Energy efficiency isn’t just a “nice to have” for through-the-wall air conditioners—it’s the single biggest factor affecting your comfort, electricity bills, and environmental impact.
In 2025, the best through-the-wall AC units aren’t just cooling workhorses—they’re precision machines designed to squeeze the most comfort out of every watt. But if you don’t understand EER, CEER, and Energy Star ratings, you risk overspending on electricity or buying a unit that underperforms.
This guide will show you:
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How EER and CEER are calculated (and why they matter)
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How to use efficiency ratings to compare models
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What Energy Star certification means in real-world savings
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How to calculate your annual operating cost
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Which features improve efficiency beyond the label
By the end, you’ll know how to shop smart, cut your energy costs, and stay cool—Savvy style.
2. What Is EER (Energy Efficiency Ratio)?
Definition:
EER stands for Energy Efficiency Ratio. It measures the cooling capacity of an AC unit (in BTUs) divided by its electrical input (in watts) under a standard test condition—usually at an outdoor temperature of 95°F.
Formula:
EER = Cooling Capacity (BTUs) ÷ Power Input (Watts)
Example:
If an AC has a 12,000 BTU capacity and draws 1,200 watts:
Why it matters:
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Higher EER = greater efficiency (more cooling for the same electricity).
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EER is a snapshot—it shows efficiency under specific, high-temperature test conditions.
Typical ranges for through-the-wall ACs in 2025:
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Standard models: 9.0–10.5 EER
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High-efficiency models: 10.6–12.0+ EER
3. What Is CEER (Combined Energy Efficiency Ratio)?
Definition:
CEER stands for Combined Energy Efficiency Ratio. It’s the modern version of EER that factors in standby and off-mode power consumption.
Why it’s more realistic:
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Even when your AC isn’t actively cooling, it can draw power (for sensors, displays, or Wi-Fi).
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CEER measures overall efficiency, so it better predicts your actual electric bill.
Formula:
Example:
Two 12,000 BTU units with the same EER might differ in CEER if one uses less standby power. Over time, that difference can add up.
Typical ranges for through-the-wall ACs in 2025:
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Standard: 9.0–10.0 CEER
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High-efficiency: 10.1–11.5+ CEER
4. What Is the Energy Star Program?
Overview:
Energy Star is a government-backed certification that identifies products meeting strict energy efficiency guidelines.
For through-the-wall ACs in 2025:
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Minimum EER: 10.7 (varies by capacity)
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Must meet CEER standards for standby efficiency.
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Tested and verified by third parties.
Benefits of Energy Star units:
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Use ~10% less energy than standard models.
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Often qualify for utility rebates and tax credits.
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Lower lifetime operating costs.
💡 Savvy tip: Check your local utility’s rebate page—some offer $50–$150 back on qualifying models.
5. EER & CEER Benchmarks for Through-the-Wall Units
| Unit Size (BTUs) | Good EER | Excellent EER | Good CEER | Excellent CEER |
|---|---|---|---|---|
| 8,000–10,000 | 10.0 | 11.5+ | 9.5 | 10.5+ |
| 12,000–14,000 | 9.8 | 11.0+ | 9.2 | 10.2+ |
| 15,000–18,000 | 9.5 | 10.8+ | 9.0 | 10.0+ |
Rule of thumb: The larger the BTU capacity, the harder it is to maintain very high efficiency—so compare ratings within your size category.
6. Factors That Affect Real-World Efficiency
a. Sizing
If your BTU rating is too high, the AC will short-cycle, running inefficiently and failing to dehumidify. Too low, and it will run constantly, burning electricity without cooling enough.
b. Installation Quality
Through-the-wall ACs must be sealed tightly in their wall sleeve. Even a small gap can waste cooled air and force the unit to work harder.
c. Maintenance
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Dirty filters reduce airflow, making the unit less efficient.
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Dusty coils reduce heat transfer efficiency.
d. Climate
Units in hot, humid climates run longer and consume more energy—even with the same EER rating.
7. Calculating the Annual Cost of Operation
Step 1: Find your unit’s wattage
Example:
12,000 BTUs ÷ 10.0 EER = 1,200 watts
Step 2: Estimate usage hours
Let’s say 8 hours/day for 90 days = 720 hours
Step 3: Multiply by your local electricity rate
If your rate is $0.15/kWh:
💡 Savvy tip: Compare two units—one with EER 10.0 vs. 11.5—and see the yearly difference. Over 10 years, it’s often hundreds of dollars.
8. High-Efficiency Features to Look For
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Programmable thermostat: Adjusts automatically to avoid wasted cooling.
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Variable-speed fans/inverter technology: Runs at lower speeds for longer, maintaining steady comfort with less energy.
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Wi-Fi/smart controls: Let you turn the AC off when away and on before you return.
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Sleep/eco mode: Lowers output when you’re inactive or sleeping.
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Filter alert system: Reminds you to clean/replace filters for peak efficiency.
9. Comparing Models: Efficiency vs. Price
Example:
Model A: 12,000 BTU, EER 10.0, $550
Model B: 12,000 BTU, EER 11.5, $650
Annual cost difference (based on earlier calculation):
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Model A: $129.60/year
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Model B: $112.70/year
Savings/year = $16.90 → Over 10 years: $169
In this case, the $100 price difference pays for itself in ~6 years—plus you get better efficiency and possibly a quieter, higher-quality unit.
10. Savvy’s Efficiency Checklist
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Check EER & CEER ratings—aim for the top of your BTU category.
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Look for the Energy Star label—guarantees minimum efficiency standards.
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Review estimated annual operating cost on the yellow EnergyGuide label.
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Factor in installation quality—poor sealing will erase efficiency gains.
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Consider usage patterns—smart features may save more for frequent users.
11. Common Misconceptions
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“Bigger BTU units are always less efficient.”
Not always—some large units have excellent ratings, but they’re rare and cost more. -
“Energy Star is always the most efficient option.”
It’s the minimum standard for high efficiency—many units exceed it. -
“All AC types are rated the same way.”
Through-the-wall units, window ACs, and mini-splits each have different performance benchmarks.
12. Final Recommendations & Next Steps
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For long-term savings: Aim for EER ≥ 10.5 and CEER ≥ 10.0 in your size category.
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If on a budget: Even moving from an EER of 9.5 to 10.0 can yield meaningful savings over time.
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Don’t forget rebates: Check local incentives before buying.
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Installation & maintenance matter: The most efficient unit won’t deliver if poorly installed or neglected.
In the Next topic we will read more about: Can Through-the-Wall AC Units Provide Heat in the Winter?
