About & methodology

tanklesswaterheaterprices.com compares tankless (gas and electric) and heat pump water heaters. It is a sister site of minisplitprices.cc, solarexperts.cc and chlorineprices.com, and works the same way: every price comes from a store's own public product page, every row says when it was last checked, and nothing is ranked by commission.

How tankless heaters are ranked: $/GPM at a 45 °F rise

A tankless heater's output is fixed by its burner or elements; the flow it can deliver depends on how much it has to raise the water's temperature. Makers quote "maximum GPM" at whatever rise they choose, from 25 °F on some portable propane units to 35 °F on most whole-home models. So we work it out ourselves:

• Gas: heat output = maximum input (BTU/h) × UEF. Where the UEF isn't published we assume 0.93 for condensing and 0.82 for non-condensing units, and say so on the product page.
• Electric: heat output = kW × 3,412 × 0.99.
• GPM at a rise = heat output ÷ (500 × rise in °F), capped at the maker's maximum flow. (500 = 8.34 lb per gallon × 60 minutes.)

Tables rank on price ÷ GPM at a 45 °F rise, which is typical across much of the US for a 120 °F setpoint with mains water in the 70s, or for a 105 °F shower drawn from 60 °F water. The maker's own figure is shown alongside as "Box GPM".

How heat pump water heaters are ranked: $/gallon

Heat pump water heaters are tanks, so tables rank on price per gallon of capacity. The first-hour rating (FHR), which says how much hot water the tank delivers in a busy hour, and the UEF, which sets the running cost, sit in their own columns, and the sizing calculator weighs both.

The sizing calculator

• Inlet water temperature comes from your ZIP code's climate zone using the NREL (Burch & Christensen) mains model that DOE's BEopt uses: annual average air temperature + 6 °F, swinging with the seasons. You can type your own.
• Tankless: the heat needed at the busiest moment, adding up each shower and tap at its own use temperature (105 °F showers, 110 °F kitchen tap), so mixing at the tap is counted exactly.
• Tank: the busiest hour in gallons of setpoint water (showers × flow × minutes, plus 2 gallons a person for washing and shaving, 5 for food prep, and 6 for a dishwasher and 7 for a clothes washer if they run then, as in the DOE sizing worksheet), against each tank's first-hour rating.
• Running cost: daily gallons (about 12 + 13 per person, matching DOE's draw patterns) × 8.34 × (setpoint − average inlet) ÷ UEF.

It is a rule-of-thumb estimate. A plumber should confirm gas line sizing, venting and electrical capacity.

Where the prices come from

• Store prices are read from each store's own product page (Shopify product data or the page's schema.org markup) by a daily job. If a page can't be read, the price is left alone and its "checked" badge ages from green to amber (over 7 days) to red (over 30), which is the honest signal.
• A listing we have found but not yet priced shows "pending" and links to the store.
• Amazon prices are fetched live through Amazon's API when a page loads and are never stored, as Amazon's terms require. Until that API is connected, Amazon rows show a "Check price" link.
• Marketplace listings (AliExpress, eBay) are labelled with the store; check the seller and shipping time before buying.
• Specifications come from the manufacturer's spec sheet or product page; the source is linked on each product page. A figure the maker doesn't publish is shown as "--", never guessed.

Incentives

The federal 25C tax credit for heat pump water heaters and efficient gas water heaters ended for equipment installed after December 31, 2025. Many utilities and states still offer rebates on ENERGY STAR heat pump water heaters, some of them instant at the register. Check your utility before buying.

Affiliate links

Some outbound links earn us a commission if you buy, at no cost to you. Stores without an affiliate program are listed exactly the same way, and the ranking never looks at commissions.