How much does a tankless water heater actually cost?
A whole-home tankless (on-demand) gas water heater typically runs $1,000–$3,500 for the unit itself plus $1,500–$3,500 for professional installation, depending on vent routing, gas-line sizing, and whether you are retrofitting away from a storage tank. That puts a turnkey replacement in the $2,800–$7,000 range for most homes. By contrast, a storage-tank replacement lands closer to $1,400–$2,200 installed.
The premium on tankless is real, but the Department of Energy puts the energy savings at roughly 27% on water-heating gas usage, and a tankless unit typically outlasts two storage tanks — so the lifetime numbers come out ahead. Your exact payback depends on your local gas rates, household size, and how much of a recirc loop your home has.
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Open the Savings Estimator →Do tankless water heaters need special venting?
Yes, but in most retrofits it's a smaller job than homeowners expect. Modern high-efficiency (condensing) tankless units direct-vent through a single concentric PVC pipe — intake and exhaust in the same line — and can typically terminate through an exterior wall rather than up through the chimney. That eliminates the masonry chimney requirement that older natural-draft tank units had.
Non-condensing units still need Category III stainless venting, which a licensed plumber can usually route through an existing penetration. The short version: tankless venting is well-understood, code-compliant, and rarely the reason an installation has to be torn back open.
Will a tankless water heater work in cold climates or with low inlet-water temperatures?
Yes, but sizing matters more than in a mild climate. Inlet-water temperature in winter is the limiting factor: a unit rated at 7 GPM in 60 °F inlet water may only deliver 4.5 GPM at 35 °F inlet water. For most households in the Northeast and Midwest this still works, but you want a cold-climate-rated model with a built-in freeze-protection mode, a wider BTU modulating range, and dedicated condensate management.
Condensing units handle the byproduct condensate by routing it to a drain — non-condensing units in very cold installs may need a vent-side neutralizer. A licensed installer will measure your incoming winter water temperature and pick the right model; this is one of the most common things an inexperienced installer gets wrong on a northern install.
How much yearly maintenance does a tankless water heater need?
Plan on about 15–30 minutes per year, not hours. The annual service is a descaling flush: a service tech shuts off the cold-water and gas valves, connects a submersible pump and a 5-gallon bucket of food-grade white vinegar (or citric-acid solution), circulates it through the heat exchanger for 45–60 minutes, then flushes with clean water.
If your home has hard water (over 7 grains per gallon), you should also install a small inline scale-preventer or plan a flush every 9 months instead of every 12. The inlet air filter — usually a small mesh screen behind the front cover — should be cleaned out every 6 months with a quick vacuum or soft brush. Most manufacturers require the annual flush to keep the heat-exchanger warranty in force; skipping it is the #1 reason tankless warranties are denied.
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Find Local Tankless Pros →How long does a tankless water heater last?
A gas tankless unit professionally installed and annually descaled has an expected service life of 20+ years — roughly double the 10–12-year lifespan of a storage-tank water heater. The main wear item is the heat exchanger, and on higher-end units that's a replaceable sub-assembly rather than a scrap-the-whole-unit failure mode: a rebuilt heat exchanger runs $300–$600 in parts with a few hours of labour, instead of a full $2,800–$7,000 tankless replacement.
The control board and igniter are also field-replaceable. The "20+ years" figure assumes the annual descaling — without it, premature scale buildup on the heat exchanger is the most common failure cause. That's why the maintenance hire matters as much as the install hire.
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Do tankless water heaters work during a power outage?
A gas or electric tankless water heater needs electricity to run the control board, the flow sensor, and the igniter — without power, no hot water, even if the gas is still on. A traditional storage tank keeps a 40-gallon reservoir warm for 2–4 hours after a power loss, then cools; pilot-light models keep working indefinitely as long as the gas stays on.
A small UPS (1,000 VA, $150–$300) on the tankless circuit keeps one or two showers available during short blips but won't carry you through a multi-day Piedmont winter storm. For most Union County households the trade-off is acceptable — but it is worth understanding before you swap the tank out.