Want Efficient AC? A Good SEER Is Not Sufficient

A Good SEER Is Not Sufficient If You Want an Efficient AC?

You need more than high SEER to get the most efficient air conditioning possible. There’s a mechanical side and a human side to an efficient AC.

SEER rating, if you’re wondering, is the seasonal efficiency ratio of an AC. It measures the ratio of cooling to how much energy is used to accomplish it. The higher the SEER, the more efficient the AC. But again, a good SEER is not the only factor that decides an efficient AC.

What is a Good SEER Rating for an Air Conditioner?

central air conditioner energy label

The easy answer is anything 16 SEER and above – all the way to 28 for standard split systems and 42 for mini split systems.

But the better answer is that it depends on your climate. The hotter the climate, the more cost-effective it is to choose a higher SEER. The unit will cost more, but in 3-10 years depending on your climate you will gain back the extra cost through lower energy bills.

You can use our SEER savings calculator to get a good SEER rating based on your location.  

Other Factors to Get the Highest Efficiency Apart From SEER Rating

OK, let’s start with the mechanical side – the equipment you choose. And then we can move to the human side – what role you play in getting the most efficient air conditioning possible.

Equipment – The Mechanics of High AC SEER

Air conditioners SEER performance is affected by these factors:

AC Size – In general, SEER rating goes down slightly as the AC size increases. For example, if you’re considering the Carrier Infinity 26 AC, it’s available in 4 sizes. Here they are with their SEER ratings according to the Energy Star Most Efficient AC list:

  • 2 ton – 25 SEER
  • 3 ton – 23.5 SEER
  • 4 ton – 21.5 SEER
  • 5 ton – 22 SEER

When the product page of an AC you are considering says it is “up to 25 SEER,” just keep in mind that is the top efficiency rating, and not every size will achieve it.

So what? The key here is this – make sure your HVAC technician properly sizes your air conditioner by doing a Manual J load calculation to determine exactly how many BTUs of cooling your home needs.

Tip: Base your AC comparisons on the right size unit for your home, not the most efficient AC in the range.

In the example above, buying the 5 ton Carrier Infinity 26 to get the higher SEER rating vs a 4 ton unit would waste energy, since the unit is bigger and consumes more energy overall. Plus, an oversized AC reduces dehumidification and temperature control, so your home won’t be as comfortable.

Consider 2 Stage and Variable Capacity ACs

Standard split systems come in 1 stage, 2 stage and modulating / variable capacity options.

Single stage ACs are up to 17 SEER. Two stage ACs are up to 21 SEER and variable capacity ACs are up to 28 SEER, though most are 20-24 SEER.

Research info: All mini split ACs have variable capacity compressors – but it’s called inverter technology in mini split systems. The effect is just about the same. And as noted, mini split ACs are up to 42 SEER!

Two stage and variable capacity ACs do not use as much energy to run most of the time. Two stage ACs have a low setting (about 65% capacity) and high (100%). Variable capacity ACs run as low as 25% or 40% depending on the brand. They will only use as much of their capacity as needed to maintain the temperature the thermostat is set to. So potentially, they use far less electricity. Single stage ACs run at 100% all the time – using maximum energy whenever they are running.  

Tip: Staged cooling is a big factor in higher SEER efficiency.

SEER is determined under very specific, controlled conditions. A 16 SEER single stage and 16 SEER 2 stage AC have the same peak efficiency. But because the 2 stage system will run on low much of the time, its overall efficiency performance in the “real world” will be better than the single stage unit that runs full blast all the time.

Use a Programmable or Smart Thermostat

This one is a blend of the equipment and the human side of AC efficiency.

Here is the point to consider: It is possible to cut energy use with a smart or programmable thermostat by adjusting the temperature setting throughout the day. Here’s a sample schedule:

  • 82F – From 8am to 5pm while you are at work
  • 74F – From 5pm to 10pm while you are home and awake
  • 78F – From 10pm to 8am until the next morning when you leave for work

You might like it cooler or warmer while you sleep, of course. But the point is that making those minor adjustments throughout the day can positively impact system efficiency. Set the thermostat temperature, and leave it alone.

A programmable thermostat will keep the temperature schedule you program it to follow. A smart thermostat like ecobee or nest will “learn” your temperature preferences and make the changes automatically.

Ecobee claims that “ecobee customers in North America saved up to 26% on their heating and cooling costs, based on an internal analysis…”

Some smart thermostats also have geofencing that automatically switches to and from Home and Away settings when you pass a geographical point you select. Plus, with their smart apps, you can adjust the temperature from anywhere. So, if the thermostat is going to change from 82 to 74 at 5pm, but you are staying out late that evening, you can change the time it adjusts to later in the evening and save energy while you are away.

Saving = More Efficient

Yes, that’s an “internal analysis,” not a third-party analysis, but still, we think you can definitely make your use of air conditioning more efficient with a smart thermostat if you make adjustments like shown in the schedule above. And once your smart thermostat learns the schedule, it will automatically make the adjustments.

Buy an Air Handler with an ECM Blower Motor

This is a minor part of the equation, so it doesn’t need a lot of discussion. Blower fans come in two types. PSC (permanent split capacitor) blowers are about 50% efficient. ECM (electronically commutated motor) motors are around 90% efficient – so they use less energy.

What You Can Do – Getting the Most Efficient AC in Practice

Let’s say you buy a car that’s a gas miser. Testing in a controlled environment shows it is capable of 36 miles per gallon.

But on the real-life road, you’ll have to drive at a reasonable speed, keep your tire pressure up and change the oil regularly. Fail in those steps, and your MPG will suffer. It’s similar with the human side of efficient air conditioning.

We’ve already discussed making sure the AC is the right size and choosing a smart or programmable thermostat. Here are more tips that depend on you for AC efficiency.

Keep the HVAC System Maintained

Dirt is the nemesis of efficiency. So, whether you do it yourself, hire an HVAC company or a mix of both, follow at minimum this checklist.

Keep your filter clean by replacement or washing. This is DIY. Check it monthly, and replace or clean it as needed. Some thermostats have a Dirty Filter notification too, so if you like reminders, look for one like those from Lux, nest, Bosch and most other brands.

Clean the outside and inside coils every year or two depending on how heavily your AC runs. If you have a heat pump that heats and cools, the coils get dirty faster, so more frequent maintenance is required. DIY or pro.

Complete full maintenance service every 1-3 years depending on how frequently the system runs. This is a pro option. A certified HVAC technician will go through a checklist of 15-30 items to ensure your HVAC system is cleaned, tuned, lubed if needed and fully charged with refrigerant. It’s the best way to ensure peak efficiency.

Make sure ductwork is sealed and insulated. The Energy Star website says, “about 20 to 30 percent of the air that moves through the duct system is lost due to leaks, holes, and poorly connected ducts.”  Up to 30 cents of every dollar you spend on cooling and heating your home is lost??? That could be the case.

That’s a lot of cash blown into a basement or attic where it isn’t doing your living space any good.

This can be DIY if you use the right materials and techniques to insulate your ducts. Tutorial videos are available showing how to insulate various types of ductwork.

Meet R-value Recommendations for Insulation

Properly insulate your home. The US Department of Energy identifies 6 major areas where your home should be insulated – from the foundation to the attic, windows and doors, etc. A well-insulated home is an efficient home – and the savings will show up every month on your energy bill.

Don’t Buy a SEER Rating that is Too High

What? Isn’t that contrary to what we’ve been saying? Yes and no.

If your goal is to cool your home with AC as efficiently as possible for eco-friendly living, then sure, buy the most efficient AC you can afford.

But if your goal is buying a cost-effective system, then it is possible to overdo it on SEER. Think about it this way: If you spend $1,500 extra on a super-efficient, variable capacity AC, you might never recoup the higher cost if you live in a moderate or cool zone of the country.

The key is to get written estimates from several experienced pros that can recommend the right efficiency and performance (single stage, 2 stage, variable capacity) for your climate and home. A 14 SEER, single stage AC is cheap, but install that in Arizona or Louisiana, and your energy costs would be astronomical. On the other hand, a 24 SEER AC is really expensive, and in Maine or Minnesota, you would never save enough to make up for the higher cost. A good AC contractor can help you find the efficiency and cost-effective sweet spot for your situation.

There is an optimal cooling efficiency and AC performance for every house. Use our Free Local Quotes tool to get the best recommendations for an air conditioning system for your climate and your home. And once it is installed – or until you buy a new AC – follow the suggestions in this guide for AC efficiency beyond just the SEER rating.

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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