{"id":"water-heater-tankless","version":"0.2.0","classification":{"uniformat":"D2020"},"names":["Water heater, tankless gas"],"aliases":["on-demand water heater","instantaneous water heater","tankless"],"service_life":{"median_years":20,"range_years":[17,20],"range_basis":"source_spread"},"pm_tasks":[],"basis":[{"type":"public_document","life_type":"planning","title":"CNA e-Tool Estimated Useful Life Table","by":"U.S. Department of Housing and Urban Development","url":"https://www.hud.gov/sites/documents/eul_for_cna_e_tool.pdf","page":10,"code":"HUD CNA 3.4.1.2.4","label":"External tankless heater, gas or electric","years":20,"note":"Same life for family and elderly properties. US multifamily housing. HUD's row covers gas and electric tankless heaters."},{"type":"public_document","life_type":"planning","title":"Energy Conservation Program: Energy Conservation Standards for Commercial Water Heating Equipment (final rule), 88 FR 69686, October 6, 2023","by":"U.S. Department of Energy","url":"https://www.govinfo.gov/content/pkg/FR-2023-10-06/pdf/2023-20392.pdf","page":70,"code":"IV.F.6","label":"Table IV.21: \"Gas-fired instantaneous water heaters and hot water supply boilers: Tankless water heaters ... 17\" years","years":17,"note":"Printed page 69755. class: commercial gas-fired tankless (instantaneous) water heaters."},{"type":"public_document","life_type":"planning","title":"Energy Conservation Program: Energy Conservation Standards for Consumer Gas-fired Instantaneous Water Heaters (final rule), 89 FR 105188, December 26, 2024","by":"U.S. Department of Energy","url":"https://www.govinfo.gov/content/pkg/FR-2024-12-26/pdf/2024-30369.pdf","page":43,"code":"IV.F.6","label":"\"DOE estimates the average product lifetime to be around 20 years for instantaneous water heaters\"","years":20,"note":"Printed page 105230. residential: consumer gas-fired instantaneous water heaters (<2 gal, >50,000 Btu/h). Table V.2 (p.75, printed 105262) shows 20.0 years average lifetime at every efficiency level."}],"confidence":{"grade":"B","sample_size":null},"open_questions":["Every source here is a published planning, design or accounting life. None is observed replacement data.","No preventive maintenance tasks are sourced yet."],"contributors":["unfinished.one editors"],"last_reviewed":"2026-10-21","canonical_url":"https://unfinished.one/c/water-heater-tankless","versioned_url":"https://unfinished.one/c/water-heater-tankless/v/0.2.0","licence":"CC-BY-4.0","citation":"unfinished.one (2026). Water heater, tankless gas, v0.2.0. https://unfinished.one/c/water-heater-tankless/v/0.2.0"}