Electric Tankless Water Heater Size Calculator

Results

Required Heater Specifications:

  • Required Power: 0 kW
  • Temperature Rise: 0 °F
  • Maximum Flow Rate: 0 GPM
  • Minimum Circuit Breaker: 0 Amps

Tankless Water Heater Basics

Understanding the key factors in sizing an electric tankless water heater.

  • Temperature Rise The difference between inlet and desired output temperature.
  • Flow Rate (GPM) The gallons per minute of hot water needed.
  • Power Requirements The kilowatts needed to heat water to desired temperature.
  • Electrical Requirements Voltage and amperage needs for proper installation.

Heating System Design

  • Power Requirements Heating capacity: 1.5-5.5 kW/GPM. Voltage range: 208-240V. Current draw: 25-200A. Power factor: 0.98-0.99. Efficiency: 98-99%.
  • Flow Characteristics Activation flow: 0.3-0.5 GPM. Maximum flow: 8-12 GPM. Pressure drop: 0.5-3.0 psi. Recovery rate: 2-4 GPM/min. Response time: 1-3 seconds.
  • Temperature Control Range: 80-140°F. Accuracy: ±1-2°F. Modulation steps: 20-40. Stabilization time: 2-5s. Maximum rise: 70-90°F.

Performance Standards

  • Operating Parameters Working pressure: 15-150 psi. Temperature limit: 160°F. Standby power: <1W. Duty cycle: continuous. Life expectancy: 15-20 years.
  • Safety Features Over-temperature: 165°F cutoff. Dry fire protection: flow sensor. Ground fault: 5mA GFCI. Pressure relief: 150 psi. Thermal fuse: 185°F.
  • Energy Efficiency Standby loss: 0%. First hour rating: 100%. Energy factor: 0.98-0.99. UEF rating: 0.96-0.98. Thermal efficiency: >98%.

Installation Requirements

  • Electrical Service Circuit breaker: 2-4 poles. Wire gauge: 6-2 AWG. Ground resistance: <0.1Ω. Disconnect rating: 125-200%. Conduit size: 3/4-1.5".
  • Plumbing Integration Pipe size: 1/2-3/4". Connection type: NPT/BSPP. Isolation valves: full port. Expansion tank: 2-4 gal. Service clearance: 12-24".
  • Ventilation Needs Ambient temperature: 40-120°F. Air circulation: natural. Humidity range: 5-95%. IP rating: 24-54. Condensation protection: required.

Maintenance Protocol

  • Regular Service Inlet filter: 6 months. Element inspection: annual. Scale removal: 1-2 years. Flow sensor: annual. Control calibration: 2 years.
  • Performance Testing Temperature accuracy: monthly. Flow rate verification: quarterly. Power consumption: semi-annual. Safety devices: annual. Pressure test: 2 years.
  • Water Quality Hardness limit: <180 ppm. TDS range: <500 ppm. pH level: 6.5-8.5. Chloride content: <250 ppm. Conductivity: <800 μS/cm.

Sizing Guidelines

Climate Considerations

Colder climates require more powerful units.

Usage Patterns

Consider peak demand times.

Installation Location

Affects inlet water temperature.

Maintenance

Regular descaling for optimal performance.