WattMath

Water Heater Comparison Calculator

Compare operating costs and efficiency between electric tank, gas tank, tankless, and heat pump water heaters to find the best option for your household.

Your Hot Water Usage

Number of people

~20 gal/person typical

Cold water from pipes

120°F recommended

Energy Rates

US average: $0.12/kWh

US average: $1.20/therm

Water Heater Types

Water heating accounts for 14-18% of home energy use. Choosing the right type can save hundreds annually.

  • Tank: Stores hot water, lower upfront cost
  • Tankless: On-demand heating, more efficient
  • Heat Pump: 2-3x more efficient, higher upfront

How to Use

  1. Enter your household size and daily hot water usage
  2. Set your local electricity and gas rates
  3. Optionally include installation costs for full comparison
  4. Click Compare to see costs for all water heater types

FAQ

Which water heater is most efficient?

Heat pump water heaters are the most efficient, operating at 200-300% efficiency by extracting heat from air. They use 2-3x less energy than standard electric tanks, though they cost more upfront.

Is gas or electric cheaper?

It depends on local rates. Gas is often cheaper per BTU but less efficient. Electric tanks are simple and cheap to install. Heat pump water heaters can make electric cheaper than gas in most areas.

How long do water heaters last?

Tank water heaters typically last 10-15 years. Tankless units can last 20+ years with proper maintenance. Heat pump water heaters average 12-15 years. Lifespan varies with water quality and usage.