Energy Cost Calculator — Electricity & kWh

Calculate equipment electricity running costs ($/day, $/month, $/year) based on wattage, operating hours, and local utility $/kWh rates.

NEC edition

Inputs

Watts/kW
hrs/day
days/wk

Use 5 for equipment that only runs on weekdays (e.g. an industrial pump); 7 for continuous/residential use

$/kWh

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⚡ Test your knowledge
NEC Article 220 was renumbered in the 2026 code cycle. What is the new article number?
  • A. Art. 100
  • B. Art. 120
  • C. Art. 200
  • D. Art. 230
💡 NEC 2026 renumbered Article 220 (Branch-Circuit, Feeder, and Service Calculations) to Article 120.
Energy Management Systems were moved from Article 750 to which article in NEC 2026?
  • A. Art. 100
  • B. Art. 125
  • C. Art. 130
  • D. Art. 150
💡 NEC 2026 moved Energy Management Systems from Article 750 to Article 130.
Which NEC standard size overcurrent device comes after 90A?
  • A. 95A
  • B. 100A
  • C. 110A
  • D. 105A
💡 Per NEC §240.6(A), the standard sizes are …90, 100, 110, 125… There is no 95A standard size.

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How it works & the NEC rules behind it

Understanding the electrical operating cost of motors, HVAC heat pumps, servers, lighting, and industrial machinery is essential for electrical estimators, engineers, and facility managers.

How Energy Cost is Calculated:

  • 1. Power to Kilowatt-Hours (kWh):
    Energy (kWh/day) = [ Power (Watts) × Operating Hours/day ] ÷ 1,000.
  • 2. Operating Expense ($ Cost):
    Monthly Cost ($) = Daily kWh × 30.4 Days/month × Utility Rate ($/kWh).
    Annual Cost ($) = Daily kWh × 365 Days/year × Utility Rate ($/kWh).
  • 3. Typical US Utility Rates (EIA Averages):
    • US National Average: $0.165 / kWh
    • Commercial Average: $0.132 / kWh
    • Industrial High-Volume: $0.089 / kWh
    • High-Cost Regions (CA, NY, MA, HI): $0.28 – $0.44 / kWh

Formulas & equations

Daily Energy (kWh) = (Power in Watts × Hours per Day) ÷ 1,000 Annual Cost ($) = Daily Energy (kWh) × 365 Days × Utility Rate ($/kWh) Carbon Footprint (lbs CO2) = Annual kWh × 0.85 lbs CO2/kWh [EPA eGRID]

NEC reference table

Appliance / Equipment Typical Power Daily Use Est. Monthly Cost (@ $0.16/kWh)
Central AC / Heat Pump (4-Ton)4,500 Watts8 Hours/day$175.00 / month
Electric Water Heater (50-Gal)4,500 Watts3 Hours/day$65.60 / month
EV Level 2 Charger (40A / 9.6 kW)9,600 Watts3 Hours/day$140.00 / month
Server Rack / Crypto Miner (2 kW)2,000 Watts24 Hours/day$233.30 / month
LED High-Bay Lighting (10 Fixtures)1,500 Watts10 Hours/day$73.00 / month

Worked example, step by step

Example: Annual Operating Cost of a 20 HP Industrial Pump Motor

Motor: 20 HP Motor (16.8 kW continuous draw), running 16 hours/day, 5 days/week, at $0.12/kWh industrial utility rate.

  • 1. Daily & Annual kWh: 16.8 kW × 16 hours = 268.8 kWh/day, prorated to 5 of 7 days/week over the year = 70,080 kWh / year.
  • 2. Annual Energy Cost: 70,080 kWh × $0.12/kWh = $8,409.60 per year.
  • 3. 10-Year Lifetime Operating Expense: $84,096.00 (roughly 20× the purchase price of the motor itself!).

Frequently asked questions

1 Horsepower (HP) = 746 Watts (0.746 kW). To account for standard electric motor efficiency (typically 85% to 92%), divide by efficiency: kW = (HP × 0.746) ÷ Efficiency.

Kilowatt (kW) measures real instantaneous power demand (the rate at which electricity is consumed), whereas Kilowatt-hour (kWh) measures total energy consumption over time (kW × hours).

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