Building Energy Audit Calculator

EUI measures how much energy a building uses per square foot per year, expressed in kBtu/sq ft/yr. It normalizes energy consumption across buildings of different sizes, making benchmarking meaningful. A lower EUI means a more energy-efficient building. Typical office EUIs range from 50–100 kBtu/sq ft/yr.

The most reliable source is 12 months of utility bills — add up your electricity (kWh) and natural gas (therms) totals. Many utilities also provide annual summaries online. If you have a building energy management system (BMS), it can export this data directly.

Studies by the U.S. Department of Energy suggest commercial buildings waste 20–30% of the energy they consume on average. Poor insulation, aging HVAC systems, inefficient lighting, and equipment left running during unoccupied hours are the primary culprits.

HVAC (heating, ventilation, and air conditioning) is the largest energy consumer in most commercial buildings, typically accounting for 35–50% of total energy use. Lighting is usually second at 20–35%, followed by plug loads and equipment.

Older buildings generally have less efficient envelope construction, outdated HVAC equipment, and older lighting systems. A building over 25 years old without major upgrades can consume 30–50% more energy than a modern equivalent. Energy audits help prioritize the upgrades with the best return on investment.

ENERGY STAR uses a 1–100 scale where a score of 75 or above qualifies a building for certification, meaning it performs better than 75% of similar buildings nationwide. Scores below 50 indicate significant room for improvement and typically signal high energy waste.

Start with the highest-priority systems flagged in the audit — usually HVAC upgrades, LED lighting retrofits, and envelope improvements like insulation or window sealing. Commission a professional energy audit for detailed recommendations, and consider setting reduction targets of 10–20% over 3–5 years.

This tool provides an estimate based on your inputs for floor area, energy consumption, and system breakdowns. It is designed for preliminary benchmarking and awareness. For a certified audit with actionable retrofit recommendations, engage a licensed energy auditor or ASHRAE Level I–III audit professional.