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Point-of-Use Tankless Heaters
Quick answer: A point-of-use tankless is a small unit at or near one fixture (sink or single bath), typically delivering about 0.5–2.5 GPM. Most are electric (3.5–18 kW) and cost roughly $150–$600 plus install. Example: a 6 kW unit heats about 1.0 GPM by 40°F — enough for a hand sink.
Context: heat right where you use it
Whole-home units serve every tap from one location. Point-of-use (POU) units sit under a sink, in a cabinet or on a wall beside a single fixture. They cut the wait for hot water, reduce heat lost in long pipe runs and can serve additions, garages, offices or distant bathrooms without re-plumbing the whole house.
Terms
- Mini / under-sink unit: 2.5–7 kW, usually for one faucet.
- Single-bathroom unit: 9–18 kW, for a shower plus sink in warm climates.
- Booster: a POU unit that tops up lukewarm water from a distant main heater.
- Thermostatic vs non-thermostatic: thermostatic units modulate to hold a set temperature.
Sizing table (example)
| Use | Example flow | Rise | Example kW |
|---|---|---|---|
| Hand sink | 0.5–1.0 GPM | 40°F | 3–6 kW |
| Kitchen sink | 1.0–1.5 GPM | 50°F | 7–11 kW |
| Shower, warm climate | 2.0 GPM | 45°F | 13–14 kW |
| Shower, cold climate | 2.0 GPM | 70°F | 20–21 kW |
Formula: kW ≈ GPM × rise ÷ 6.83. Check amps in the electric amps calculator.
Process: deciding on point-of-use
- Identify the fixture and its flow rate.
2. Find your rise — at a far tap, inlet may be cold supply or lukewarm from the main heater.
3. Calculate kW and amps.
4. Confirm a suitable dedicated circuit is available with a licensed electrician.
5. Check space, mounting and access for maintenance.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: basement bathroom 70 feet of pipe from the main tank; users wait about 60 seconds for hot water at the sink.
- POU at the sink: 1.0 GPM, 45°F rise → about 6.6 kW, about 28 A at 240 V.
- Unit: example $250; electrician circuit and install: example $400–$800.
- Water saved: about 1.0 gallon per use × 6 uses a day ≈ 2,190 gallons/yr not run down the drain while waiting.
Total example cost $650–$1,050 for faster hot water and less waste. A recirculation pump on the main system is an alternative worth comparing.
Where POU fits well
- Remote bathrooms, garages, workshops, offices.
- Additions where extending hot-water lines is costly.
- Supplementing a whole-home unit that is near capacity.
Where it struggles
- Full showers in cold climates without a large circuit.
- Homes with no panel capacity for another dedicated circuit.
Mistakes to avoid
- Buying a 3.5 kW mini unit for a shower.
- Ignoring the activation flow on low-flow aerators.
- Installing high-amperage units without a licensed electrician.
FAQ
Can a POU unit plug into an outlet?
Some very small units do; most need a dedicated hard-wired circuit.
Is gas available for POU?
Rarely; POU is overwhelmingly electric.
Does POU need maintenance?
Yes, periodic cleaning of the inlet screen and descaling in hard water.
Can I use POU for the whole home?
Several units can cover a home, but panel capacity often limits it.
Safety and code reminders
Gas, venting, combustion air, condensate disposal and high-amperage electrical work all carry real safety risks, including carbon monoxide, fire, scalding and shock. They are also governed by local code and permits that differ between towns and provinces or states. Treat every step on this page as preparation for a professional visit, not as instructions to do the work yourself. Keep the manufacturer's manual for your exact model, set water temperature with scald risk in mind (120°F is a common household target), and stop and call a licensed professional whenever something is unclear.
Quick reference: typical fixture flow rates
These example flow rates help you translate everyday use into the GPM numbers used throughout this site. Check the rating stamped on your own fixtures, as older fixtures often run higher.
| Fixture | Example hot-water flow |
|---|---|
| Low-flow showerhead | 1.5–1.8 GPM |
| Standard showerhead | 2.0–2.5 GPM |
| Bathroom faucet | 0.5–1.2 GPM |
| Kitchen faucet | 1.0–1.8 GPM |
| Dishwasher | 0.8–1.5 GPM |
| Washing machine (warm) | 1.0–2.0 GPM |
| Bathtub fill | 2.0–4.0 GPM |
Add only the fixtures that genuinely run at the same time. Running the dishwasher or laundry outside shower hours is the simplest way to stay within a unit's capacity.
Questions to ask a licensed installer
Bring these questions to every quote so you can compare them fairly. Good installers welcome them, and the answers often reveal hidden costs before work starts.
- What peak GPM and temperature rise did you size this unit for, and what inlet water temperature did you assume for winter?
- Is my existing gas line, meter or electrical panel large enough, and if not, what exactly needs upgrading and what does that line item cost?
- What venting route will you use, how long is it, and does it meet the manufacturer's instructions and local code?
- Does the quote include a permit, isolation (service) valves for future flushing, a condensate drain if needed, and removal of the old heater?
- What are the labour warranty and the manufacturer's heat-exchanger and parts warranty terms, and do they require registration or yearly professional service?
- How long will the install take, and will there be a period without hot water?
How to read the numbers on this site
Every figure on TanklessMath is a planning estimate. Ranges reflect typical North American examples as of 2026-10-29 and will differ with your region, home, fuel prices and installer. Equipment ratings vary by model, so always check the specification sheet for the exact unit you are considering. When our example and a licensed installer disagree, trust the installer who has seen your home.
Next steps
Write down your peak fixtures, coldest incoming water temperature, fuel type and possible locations, then ask at least two licensed installers to confirm sizing, venting, gas or electrical capacity, permits and local code. Compare written quotes line by line so the unit, labour, materials and upgrades are separated. Questions about this site: hello@charlandandco.com.
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