Energy Auditing Methodology and Standards
The audit as a structured process
A compliant audit follows a defined sequence: data collection (bills, drawings, nameplate data, operating schedules), walk-through and inventory, measurement, energy balance and disaggregation, identification of measures, and reporting. Bulgarian practice aligns with the EN 16247 series (general requirements, buildings, processes, transport) and, for enterprises, with the requirements that audits be proportionate, based on measured/verifiable data, and traceable. Understand top-down vs. bottom-up approaches and the energy balance concept: energy in = useful output + losses, with losses split into envelope, ventilation, distribution, and control.
Key methodological concepts
- Baseline and normalization: degree-day correction, production normalization for industrial audits.
- Sampling and metering: spot measurements vs. continuous monitoring; instrument accuracy and calibration.
- System boundaries: what is inside the audit scope (e.g., tenant consumption, on-site generation).
- Uncertainty: stating assumptions and data gaps explicitly.
Traps in questions
Questions love to test whether you know an audit is not just a checklist of technologies - it must quantify current consumption and savings with stated assumptions. Another trap: treating nameplate ratings as actual consumption (load factor and hours of use matter). Also distinguish an energy audit from an energy review under an energy management system and from a walk-through survey.
Worked example / rule of thumb
For a quick estimate of annual electricity for a motor: kWh ≈ rated kW × load factor × operating hours. A 15 kW motor at 0.6 load factor running 3,000 h/yr uses ≈ 27,000 kWh. Use measured power where available; nameplate alone overstates.
Reporting
Reports must state scope, methodology, baseline, findings, prioritized measures with savings and costs, and measurement/verification approach.