InstaBidsWhat is a tankless water heater?
A tankless water heater, also called an on-demand or instantaneous water heater, heats household water as needed instead of storing it in a large tank. DOE says high-efficiency gas models often deliver 2–5 gallons per minute. Match capacity to simultaneous fixture use and the required temperature increase when planning installation.
InstaBids is an AI-run marketplace for homeowners and property managers: describe a home job once, by chat or through your own AI assistant, add photos, and get multiple written quotes on the same scope, compared apples to apples, with no phone calls or home visits before you pick.
At a glance
- 2 to 5 gallons per minuteU.S. Department of Energy Building Science Education, read 2026-11-05.
- up to 20 yearsBuilding America Solution Center, Pacific Northwest National Laboratory, read 2026-11-05.
- flow rates below 0.5 gpmBuilding America Solution Center, Pacific Northwest National Laboratory, read 2026-11-05.
What this means for your home project
- List the fixtures and appliances you expect to use together, then give that list to the installer for the peak-demand calculation. Source: Building America Solution Center, Pacific Northwest National Laboratory, read 2026-11-05.
- Request the selected model’s specification sheet and a sizing result that pairs your required flow with its temperature increase. Source: Building America Solution Center, Pacific Northwest National Laboratory, read 2026-11-05.
- Ask for a written venting, gas-line and electrical connection scope that identifies the applicable local codes and manufacturer instructions. Source: Building America Solution Center, Pacific Northwest National Laboratory, read 2026-11-05.
- For a condensing model, request a condensate-disposal line item so the proposal states where that water will go. Source: Building America Solution Center, Pacific Northwest National Laboratory, read 2026-11-05.
- Find the selected model’s installation and owner manuals and use those documents to establish its product-specific maintenance plan. Source: Building America Solution Center, Pacific Northwest National Laboratory, read 2026-11-05.
- Describe it onceBy chat, or through your own AI assistant, and add photos.
- Post it and send itContractors bid in writing on that scope.
- Compare line by lineEvery quote is written against the same scope.
- You chooseContact details stay hidden until you pick and they confirm.
For your AI assistant
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What size tankless water heater do I need?
Use PNNL’s sizing example to match a model’s gallons-per-minute output to the temperature increase your home needs (read 2026-11-05). “Often, high-efficiency endless hot water heaters can provide hot water at a rate of 2 to 5 gallons per minute.” Source: U.S. Department of Energy Building Science Education, read 2026-11-05. “Determine the required temperature rise (based on winter time cold water temperature and desired hot water temperature setpoint).” (source) “For example, in Seattle the average ground water temperature is approximately 52°F.” (source) “Therefore, the temperature rise to reach 120°F is 68°F, so in this example, one would look for a tankless water heater model that can provide at least 4.5 gpm with a temperature rise of 68°F.” (source)
What are the advantages and disadvantages of a tankless water heater?
PNNL’s guidance helps compare tankless operation with a storage tank while accounting for overlapping household hot-water uses (read 2026-11-05). “Because tankless water heaters do not have to keep a large reservoir of water hot, they have almost none of the stand-by losses that tank water heaters have.” (source) “However, there is a limit to the volume of hot water available at any given time.” (source) “For example, if home occupants try to take two showers, start laundry, and wash dishes at the same time, the delivered hot water may not be as hot as desired.” (source)
How long does a tankless water heater last?
PNNL’s comparison, citing IBACOS 2012, gives a planning horizon for discussing tankless replacement alongside a storage heater (read 2026-11-05). “Tankless water heaters are generally considered to last up to 20 years, compared to 10–15 years for tank-type water heaters (IBACOS 2012).” (source)
Why do I have to wait to get hot water after turning on the tap?
PNNL identifies the part of your home’s plumbing to assess when on-demand heating still leaves a wait (read 2026-11-05). “The water distribution system directly affects the delivery time of hot water from a tankless water heater to individual fixtures and appliances.” (source)
Does a tankless water heater work differently with low-flow faucets or showerheads?
Use PNNL’s guidance to find the operating limit to compare with your low-flow fixtures before choosing a model (read 2026-11-05). “When washing hands or washing dishes, often flow rates below 0.5 gpm are desired, but not all tankless water heaters can deliver flow rates this low.” (source) “Minimum flow rates should be listed in the product manufacturer’s literature.” (source)
What drives how much it costs to install a tankless water heater?
Georgia’s consumer guidance identifies possible retrofit work to request as separate items in a tankless installation proposal (read 2026-11-05). “Extra venting hoods for gas models, replacement of existing gas lines with larger ones, additional electrical circuit-breakers, or the need to purchase a second tankless water heater to accommodate simultaneous use of hot water at multiple sites are potential expenses that might not be evident until after installation begins.” (source)
What should I check before I install a tankless water heater?
Use PNNL’s gas-piping reference to frame an installer’s explanation of the sizing method and connection scope (read 2026-11-05). “Tankless Water Heating Gas Piping Facts provides a good explanation along with the pipe diameter formula from the National Fuel Gas Code (NFPA 54, ANSI Z223.1, Section 6.4.1).” (source) “Connect water heater to venting system, gas line, and electricity in a manner compliant with all local codes and manufacturer recommendations.” (source)
Sources
- Water Heaters Gas Fired Tankless — U.S. Department of Energy Building Science Education; read 2026-11-05.
- Gas-Fired Tankless Water Heaters — Building America Solution Center, Pacific Northwest National Laboratory; read 2026-11-05.
- Tankless Water Heaters — Georgia Attorney General’s Consumer Protection Division; published 2020-06-12; read 2026-11-05.