MCPCalc

Water Heater Calculator

Calculate water heater size based on household usage.

Scratchpad (not saved)

people

What This Calculator Does

Calculate water heater size based on household usage.

It combines Number of People, Number of Bathrooms, Dishwasher, Laundry to estimate Recommended Size, Peak Hour Demand, First Hour Rating.

Formula & Method

Peak hot-water demand is estimated by fixture/event loads: D_{peak}=20\cdot Showers+14\cdot Dishwasher+0.5\cdot32\cdot Laundry (gallons). Tankless sizing converts demand to flow target (GPM), while tank sizing maps peak demand to standard tank capacities.

Notation used in the formulas: R = Recommended Size; x_{1} = Number of People; x_{2} = Number of Bathrooms; x_{3} = Dishwasher; x_{4} = Laundry; x_{5} = Heater Type.

Method summary: inputs are normalized to consistent units, core equations are evaluated, then secondary values are derived and rounded for display.

Use this calculator for quick scenario analysis. Start with baseline values, change one driver at a time, and compare how sensitive the results are to each input shown above.

Inputs Used

  • Number of People: Used directly in the calculation.
  • Number of Bathrooms: Used directly in the calculation.
  • Dishwasher: Used directly in the calculation.
  • Laundry: Used directly in the calculation.
  • Heater Type: Used directly in the calculation.

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