Introduction: The Evolving World of Water Heater Efficiency Ratings
When shopping for a new gas water heater, especially a large model like the State ProLine 74-Gallon High Capacity Atmospheric Vent Gas Water Heater, you may encounter terms like Energy Factor (EF) and Uniform Energy Factor (UEF). Understanding these ratings is crucial for making an informed, cost-effective, and environmentally responsible purchase.
In this guide, we’ll explore:
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What EF and UEF mean
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Why the industry shifted from EF to UEF
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How these ratings impact your utility bills
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How the State ProLine model performs on efficiency scales
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Verified external resources for continued learning
🔍 What Is Energy Factor (EF)?
🌊 The Original Efficiency Metric
Energy Factor (EF) was the traditional metric used by the U.S. Department of Energy (DOE) to measure water heater efficiency. It considers:
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Recovery efficiency (how efficiently heat is transferred to water)
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Standby losses (how much heat escapes from the tank when not in use)
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Cycling losses (energy lost as water circulates in the tank)
As defined by Energy.gov, EF was historically used for decades before UEF became the standard.
🌟 Interpreting EF Scores
An EF rating ranges from 0.50 (low efficiency) to about 0.90+ (high efficiency for tank models). For standard atmospheric vent gas water heaters:
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Typical EF: 0.55 to 0.62
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High-efficiency non-condensing: 0.65 to 0.70
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Condensing units: 0.80 to 0.95+
The State ProLine 74-gallon atmospheric vent model typically had an EF rating around 0.60 under this system.
🤖 Why EF Was Replaced by UEF
🔄 The Problem with EF Ratings
While EF was useful, it had weaknesses:
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Test procedures didn’t reflect real-world usage patterns
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Didn’t differentiate between household sizes
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Inconsistent results across manufacturers
🔧 Enter Uniform Energy Factor (UEF)
In 2017, the DOE introduced Uniform Energy Factor (UEF) to provide a more accurate, consumer-friendly measurement.
According to AHRI, UEF offers better performance comparisons between different water heaters.
🔄 How UEF Is Calculated
UEF incorporates:
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Actual hot water usage profiles (small, medium, large, extra-large households)
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Energy used per gallon of hot water delivered
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Realistic draw patterns over 24-hour test cycles
📊 UEF Rating Categories
| Household Size | Test Profile | Daily Water Use |
|---|---|---|
| Very Small | 10 gallons | S |
| Low | 38 gallons | M |
| Average | 55 gallons | L |
| High | 84 gallons | XL |
For a 74-gallon model like the State ProLine, the test typically uses the XL profile.
Full details on testing protocols can be found via the DOE Testing Procedures (10 CFR Part 430).
🌟 Comparing EF and UEF: A Simple Translation
While not directly convertible, here’s a rough approximation:
| EF (Old System) | UEF (New System) |
| 0.55 | ~0.58 |
| 0.60 | ~0.62 |
| 0.65 | ~0.67 |
| 0.70 | ~0.72 |
The State ProLine 74-Gallon model with its former EF of ~0.60 typically lands around UEF 0.60-0.62.
See side-by-side efficiency ratings via the AHRI Directory.
🌪️ Why UEF Is More Helpful for Homeowners
🧳 Reflects Real-Life Usage
UEF accounts for variations in daily hot water use, making ratings far more relatable.
🌍 Easier for Comparison Shopping
UEF allows consumers to confidently compare different sizes, brands, and technologies.
💸 More Transparency for Incentives
Utility rebates, federal tax credits, and Energy Star qualifications now use UEF for eligibility.
Check available rebates via Energy Star Rebate Finder.
📈 The Financial Impact of UEF on Energy Costs
🔢 How Efficiency Affects Annual Operating Cost
According to Energy.gov:
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Each 0.1 improvement in UEF can save $15-$35 annually (depending on gas prices and usage).
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Over a 10-year lifespan, this could equal $150-$350 in energy savings.
💲 Break-Even Analysis for Upgrading Efficiency
| UEF | Annual Cost (Avg) | 10-Year Savings |
| 0.60 | ~$380 | $0 |
| 0.70 | ~$340 | $400 |
| 0.80 | ~$300 | $800 |
| 0.90 | ~$270 | $1,100 |
These calculations assume $1.25/therm gas cost, average 5-person household.
🏢 Where the State ProLine 74-Gallon Model Fits
The State ProLine High Capacity Atmospheric Vent 74-Gallon Gas Water Heater:
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UEF ~0.60 (standard non-condensing tank efficiency)
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Qualifies for some state rebates but often below federal tax credit thresholds
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Prioritizes reliability, high recovery rate (75,100 BTU), and simple venting over maximum efficiency
Full spec sheet available at StateWaterHeaters.com.
🌪️ How Venting Type Affects UEF
🏋️ Atmospheric Vent
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Typical UEF: 0.58-0.62
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More standby losses from open flue
🏙️ Power Vent
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Typical UEF: 0.65-0.70
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Sealed combustion reduces standby losses
🌍 Condensing Models
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Typical UEF: 0.85-0.95
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Capture heat from exhaust gases
🔦 How to Use UEF When Shopping for a Water Heater
🔍 Prioritize Based on:
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Household size and peak hot water demand
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Available venting infrastructure
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Budget for upfront costs vs. long-term savings
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Available rebates and tax incentives
🌟 Don't Ignore Reliability
Sometimes a modestly efficient model with proven reliability (like atmospheric vent models) offers better overall value for specific homeowners.
🏛️ Upcoming Efficiency Standards for 2025 & Beyond
🧰 DOE Proposals
The DOE has proposed stricter minimum UEF standards for residential gas water heaters by 2029, including:
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Condensing technology likely becoming mandatory for tanks over 55 gallons
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Higher UEF baselines across all categories
Stay informed at the DOE Appliance Standards Program.
🧮 Impact on Atmospheric Vent Models
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May face gradual phase-outs in favor of sealed systems
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Retrofitting existing chimneys will remain possible but less common in new builds
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Ongoing grandfathering for replacement installations likely
🔧 Alternatives for Higher Efficiency Seekers
🌱 Condensing Tank Models
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High upfront cost
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Significant energy savings long-term
🤫 Tankless Gas Water Heaters
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Virtually unlimited hot water
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Very high UEF ratings
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Complex installation
🚒 Hybrid Systems
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Combine solar or heat pump technologies
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Maximize available tax credits
Review upgrade paths via Consumer Reports.
🫶 Samantha Reyes' Quick Buyer Checklist for Gas Water Heater Efficiency 📝
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☑ Verify UEF rating based on your household size profile
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☑ Compare first-hour ratings alongside efficiency
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☑ Check venting type compatibility
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☑ Balance long-term savings against upfront costs
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☑ Explore utility and tax incentives
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☑ Prioritize reliable, trusted brands for peace of mind
🛡️ Conclusion: Understanding UEF Empowers Better Decisions
The switch from EF to UEF makes shopping for water heaters far more intuitive. While the State ProLine 74-Gallon Atmospheric Vent model may not top the UEF charts, its robust recovery, reliability, and suitability for certain venting scenarios still make it a very smart choice for large households.
Efficiency should never come at the cost of reliability, safety, or suitability for your home's infrastructure. With the knowledge of how UEF works, you can confidently evaluate all your options.
Authored for The Furnace Outlet by Samantha Reyes, Home Energy Specialist.
In the next topic we will read about: State ProLine vs. AO Smith vs. Bradford White, Which Gas Water Heater Is Best for Large Homes?
