TL;DR
SEER Ratings
13 SEER has the lowest upfront cost, 15 SEER is the best value for most Denver homes, 17 SEER adds quieter two-stage comfort, and 20 SEER gives the lowest monthly bills. The right level depends on how long you plan to stay, how hard your AC works, and your budget. MoJo's free price calculator shows all four side by side for your home.
When you price a new air conditioner, the first choice you'll face is the SEER rating. The MoJo HVAC price calculator lets you compare 13, 15, 17, and 20 SEER side by side for your home. This guide explains what each level really gets you, so you can choose the one that fits your home and your budget, not the one someone pushes.
What SEER Means in Plain Language
SEER (Seasonal Energy Efficiency Ratio) measures how much cooling an air conditioner delivers for each unit of electricity over a cooling season. A higher number means less electricity for the same cooling. Since 2023, new systems are tested under the updated SEER2 standard, so you may see both numbers on a quote. For more on the rating itself, see SEER2 ratings explained.
The Four Levels Side by Side
13 SEER (Standard): The federal-minimum tier, rated 13.4 SEER2 under today's test. It's single-stage, so it runs at full power whenever it's on. Reliable cooling at the lowest upfront cost.
15 SEER (High Efficiency): Uses roughly 13% less electricity than 13 SEER for the same cooling, with quieter operation. The best value for most homes.
17 SEER (Two-Stage Comfort): A two-stage compressor runs on a gentle low stage most of the day and switches to full power on the hottest afternoons. Roughly 24% less electricity than 13 SEER, quieter, with more even temperatures and better humidity control.
20 SEER (Premium Eco): A variable-speed compressor adjusts in small steps to match exactly what your home needs. Roughly 35% less electricity than 13 SEER, the lowest monthly bills, and the quietest, most even comfort.
What Those Numbers Mean in Denver
Efficiency savings grow with how much your AC runs. Denver summers are hot but shorter than in much of the country, and our dry air means an AC spends less effort pulling out humidity. That makes the payback on a premium unit slower here than in hotter, more humid places; we cover why Denver's climate changes the payback math in more detail. That's not a reason to skip efficiency. It's a reason to match the level to your home. A west-facing second floor that bakes every afternoon will feel the difference of a two-stage or variable-speed system far more than a shaded ranch home.
How to Choose
Choose 13 SEER if upfront cost matters most, you may move in a few years, or your AC only runs during the hottest weeks.
Choose 15 SEER if you want lower bills and quieter operation without paying for premium features. It's the sweet spot for most Denver homes.
Choose 17 SEER if comfort is the priority: rooms that run warm, an upstairs that never quite cools, or a household that notices noise.
Choose 20 SEER if you plan to stay for many years, run your AC a lot, and want the lowest bills and best comfort available.
Most homeowners land somewhere in the middle, and that's usually the right call. Without good information, it's easy to get pushed into a premium system you don't need, or to grab the cheapest option and live with the trade-offs for the next fifteen years. Our approach is to educate first and recommend second: explain the options plainly, then recommend what we would choose in your shoes.
Sizing Matters as Much as SEER
A high-SEER system that's the wrong size won't deliver what its rating promises. An oversized AC cools fast, shuts off, and leaves the air clammy and the temperatures uneven. The calculator sizes your system from your above-ground square footage and climate zone, and a MoJo technician confirms it on-site. Learn more in What Size AC or Furnace Does My Home Need?
See Your Price for Each Level
Select more than one SEER level in the MoJo HVAC price calculator and you'll see them side by side, with an estimated total and monthly payment for each. Prefer to talk it through? Call or text 720-807-4050 or contact our team. We'll answer every question and recommend what fits your home and budget, never more than you need.
Sources & References
U.S. Department of Energy - Central Air Conditioning, 2023
ENERGY STAR - Central Air Conditioners, 2024
Frequently Asked Questions
Is 13 SEER still allowed in Colorado?
Yes. New central air conditioners in Colorado must meet the federal minimum of 13.4 SEER2, and that is the level our 13 SEER tier is built to.
Does a higher SEER lower my heating bill?
No. SEER only measures cooling. Furnace efficiency is measured by AFUE, which we explain in our 80% vs 96% vs 97% furnace breakdown.
Is a 20 SEER air conditioner worth it in Denver?
It can be if you plan to stay many years and run your AC a lot, especially in a home that heats up in the afternoon. For many Denver homes, 15 or 17 SEER is the better value. We're happy to walk through the numbers for your home.
Why is a two-stage or variable-speed AC quieter?
Because it spends most of its time running at a lower speed instead of switching between full power and off. Lower speeds are quieter and keep temperatures more even from room to room.
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