WattCost

Data through April 2026

Running cost · Water Heaters (Electric) · ENERGY STAR certified

Rheem PROPH40 T0 RH120-MSO

For a standard household draw pattern, the Rheem PROPH40 T0 RH120-MSO uses a certified 780 kWh per year: roughly $147 annually at the national average rate. That puts it in the most efficient tenth of every certified electric water heater — 28% less electricity than the median, ranked 17 of 566. Where you live moves the bill from $96 a year in North Dakota to $364 in Hawaii.

Estimated annual running cost · U.S. average rate 18.8¢/kWh

$147/yr

$121 · cheapest certified water heaters (electric)$328 · priciest
Per month
$12.24
Per day
40¢
Certified use
780 kWh/yr
Type
Hybrid/Electric Heat Pump
Heat pump type
120 Volt Integrated HPWH
Storage volume
36 gal
First-hour rating
45 gal
UEF
2.8
643 kWh1,741 kWh
Where the Rheem PROPH40 T0 RH120-MSO (▮) sits among all 566 certified water heaters (electric), by annual kWh

What it costs in every state

Rheem PROPH40 T0 RH120-MSO: 780 kWh/yr × each state's average residential rate (EIA)
StateRate ¢/kWhThis model $/yrRelative cost
Alabama17.4¢$136
Alaska27.4¢$213
Arizona15.5¢$121
Arkansas14.2¢$110
California35.3¢$275
Colorado16.5¢$129
Connecticut32.2¢$251
Delaware18.8¢$147
District of Columbia25.4¢$198
Florida15.4¢$120
Georgia15.4¢$120
Hawaiipriciest46.6¢$364
Idaho12.7¢$99
Illinois20.5¢$160
Indiana17.9¢$140
Iowa13.9¢$108
Kansas15.8¢$123
Kentucky15.0¢$117
Louisiana14.4¢$113
Maine28.4¢$222
Maryland22.1¢$172
Massachusetts29.4¢$230
Michigan21.4¢$167
Minnesota16.4¢$128
Mississippi16.8¢$131
Missouri14.0¢$109
Montana13.9¢$108
Nebraska13.3¢$104
Nevada14.3¢$111
New Hampshire27.2¢$212
New Jersey23.5¢$184
New Mexico15.2¢$118
New York29.4¢$230
North Carolina16.3¢$127
North Dakotacheapest12.3¢$96
Ohio19.5¢$152
Oklahoma13.3¢$104
Oregon15.8¢$123
Pennsylvania21.5¢$167
Rhode Island28.3¢$221
South Carolina17.1¢$133
South Dakota14.5¢$113
Tennessee14.9¢$117
Texas17.0¢$133
Utah13.3¢$104
Vermont24.6¢$192
Virginia17.4¢$136
Washington14.4¢$112
West Virginia16.1¢$125
Wisconsin19.2¢$150
Wyoming14.7¢$115

Certified models closest in efficiency

electric water heaters within reach of 780 kWh/yr
ModelkWh/yr$/yr (US avg)
Friedrich PROH40 T0 FD120-M780$147
Friedrich PROH40 T0 FD120-MSO780$147
Rheem PROPH40 T0 RH120-M780$147
Rheem XE40T10HM00U0780$147
Rheem XE40T10HMS00U0780$147
Richmond 10E40-HP120M780$147

Run your own numbers

Your rate, your numbers

Per day
40¢
Per month
$12.24
Per year
$147

780 kWh/yr × 18.8¢/kWh = $147/yr

Prefilled with this model's certified 780 kWh/yr — adjust if your usage differs from the DOE test basis. The certified annual kWh comes from the DOE Uniform Energy Factor test, which simulates a typical household's daily hot-water draw pattern. Only electric models (including heat-pump units) are listed — gas models burn gas, not kWh.

Questions, answered with the data

How much electricity does the Rheem PROPH40 T0 RH120-MSO use?
ENERGY STAR certifies the Rheem PROPH40 T0 RH120-MSO at 780 kWh per year. The certified annual kWh comes from the DOE Uniform Energy Factor test, which simulates a typical household's daily hot-water draw pattern. Only electric models (including heat-pump units) are listed — gas models burn gas, not kWh.
How much does the Rheem PROPH40 T0 RH120-MSO cost to run per month?
About $12.24 a month at the U.S. average residential rate (18.8¢/kWh) — 40¢ a day, or $147 a year. Your state's rate moves this up or down; see the table above.
Is the Rheem PROPH40 T0 RH120-MSO energy efficient?
It uses 28% less electricity than the median certified electric water heater, placing it in the top 10% of certified models.
What does the Rheem PROPH40 T0 RH120-MSO cost to run in the cheapest vs. priciest state?
At current residential rates it costs about $96 a year in North Dakota (12.3¢/kWh) and $364 in Hawaii (46.6¢/kWh).

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