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What Size AC Unit Is Right For My Home?

An AC system is a big investment that requires a well-informed homeowner, and we know you want to make all the right decisions for your home. Big Mountain Heating & Air is here to share our knowledge and make sure your AC replacement goes flawlessly and performs perfectly for your home.

How Does Size Affect Your AC Performance?

Most homeowners know there are different sizes of AC systems, but it’s also important to know how size can actually affect the AC’s efficiency. 

If your AC is too small it won’t be able to keep up with the demand of your household. Therefore, it will struggle for most of the day to regulate the air temperature. An AC that runs that much is using a huge amount of energy, and you’ll see it reflected in your utility bill. 

Overcompensating isn’t a great idea either. If the AC is too large for the space then it will cool too quickly. Once it has cooled the air to the desired temperature it will shut off and the air will begin to warm again. This causes frequent starting and stopping of the system, which you’ll still see in your energy bill. 

Also, your AC system is meant to filter and dehumidify as well as cool air. If the system does the job too quickly, your air won’t have time to be filtered of contaminants and moisture. This can be dangerous for long periods of time – especially for people with respiratory sensitivity.

How To Calculate Your Ideal AC Size

When you’re ready to figure out the appropriate sized AC unit for your home there are a couple of ways you can go about it. 

Use HVAC Expertise

Calling on an experienced HVAC team like Big Mountain Heating & Air can save you a lot of hassle. Plus, our team uses a comprehensive system to determine the best size AC for your home based on a long list of factors.

  • Living area volume
  • Natural shade provided
  • Sun exposure
  • Window details – condition, age, number, orientation 
  • Home age
  • Insulation and sealing
  • Established ventilation or ductwork 

If you’d like to get ahead of the game and have a professional calculate the right size AC for your home, contact us! We make it easier than you thought possible to get your answer and feel confident when buying your new AC system.

DIY Sizing

If you’d like to size your own AC unit you can do that as well! There is an equation you can use to calculate a rough estimate of your home’s needs and the resulting AC unit match. 

First, it’s important to note two key terms when understanding AC sizes.

  • BTUs – BTUs are the energy required to cool the air in your home. According to your home size there is a specific BTU demand for your home.
  • Tons – No, not the actual weight of the unit! Tons refer to how many BTUs the unit uses to cool. For example, one ton is equal to 12,000 BTUs.

So, to find the required tonnage, you must also calculate the required BTUs with this equation: (Sq. ft. X 25 BTU)/ 12,000 BTU


What size AC do I need for a 1,500 square foot home?

(1,500 sq. ft. X 25 BTU)/ 12,000 BTU = 3.1

This customer would need either a 3 ton or 3.5 ton unit.

Remember: This estimate can still be affected by other factors in your home, so the most accurate sizing is still done by HVAC professionals. 

Need Professional AC Sizing?

If you’re planning an AC installation in Sacramento don’t hesitate to contact Big Mountain Heating & Air to help you through the process. From sizes to SEER ratings to a flawless installation, we’re the team you can count on!

We Want You As A Customer For Life

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Our team of expert technicians is ready to help with professionalism and high-quality workmanship.
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HVAC services can be a big investment, which is why we offer flexible financing options to help you pay for services when you need them most.
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There's no room for rudeness in customer service. Our team will help you find the best solution for your home.

What Our Customers Have To Say

Good Rebates

This is a review for a complete HVAC system replacement from Big Mountain. I started at the SMUD website looking for the best rebate program and found a list of contractors there. I vetted out companies that had a lower number of completed jobs per the SMUD rebate program data.

Lee S.

Very Professional

Had my A/C go out yesterday, called Big Mountain today and they had a serviceman in my area of Lincoln, he was here within a half hour and fix my unit in a very professional manner, and the cost was reasonable. I was very impressed with the company and the serviceman.

Tom D.


I had a appointment with them between 1-3 and one of their staff members called me and kept me updated when they will arrive which was nice. Steve arrived on time and was really nice for explaining what could the cause be. My ac fan was working but cool air wasn’t coming out.

Krystal L.