Tankless water heater sizing Last reviewed June 30, 2026
What Size Tankless Water Heater for a Family of 2—?
By the WhatSize editorial team 4 min read Standards-reviewed
A family of 2–3 needs 5–7 GPM gas (130–180k BTU) or 3–4 GPM electric (18–24 kW). Budget pick: Camplux CA318 at 3.18 GPM / 82k BTU / $399.
Why 2— person households have flexible tankless options
A 2–3 person household has lower peak demand (typically 1–2 showers + 1 kitchen = 4–5 GPM per ENERGY STAR fixture rates: shower 2.5 GPM ×1 = 2.5, kitchen 2.2, bath 1.0, DW 1.3 = 7 GPM peak if everything runs at once; or 4 GPM with normal staggered use).
Gas sizing: BTU = GPM ×500 ×ΔT = 4 ×500 ×65 = 130,000 BTU. Standard 130k BTU gas tankless covers this. Top picks per ENERGY STAR: Bradford White RTGR150N1 (150k BTU, 4.3 GPM, UEF 0.98, NG); Noritz EZ71DV (160k BTU, 4.7 GPM, UEF 0.98, NG/LP dual-fuel).
Electric sizing: kW = (4 ×8.33 ×65) × 3412 = 6.3 kW. Standard 11 kW or 13.5 kW electric tankless. Top picks: Camplux TEW11 (11 kW, $239), TEW14 (14 kW, $287).
Point-of-use vs whole-house: For 1-bathroom homes with low usage, point-of-use electric ($200–$500 per unit) under each fixture is budget-friendly. For 2+ bathrooms, whole-house tankless is more practical.
Top picks for this size
These Amazon-available picks meet the calculated spec. For region-specific or licensed contractor-installed options, consult a local professional. See our Disclaimers.
When to choose whole-house vs point-of-use
- 1-bathroom 2-person home: Point-of-use electric $200–$500 or 130k BTU gas (Bradford White RTGR130 series).
- 2-bathroom 3-person home: Whole-house 130–150k BTU gas (Bradford White RTGR150N1, Noritz EZ71DV).
- 2-person, low usage: Small electric 11–18 kW (Camplux TEW11, TEW14) handles 1 shower + kitchen.
- 3-person, frequent simultaneous use: 150k BTU gas (Noritz EZ71DV) or 18 kW electric (EcoSmart ECO 18).
Frequently asked questions
What size tankless for 2 people?
Two people with one bathroom typically need 3–5 GPM (small electric or 130k BTU gas). Two people with two bathrooms need 5–7 GPM (180k BTU gas or 18–24 kW electric). For 3-person households, plan for 4–7 GPM gas or 24 kW electric.
Is point-of-use tankless worth it for 2— people?
Yes, for 1-bathroom homes with low usage. A point-of-use electric ($200–$500) under the kitchen sink and another under the bathroom sink handles single-fixture demand efficiently. For 2+ bathrooms, whole-house tankless is more practical. Example: <a href="https://camplux.com/collections/tankless-water-heater" class="text-brand-800 hover-underline">Camplux CA318</a> at 3.18 GPM / 82k BTU / $399 covers 1–2 person point-of-use well.
What's the cheapest tankless water heater?
Small electric point-of-use units start at $150–$300 (EcoSmart ECO 11, Bosch Tronic 3000). These deliver 2–3 GPM at high ΔT — enough for a single bathroom sink or kitchen sink, but not a shower. <a href="https://camplux.com/collections/tankless-water-heater" class="text-brand-800 hover-underline">Camplux</a> has the lowest entry at ~$227 for the TEW08 8 kW electric.
How many GPM for a small family?
A 2-person family with one bathroom needs 3–5 GPM. A 3-person family with one bathroom needs 4–6 GPM. A 3-person family with two bathrooms needs 5–7 GPM. Add 1 GPM safety buffer in all cases.
You might also need
More tankless water heater sizing guides
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- Gas Tankless Water Heater Sizing Guide
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- Tankless Water Heater Sizing for Cold Climates
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- Tankless Water Heater Installation Cost Guide
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