audit-energy-consumption

Audit Energy Consumption

Systematically assess where and how energy is consumed across a facility or operation to identify waste, prioritize upgrades, and establish a measurement baseline for efficiency programs.

Why This Is Best Practice

Adopted by: U.S. Department of Energy Better Buildings program (covering 13% of U.S. commercial building space), EPA ENERGY STAR (certified 40,000+ buildings and plants), EU Energy Efficiency Directive (mandatory energy audits for large enterprises), ISO 50001 certified organizations in 170+ countries, ASHRAE (professional standard for commercial auditing). Impact: ASHRAE research shows Level II energy audits identify savings opportunities averaging 15–30% of energy costs. EPA ENERGY STAR buildings use 35% less energy than typical buildings (EPA 2023 data). ISO 50001 certified organizations achieve average energy intensity improvements of 10–15% within 3 years. DOE Better Buildings challenge participants saved $15 billion in energy costs and 7.4 quadrillion BTUs over 10 years. Why best: Most organizations reduce energy costs by optimizing what they already have — HVAC scheduling, lighting controls, equipment setpoints — before capital investment. An audit quantifies the opportunity in each system so resources target the highest-ROI improvements first. Without a baseline audit, efficiency programs lack the measurement foundation to claim savings or set credible targets.

Sources: ASHRAE Standard 211-2018; ISO 50001:2018 §9.1; EPA ENERGY STAR Portfolio Manager Technical Reference; DOE Better Buildings Industry Partner resources; EU Energy Efficiency Directive 2012/27/EU (amended 2018)

Steps

1. Define audit scope and level — Determine audit depth: Level I (walk-through, utility bill analysis, identify obvious opportunities), Level II (detailed survey, energy calculations, cost-benefit for each measure), or Level III (investment-grade, sub-metered measurements, simulation model). Scope should match the investment decision being made.
2. Collect utility data — Gather 24 months of energy bills (electricity, gas, water, steam) from all utility accounts. Calculate energy use intensity (EUI = kBtu/sq ft/year). Compare to CBECS median for building type — this benchmarks performance before stepping inside.
3. Conduct site walkthrough — Inspect all major energy-using systems: HVAC (age, controls, setpoints, runtime), lighting (type, controls, hours of operation), plug loads (always-on equipment), building envelope (insulation, window condition, air leakage), and process equipment. Note operating hours and occupancy patterns.
4. Collect interval data — For Level II/III, obtain 15-minute interval electricity data from the utility. Plot against degree days and occupancy schedules. The baseload (minimum consumption) reveals always-on loads; slope reveals HVAC efficiency.
5. Identify and quantify improvement opportunities — For each system, calculate current energy use, post-upgrade energy use, and annual savings. Apply simple payback and NPV calculations. Group measures: operational (no-cost/low-cost), capital (moderate payback), and major retrofit (long payback).
6. Benchmark against standards — Compare EUI to ASHRAE 90.1 baseline, EPA ENERGY STAR median, and sector peers. Identify which systems perform worst relative to benchmarks — these are priority targets.
7. Prioritize by ROI and implementation difficulty — Rank measures by: (1) operational changes first (free savings), (2) low-cost upgrades under 2-year payback, (3) capital investments under 5-year payback, (4) deep retrofits. Co-benefits (comfort, compliance, carbon) adjust ranking.
8. Document findings in audit report — Write: executive summary with total savings potential and cost, system-by-system findings, measure list with costs/savings/payback, implementation roadmap, and measurement and verification plan.

Rules

• Always collect 24 months of utility data before the site visit — one year misses seasonal patterns; two years catches anomalies.
• Calculate EUI before entering the building — knowing how the facility benchmarks against peers focuses the walkthrough on the highest-impact systems.
• Separate operational measures from capital measures — operational savings are available immediately; mixing them with capital improvements obscures quick wins.
• Include a measurement and verification plan — savings claims without a post-implementation measurement protocol are unverifiable and erode stakeholder trust.

Common Mistakes

• Auditing without occupancy schedule — A facility that runs 24/7 has completely different optimization levers than one operating 8 hours/day. Never assess equipment runtime without mapping occupancy.
• Ignoring plug loads — In modern offices, plug loads (computers, monitors, kitchen equipment) can represent 30–40% of consumption. Most audits undercount them.
• Treating HVAC setpoints as fixed — Setpoint schedules are the highest-ROI operational change in most buildings. Auditors who don't access the BMS miss the largest no-cost opportunity.
• Reporting savings without baseline measurement period — Claimed savings are invalid without a documented pre-audit baseline. Establish the measurement boundary before the audit, not after.

Examples

Office building Level II audit: 50,000 sq ft office, EUI 85 kBtu/sq ft vs. 60 median. Audit finds: HVAC runs nights and weekends (setback scheduling = $18K/year savings, 0-year payback), T12 fluorescent lighting (LED retrofit = $22K/year savings, 3.2-year payback), server room over-cooled (setpoint raise = $6K/year savings, 0-year payback). Total: $46K/year, blended payback 2.1 years.

Manufacturing plant: Process steam system audit reveals $90K/year in steam trap losses. Trap survey + repair program: $12K cost, 0.13-year payback. ISO 50001 implementation improves tracking for regulatory reporting.

When NOT to Use

• When a building is scheduled for demolition or major redevelopment — energy efficiency investments won't be recovered.
• When a Level I audit has already been completed in the past 2 years with no major operational changes — start with implementing the existing recommendations before re-auditing.
• When the primary goal is carbon reporting rather than cost reduction — carbon accounting follows a different methodology (GHG Protocol Scope 1/2/3) and requires different data collection.