed to get your home to the desired temperature.

If it only needs to run at 20% power to drop the indoor temperature by 5-10 degrees, that's the amount of power it will use. You'll see the most savings from your variable speed unit during days when the temperature is warm but not sky-high.

Since these units can run at low speeds for the duration of time you need cooling, you get:

• More consistent cooling
• Top-notch dehumidification
• Lower energy bills
• Reduced maintenance costs
• More temperature precision

Variable speed units are the most energy-efficient of the three and most durable. You can expect one to last considerably longer than a comparable single-stage unit, though there are ways to get improved performance from a single-stage. If you install a variable speed air handler with a single-stage compressor, you'll see some boosts to energy efficiency and cooling capacity, even without a full variable speed control.

While single-stage units are the clear winner when it comes to price, how much does it actually cost for each type of cooling? In general, expect a single-stage to be the least expensive, a two-stage unit to be the mid-priced option, and a variable-speed to be the most expensive option.

Two-stage air conditioners typically cost about 30% more than a single stage, which can add $4,000 or more to your initial installation, though the total cost will depend on a variety of factors such as:

• SEER-rating
• Size
• Brand

In some cases, upgrading to a single-stage unit is only $500 more and offers significant operational savings over time. Variable-speed ACs can cost an additional $2,000 or more compared to a single-stage unit's price. Still, the energy efficiency of these units and possible tax rebates available often means you actually spend less.

When you're ready to upgrade, you'll want to find an installer to give you the right cooling at the right price. While discount installers exist, they rarely offer the security and long-term peace of mind you get with a qualified company. When looking for an HVAC company, make sure to find one that is:

• Licensed and insured
• Known for 5-star work
• Happy to offer a 100% satisfaction guarantee