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2 Bedrooms 1 Bathrooms Peak Flow: 4.5 GPM (17 L/min) 2 - 3 People

Tankless Water Heater Sizing for 2 Bedroom, 1 Bathroom Home

A standard 2 bedroom, 1 bathroom home requires a peak hot water capacity of 4.5 GPM to support 1 simultaneous shower plus concurrent kitchen or laundry fixtures. Compare with our Tankless Sizing Chart and master Water Heater Sizing Calculator.

1. Groundwater & Target Temperatures ΔT = Target − Incoming
Incoming:
°F
°F (120°F Code Standard)
2. Peak Hot Water Fixture Demand Select fixtures operating concurrently during morning rush
Active Fixture Type Qty Flow (GPM)
Standard Shower (2.0 GPM)
Bathroom Sink Faucet (1.0 GPM)
Kitchen Sink Faucet (1.5 GPM)
Bathtub Filler (4.0 GPM)
Dishwasher (1.5 GPM)
Clothes Washer (2.0 GPM)
Required Peak Tankless Flow Rate
6.0 GPM at 70°F Rise
Metric Equivalent: 22.7 L/min at 38.9°C Rise
Required Heating Power 210,000 BTU/hr 61.5 kW Power
Groundwater Temperature Rise 70°F 50°F in → 120°F out
Estimated Electrical Draw 256 Amps 240V Dedicated Electrical Service
Total Connected Fixture Capacity 15.0 GPM If all home fixtures opened simultaneously

Your peak simultaneous hot-water demand is 6.0 GPM (22.7 L/min) with a 70°F (38.9°C) temperature rise (incoming 50°F → desired 120°F). To deliver this flow reliably, your Gas tankless heater must produce approximately 210,000 BTU/hr (61.5 kW). Ensure the chosen model provides at least 6.0 GPM at a 70°F rise.

Dynamic Flow vs. Temperature Rise Matrix Required BTU/hr (kW)
Temperature Rise (ΔT) 2.0 GPM 3.0 GPM 4.0 GPM 5.0 GPM 6.0 GPM
40°F Rise 40k BTU (11.7 kW) 60k BTU (17.6 kW) 80k BTU (23.4 kW) 100k BTU (29.3 kW) 120k BTU (35.2 kW)
50°F Rise 50k BTU (14.7 kW) 75k BTU (22 kW) 100k BTU (29.3 kW) 125k BTU (36.6 kW) 150k BTU (44 kW)
60°F Rise 60k BTU (17.6 kW) 90k BTU (26.4 kW) 120k BTU (35.2 kW) 150k BTU (44 kW) 180k BTU (52.8 kW)
70°F Rise 70k BTU (20.5 kW) 105k BTU (30.8 kW) 140k BTU (41 kW) 175k BTU (51.3 kW) 210k BTU (61.5 kW)
80°F Rise 80k BTU (23.4 kW) 120k BTU (35.2 kW) 160k BTU (46.9 kW) 200k BTU (58.6 kW) 240k BTU (70.3 kW)
Highlighted cell indicates your exact calculated demand requirement.
Recommended Compatible Water Heater Models Matches Your Exact Load
RINNAI

Rinnai RX199iN / RXP199iN

SENSEI® RX Series (Condensing)
5.5 GPM at 70°F Rise (11.1 GPM max)
199,000 BTU/hr 0.98 UEF GAS

Best for large households (3-4 simultaneous showers in cold climates).

RINNAI

Rinnai RX160iN

SENSEI® RX Series (Condensing)
4.4 GPM at 70°F Rise (9 GPM max)
160,000 BTU/hr 0.97 UEF GAS

Ideal for standard 2-3 bathroom homes with moderate to cold groundwater.

RINNAI

Rinnai RX130iN

SENSEI® RX Series (Condensing)
3.6 GPM at 70°F Rise (7 GPM max)
130,000 BTU/hr 0.96 UEF GAS

Ideal for 1-2 bathroom homes or warmer climate zones.

RINNAI

Rinnai V65iN

High Efficiency Plus (Non-Condensing)
3.8 GPM at 70°F Rise (6.5 GPM max)
150,000 BTU/hr 0.82 UEF GAS

Cost-effective non-condensing gas solution for small-to-medium demand.

RHEEM

Rheem RTGH-95DVLN

Performance Platinum® Condensing Gas
5.3 GPM at 70°F Rise (9.5 GPM max)
199,900 BTU/hr 0.93 UEF GAS

High-output gas unit supporting up to 3-4 simultaneous showers.

RHEEM

Rheem RTGH-84DVLN

Performance Platinum® Condensing Gas
4.7 GPM at 70°F Rise (8.4 GPM max)
180,000 BTU/hr 0.93 UEF GAS

Efficient mid-size whole-house gas tankless for 2-3 bathrooms.

RHEEM

Rheem RTEX-27 (240V)

Performance® Electric Tankless
2.6 GPM at 70°F Rise (6.6 GPM max)
27.0 kW (112.5A) 0.99 Energy Factor ELECTRIC

High-power whole-house electric unit (Requires 3x 40A double-pole breakers).

RHEEM

Rheem RTEX-18 (240V)

Performance® Electric Tankless
1.8 GPM at 70°F Rise (4.4 GPM max)
18.0 kW (75A) 0.99 Energy Factor ELECTRIC

Compact electric unit for 1-2 bathroom apartments or warm southern climates.

Climate Zone Sizing Matrix

2 Bed, 1 Bath Water Heater Specs by Region

Required heating capacity changes drastically depending on your local incoming groundwater temperature.

Cold Climate (North / Canada)
Inlet: 40°F Rise (ΔT): 80°F
Required Gas BTU 180,000 BTU/hr
Electric Power 26.4 kW
Recommended Unit Rating 5.5 GPM @ 35°F rise
Moderate Climate (Midwest / Mid-Atlantic)
Inlet: 55°F Rise (ΔT): 65°F
Required Gas BTU 146,000 BTU/hr
Electric Power 21.4 kW
Recommended Unit Rating 4.8 GPM @ 35°F rise
Warm Climate (South / Sunbelt)
Inlet: 70°F Rise (ΔT): 50°F
Required Gas BTU 112,500 BTU/hr
Electric Power 16.5 kW
Recommended Unit Rating 4.5 GPM @ 35°F rise
Fixture Demand Breakdown

Simultaneous Peak Load Calculation for 2 Bed, 1 Bath

How the 4.5 GPM peak simultaneous flow demand is calculated for 2 - 3 People:

  • 1 Main Shower (2.0 GPM)
  • 1 Kitchen Sink (1.5 GPM)
  • 1 Washing Machine (1.0 GPM)
Total Combined Simultaneous Flow: 4.5 Gallons Per Minute (17 L/min)
Natural Gas / Propane
3/4" Natural Gas / Propane Line (160,000 - 180,000 BTU)
Electrical Panel
150-200 Amp panel (Requires 2x or 3x 40A DP breakers for 24-27 kW)
Tank Water Heater Alternative
40 Gallon Storage Tank
Home Size Navigation

Compare Other Home Layout Sizing

Explore water heater sizing calculations for different bedroom and bathroom counts.

← Smaller Home 1 Bed 1 Bath Sizing Overview Guide Complete Water Heater Sizing Chart Larger Home → 2 Bed 2 Bath Sizing
Expert FAQ Guide

2 Bed, 1 Bath Sizing FAQs

Common questions about water heater sizing for 2 bedroom homes.

2 Questions Answered
Q1 What GPM is needed for a 2 bed 1 bath house?

A peak flow rate of 4.0 to 4.5 GPM allows running 1 shower and the dishwasher or washing machine simultaneously without loss of hot water.

Q2 Is electric tankless practical for a 2 bedroom home?

Yes, a 24 kW to 27 kW electric tankless unit (like EcoSmart ECO 27 or Stiebel Eltron Tempra 24 Plus) handles a 2-bedroom home comfortably in most climates provided you have 200A electrical service.

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Quick visual sizing tables matching groundwater temperature zones with GPM fixture loads.

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