Energy Audit Calculator Formula

Understand the math behind the energy audit calculator. Each variable explained with a worked example.

Use the Energy Audit Calculator

Formulas Used

Energy Use Intensity

energy_intensity = kwh_per_sqft

Total Annual Energy Cost

total_cost = total_energy_cost

Potential Savings (20%)

potential_savings = total_energy_cost * 0.20

vs. Benchmark

vs_benchmark = (annual_kwh - benchmark_kwh) / benchmark_kwh * 100

Variables

VariableDescriptionDefault
annual_kwhAnnual Electricity Use(kWh)10800
annual_gas_thermsAnnual Natural Gas(therms)500
sqftBuilding Square Footage(sq ft)2000
elec_rateElectricity Rate(USD/kWh)0.15
kwh_per_sqftDerived value= annual_kwh / sqftcalculated
total_energy_costDerived value= annual_kwh * elec_rate + annual_gas_therms * 1.5calculated
benchmark_kwhDerived value= sqft * 4calculated

How It Works

How to Perform a Basic Energy Audit

An energy audit compares your actual energy use against benchmarks to identify saving opportunities.

Key Metric: Energy Use Intensity (EUI)

EUI = Annual Energy / Square Footage

Residential Benchmarks

  • Efficient home: 3-4 kWh/sq ft/year
  • Average home: 5-6 kWh/sq ft/year
  • Inefficient home: 7+ kWh/sq ft/year

    • Most homes can reduce energy use by 15-30% through basic efficiency improvements.

    Worked Example

    A 2,000 sq ft home using 10,800 kWh electricity and 500 therms gas annually at $0.15/kWh.

    annual_kwh = 10800annual_gas_therms = 500sqft = 2000elec_rate = 0.15
    1. 01Energy intensity: 10,800 / 2,000 = 5.4 kWh/sq ft
    2. 02Electricity cost: 10,800 * $0.15 = $1,620
    3. 03Gas cost: 500 * $1.50 = $750
    4. 04Total cost: $1,620 + $750 = $2,370
    5. 05Potential 20% savings: $2,370 * 0.20 = $474/year

    Frequently Asked Questions

    What is an energy audit?

    An energy audit systematically evaluates how a building uses energy and identifies opportunities to reduce consumption. Professional audits may include blower door tests and thermal imaging.

    What are the most common energy waste sources?

    Air leaks around windows and doors, poor insulation, inefficient HVAC systems, outdated lighting, and phantom loads from electronics are the top energy wasters in homes.

    How much can an energy audit save?

    Implementing recommendations from a professional energy audit typically reduces energy bills by 15-30%, saving $400-1,000 per year for an average home.

    Ready to run the numbers?

    Open Energy Audit Calculator