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PerformanceUp to date · Jan 15, 2026

UEF (Uniform Energy Factor)

The standard efficiency metric for water heaters. It measures overall energy efficiency including standby losses. Heat pump water heaters achieve UEF of 2.5-4.0 vs. 0.6-0.7 for gas tank units.

Why It Matters

UEF directly determines your water heating costs. A HPWH with 3.5 UEF uses roughly 5× less energy than a gas tank water heater. Federal standards now require higher minimums.

Related Topics

heat pump water heaters

Related Terms

Heat Pump

An efficient HVAC system that transfers heat rather than generating it, providing both heating and cooling. Air-source heat pumps are most common; ground-source (geothermal) are most efficient.

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