热水器能效计算器 — 公式

How to Calculate Water Heater Costs

Water heating is typically the second largest energy expense in a home (14-18% of energy bills).

Formula

Daily BTU = Gallons * Temp Rise * 8.33

Annual Energy = Daily BTU * 365 / Energy Factor

Energy Factors

  • Standard gas: 0.60-0.70
  • High-efficiency gas: 0.80-0.98
  • Electric resistance: 0.90-0.95
  • Heat pump water heater: 2.0-4.0

    • 计算示例

    50 gal/day hot water, 60F temp rise, 0.92 energy factor, $0.15/kWh.

    1. Daily BTU: 50 * 60 * 8.33 = 24,990 BTU
    2. Daily energy with EF: 24,990 / 0.92 = 27,163 BTU
    3. Annual energy: 27,163 * 365 = 9,914,526 BTU
    4. Annual cost: 9,914,526 / 3,412 * $0.15 = $436