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4 Terms to Know When Choosing an AC Unit | C.B. Lucas

Posted On: September 13, 2018

When you’re shopping for a new AC unit, you may wonder what all the number and letters mean and how you can choose the best unit for you. You’ll need to know how to decipher the terms used to describe different products, especially if you want to find a high-performance or eco-friendly unit. Here are four terms you need to know if you’re shopping for a unit.

1. BTU

BTU stands for British thermal units, a measurement of how much cooling power your unit has. This number can help identify the correct size of AC unit for cooling your house. In general, you’re likely to need about 25 BTU of cooling power per square foot in your house.

In some cases, you’ll simply need to buy a unit with the same BTU rating as the one you already had. However, if your old unit couldn’t keep up with the cooling or if you’ve added on to the house in any way that can add to the AC burden, you may need a larger unit.

Have a contractor come to your house and calculate the number of BTU that you’ll need. They can help you avoid ending up with an undersized or oversized unit, which could mean wasting energy and even wearing out your unit sooner.


The Seasonal Energy Efficiency Ratio, or SEER, is calculated by dividing your unit’s BTU by how much energy it uses. If you’re looking for an efficient unit, you need to be looking for higher SEER numbers. The minimum allowed in the US is 14, so you can get better efficiency by choosing a higher SEER number; they go all the way up to 21 for typical AC systems.

You can get higher efficiency with alternative HVAC systems, such as geothermal, but those typically require a large investment and a considerable amount of excavation.


If you’ve shopped for appliances, windows, or other home maintenance and improvement items recently, you may have come across the ENERGY STAR certification before. This certification is an EPA program that’s designed to let consumers know which products can be trusted to perform in an energy-efficient manner.

For items that use electricity, such as AC units, ENERGY STAR certification indicates (among other things) that the model uses energy in an efficient way. Products must be independently tested and meet the criteria before they’re eligible. Keep in mind that this certification only means the product is efficient, not that it’s necessarily the most eco-friendly overall.

For example, if you want to reduce your AC’s impact on the environment as much as possible, you can look for a company with responsible manufacturing practices or one that gives back to the rainforest. You can also improve eco-friendliness after installation; for example, remove your unit’s reliance on fossil fuels by installing a solar panel to power it.

Buying ENERGY STAR–certified products doesn’t just mean you’ll save money on energy bills. You may also be able to find money-back programs such as rebates from your electrical company or local government, or even state or federal tax credits, depending on where you live and what products you’re buying.

4. R-22 and R-410A

R-22 is the coolant that was used in AC units but isn’t manufactured for sale in the US anymore. Modern-day AC units typically use R-410A, which has replaced the other coolant because it’s considered less damaging to the environment. However, these refrigerants aren’t interchangeable in the same unit, meaning you have to get a new one to use the eco-friendly option.

These four terms can help you read technical specs about AC products and actually get something out of it. Whether you need help and guidance in choosing a unit or just need an expert professional installation, get in touch with C.B. Lucas today.

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