Plug-in 120-volt vs 240-volt and split heat-pump water heaters: what the ratings show

Among certified heat-pump water heaters, the 120-volt plug-in units have the lowest median UEF and the lowest first-hour output per rated gallon of the three types. At the high draw pattern their median UEF is 3.40, against 3.77 for split systems and 4.00 for 240-volt integrated tanks. This explainer reports what the ratings show; it does not recommend a type.

Three ways to build a heat-pump water heater

The listing sorts heat pumps into three subtypes. Integrated 240-volt units combine compressor and tank in one appliance and are wired to a 240-volt circuit; they make up 441 of the 609 heat-pump model numbers. Integrated 120-volt units plug into a standard outlet (68 model numbers). Split systems put the compressor in a separate unit connected to the tank (100 model numbers).

The ratings side by side

The table keeps each draw pattern in its own column, because a UEF from the medium pattern does not compare with one from the high pattern.

In both patterns the order is the same: 120 V lowest, split systems in the middle, 240 V integrated highest. The same order holds for first-hour output per rated gallon: 1.16, 1.23 and 1.27.

Why the plug-in units rate lower on first hour

The listing gives an input power for most models. The median 120 V model lists 1.0 kW, the median 240 V integrated model 4.5 kW. A tank that reheats with less power recovers less water during the test hour, and the first-hour rating counts that recovery. The plug-in units make up the difference with stored volume rather than reheating speed.

The highest-rated 120 V set on the list is GE Profile PF80S10FPY01, with a UEF of 3.50 at the high pattern. For the full list, see the 120-volt plug-in page.

Split systems and CO2

All 94 of the CO2 (R-744) models on the list are split systems, and no integrated tank uses CO2. That makes the split group the one with the widest spread of results: the group holds the highest first-hour rating among heat pumps and some of the lowest UEFs. The split-system page lists every set.

Connected models

The listing marks whether a model is connected-capable. All the 120 V model numbers are, against 68% of the 240 V integrated and 87% of the split-system model numbers.

Draw patterns by subtype

The subtypes also test at different patterns, which is why the table keeps them apart. Of the 73 integrated 240-volt sets, 45 test at the high pattern and 27 at the medium pattern. The plug-in units split evenly, 5 high and 5 medium, with 2 at the low pattern. The split systems divide 8 high, 6 medium and 2 low. A single median across all patterns would mix these test days, so the site never reports one, and each subtype page groups its table by pattern for the same reason.

Sizes and electrical listing

The three groups overlap in size. Rated volumes run from 36 gal to 82 gal for the plug-in units, 36 gal to 119 gal for the 240-volt tanks and 43 gal to 120 gal for split systems. The listing also gives a maximum current: the median plug-in model lists 12 A, the median 240-volt integrated model 22 A and the median split system 20.2 A.

Who lists them

Two partners dominate the integrated tanks. Rheem Sales Company, Inc. lists 169 of the 441 240-volt integrated model numbers and 46 of the 68 plug-in model numbers. The split systems are concentrated in another listing: A.O. Smith Corporation accounts for 84 of 100.

Sound, where listed

Some listings report a sound level in dBA. Where they do, the median is 49 dBA for 240-volt integrated models (108 listed), 45 dBA for plug-in models (22 listed) and 37 dBA for split systems (13 listed). So few models report a value that the gaps are a rough guide only.

Reading the comparison

These are medians of certified test results. Inside each subtype the range is wide, and individual sets overlap: some split systems out-rate many 240-volt tanks, and the highest-rated plug-in units sit above the weakest 240-volt tanks. The Heater finder lets you filter by subtype and compare sets directly.