Tech Bulletin
1 TB-150
10/2018
Technical Bulletin 150 - Understanding EF and UEF
The Department of Energy (DOE) is responsible for
dening and implemenng energy conservaon
standards and tesng procedures for various equipment
and appliances, including water heaters.
On June 12, 2017, the DOE introduced a new metric for
communicang the energy eciency of residenal water
heaters called the Uniform Energy Factor (UEF), replacing
the previous Energy Factor (EF). All manufacturers were
required to report and list their UEF numbers as of this
date.
UEF applies only to residenal water heaters.
Commercial water heaters connue to be rated on
Thermal Eciency.
Why are the Rangs Dierent?
While both EF and UEF measure the energy eciency of
the water heater, it is the tesng procedures that are
dierent. The main dierence is that the new test
procedure for UEF is intended to:
• Beer represent how people use hot water today
• Make it easier to compare one water heater to
another
• Simplify the selecon process for consumers
How is the UEF Rang Calculated?
UEF rangs are determined by assigning water heaters
into one of four categories of hot water based on their
usage and then evaluang their performance based on
that usage. Each category has a specic hot water draw
paern and a water heater is assigned a category based
the hot water delivery capacity. A greater UEF rang will
indicate that the water heater in that category is more
ecient.
All Energy Guide labels now include updated
performance informaon to help consumers and
contractors choose the water heater that best
accommodates their needs. It is important that
consumers and contractors understand that the change
to UEF rangs is only a change to the way water heaters
are being tested, measured, and communicated. Rinnai
Tankless Water Heaters remain as ecient as they
always have been and are built with the same quality
that our brand is known for.
Rinnai UEF Rangs
Although the DOE minimum eciency level has
changed from 0.82 EF to 0.81 UEF for water heaters,
this only applies to tankless water heaters
manufactured aer June 12, 2017; thus, water heater
models manufactured prior to June 12, 2017 are not
subject to the 0.81 minimum eciency requirement.
Therefore, you can be assured that all Rinnai Tankless
Water Heaters meet the required eciency standards
according to DOE regulaons and can be sold both in
the US and Canada.
The table below reects the transion from EF to UEF
for Rinnai Tankless Water Heaters.