Yearly water-heating cost
Energy use and solar
Worth knowing
UEF measures efficiency
A higher Uniform Energy Factor means the water heater uses less energy to deliver the same hot water. A UEF of 3.5 means about 3.5 units of heat for every unit of electricity.
120V and 240V do different jobs
A 120V model can plug into an existing outlet, often avoiding panel work. A 240V model heats faster after heavy use. Tank size and household demand still matter.
Location matters
Heat pump water heaters pull heat from the air around them and blow out cool, dry air. A garage or roomy utility space usually works better than a small closed closet.
How these numbers are calculated
Daily hot water is estimated at about 10 gallons for the household plus 12 gallons per person, adjusted for light or heavy use. Heating it takes about 559 BTU per gallon, warming 58°F supply water to 125°F, the same conditions used in the federal efficiency test.
Each water heater's energy is that heat divided by its UEF rating. Costs use your gas, propane or electricity rate. Solar size is the added electricity divided by what one kW of solar makes in a year on your roof.
UEF ratings come from a standard lab test. Real results change with the water heater's location, air temperature, tank size and how hot water is used. This leaves out equipment and installation cost, rebates, electrical work, fixed PG&E charges and future rate changes.
About this planning tool
Is this a proposal or quote?
No. This is an educational calculator. It's not a proposal, engineering design, utility bill guarantee or financial promise.
Are the savings guaranteed?
No. Actual costs depend on hot water use, equipment, installation location, PG&E rates and future rate changes.
Why email my results?
It gives you a copy of your inputs and results to review later, share with family, or use to start a more detailed conversation.
What should be checked before installing one?
Electrical panel capacity, a 120V or 240V circuit, the space and airflow around the unit, a condensate drain, and the right tank size for your household.
About NRG Geek
NRG Geek is Robert Kelly's independent educational platform for practical Northern California guidance on solar, battery backup, EV charging, heat pumps and home electrification.
Every home is different. Household size, habits, installation space and electrical capacity all affect the right water heater and real-world costs.
Privacy, legal and terms
How is my information used?
The Email My Results button opens your email app with your inputs and results. Nothing is sent until you send it. If you ask for personal guidance, Robert may follow up. NRG Geek does not sell your personal information.
Is this a proposal or guarantee?
No. Results are estimates for educational planning and are not a proposal, engineering design, financial guarantee or utility bill guarantee.
Third-party links
Linked websites have their own privacy policies and terms. NRG Geek is not responsible for their content.
Accuracy
Equipment ratings, PG&E rates, regulations and incentives change over time. Verify important information before making financial or construction decisions.
Copyright
© 2026 NRG Geek. All rights reserved. This calculator and its educational content may not be reproduced without written permission.