Appliances / Heat pump water heaters / Carnot Labs, Inc.
Carnot Labs, Inc. N51
47 gal · 240-volt integrated heat pump water heater
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- Price. Check what it costs at the store.
- Plus running cost. Add $3,320 of electricity over 13 years. That is the part the price tag hides.
- Compare. Pick your state below, then check the cheaper-to-run models of the same size.
About the Carnot Labs, Inc. N51
The Carnot Labs, Inc. N51 is a 47 gal 240-volt integrated heat pump water heater certified by ENERGY STAR. Its official test figure is 1,404 kWh of electricity a year, which at the U.S. average price of 18.19¢ per kWh comes to $255 a year, or $3,320 over a typical 13-year life.
For the same hot water, a standard electric tank water heater would use about 5,387 kWh a year, so this model uses 74% less electricity and saves about $725 a year.
Among 371 240-volt integrated models it ranks #362 for running cost. The cheapest model of this type would save $1,800 in electricity over 13 years, though it may differ in size and features.
If you want the same type and a similar size for less to run, the GE Profile PH40S10BPY01 uses 773 kWh a year and would save about $1,492 over 13 years.
Cost to run where you live
1,404 kWh a year (ENERGY STAR test figure) × 18.19¢ per kWh, the average residential price in the U.S. for Jan–Aug 2026 (EIA). Your bill depends on your utility and how you use it.
Cheaper to run, same type and size
Or see every under 50 gallons model ranked.
| GE Profile PH40S10BPY01 | 40 gal | $141/yr | saves $1,492 |
| A. O. Smith HPS10-50H45DV 2 series | 46 gal | $151/yr | saves $1,355 |
| A. O. Smith HPSN10-50H45DV 2 series | 46 gal | $151/yr | saves $1,355 |
| A. O. Smith HPTS-50 2 series | 46 gal | $151/yr | saves $1,355 |
Specs
| Brand | Carnot Labs, Inc. |
| Model | N51 |
| Type | 240-volt integrated |
| Energy use | 1404 kWh / year |
| Federal maximum for this type | 5387 kWh / year |
| Size | 47 gal |
| Width | 18.9 in |
| Tank size | 47 gal |
| First-hour rating | 75 gal |
| Efficiency (UEF) | 3.53 |
| Usage pattern | High-Usage |
| Voltage | 240 |
| Tank height | 44.2 in |
| Tank diameter | 18.9 in |
Specs and energy use from the ENERGY STAR certified products list (U.S. EPA). An asterisk in a model number stands for colour or finish codes. HouseholdLeak is not affiliated with ENERGY STAR or the EPA.
Questions people ask
How much does the Carnot Labs, Inc. N51 cost to run?
About $255 a year at the U.S. average electricity price (18.19¢/kWh), based on its ENERGY STAR rating of 1,404 kWh a year. In a state with expensive power it can be much more; pick your state on this page to see your number.
How much will the Carnot Labs, Inc. N51 cost in electricity over its life?
About $3,320 over 13 years, a typical life for a heat pump water heater. Add that to the price you pay to get the true cost to own.
Is the Carnot Labs, Inc. N51 energy efficient?
Yes. It is ENERGY STAR certified and uses 74% less electricity than a standard electric tank water heater.
Is there a cheaper water heater to run of the same type and size?
Yes. The GE Profile PH40S10BPY01 uses 773 kWh a year, about $1,492 less in electricity over 13 years.
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