Green Building Calculator Formula

Understand the math behind the green building calculator. Each variable explained with a worked example.

Use the Green Building Calculator

Formulas Used

Annual Energy Savings

annual_energy_savings = saved_kwh * elec_rate

Energy Saved

kwh_saved = saved_kwh

Water Saved

water_saved = saved_water

CO2 Reduced

co2_reduced = saved_kwh * 0.92 / 2204.6

Variables

VariableDescriptionDefault
building_sqftBuilding Size(sq ft)5000
energy_savings_pctEnergy Savings(%)30
water_savings_pctWater Savings(%)40
elec_rateElectricity Rate(USD/kWh)0.15
baseline_kwhDerived value= building_sqft * 15calculated
saved_kwhDerived value= baseline_kwh * energy_savings_pct / 100calculated
baseline_waterDerived value= building_sqft * 20calculated
saved_waterDerived value= baseline_water * water_savings_pct / 100calculated

How It Works

How to Calculate Green Building Savings

Green buildings use less energy, water, and resources than conventional buildings.

Formula

Energy Saved = Building Size * Baseline EUI * Energy Savings %

Baseline EUI: ~15 kWh/sq ft/year for commercial, ~6 kWh for residential

Green Building Benefits

  • Energy: 25-50% reduction from insulation, HVAC, lighting
  • Water: 20-50% reduction from low-flow fixtures, rainwater
  • Waste: 50-75% construction waste diversion
  • Health: Improved indoor air quality and daylight

    • Worked Example

    A 5,000 sq ft green office saving 30% energy and 40% water at $0.15/kWh.

    building_sqft = 5000energy_savings_pct = 30water_savings_pct = 40elec_rate = 0.15
    1. 01Baseline energy: 5,000 * 15 = 75,000 kWh/year
    2. 02Energy saved: 75,000 * 30% = 22,500 kWh
    3. 03Annual savings: 22,500 * $0.15 = $3,375
    4. 04CO2 reduced: 22,500 * 0.92 / 2,204.6 = 9.39 metric tons

    Ready to run the numbers?

    Open Green Building Calculator