Energy: The Largest Operating Cost
Energy typically accounts for 25-40% of building operating costs. In Bangladesh, with rising electricity tariffs and growing ESG expectations, energy management is no longer optional — it's a strategic priority. The good news: most buildings have 15-30% energy savings potential through no-cost and low-cost measures alone.
Energy Use Intensity (EUI) Benchmarks
| Building Type | Good (kWh/m²/yr) | Average | Poor | Notes |
|---|---|---|---|---|
| Office — fully AC | 100-150 | 150-250 | >300 | Includes server rooms, lifts |
| Office — mixed mode | 60-100 | 100-150 | >200 | Natural ventilation + AC zones |
| Retail | 150-200 | 200-350 | >400 | High lighting and HVAC load |
| Hotel | 200-300 | 300-450 | >500 | 24/7 operation, high services |
| Hospital | 250-350 | 350-500 | >600 | Critical systems, 24/7 |
| Warehouse | 20-40 | 40-80 | >100 | Minimal HVAC unless cold storage |
| Factory | Varies widely | Process dependent | — | Benchmark by production unit, not area |
| Data Centre | PUE 1.2-1.4 | PUE 1.4-1.8 | PUE >2.0 | Use PUE, not EUI |
Typical Energy Breakdown — Office Building
| System | % of Total | Savings Potential | Key Measures |
|---|---|---|---|
| HVAC | 40-55% | 15-30% | Temperature setpoints, scheduling, VFD, chiller optimisation |
| Lighting | 15-25% | 30-60% | LED retrofit, occupancy sensors, daylight harvesting |
| Plug loads | 15-20% | 5-15% | Equipment efficiency, power management, timer controls |
| Lifts | 5-10% | 10-30% | Regenerative drives, traffic analysis, standby mode |
| Pumps/fans | 5-10% | 20-40% | VFD installation, right-sizing, impeller trimming |
| Other | 5-10% | Variable | DHW, exterior lighting, miscellaneous |
Quick Wins — No/Low Cost
- Temperature setpoint adjustment — every 1°C increase in cooling setpoint saves 3-5% of HVAC energy. Set 24°C instead of 22°C.
- Operating schedule alignment — HVAC running after hours wastes 10-15% of energy. Programme to match actual occupancy.
- Lighting schedule — exterior and common area lighting on timers/sensors. Don't light empty spaces.
- Equipment standby — turn off unused equipment. A single PC left on overnight costs ~BDT 3,000/year.
- Filter maintenance — dirty AC filters increase energy consumption by 5-15%. Clean monthly.
- Chilled water temperature — raise chilled water setpoint from 6°C to 7°C — saves ~3% chiller energy.
Energy Audit Process
| Level | Scope | Output | Cost | When to Use |
|---|---|---|---|---|
| Walk-through (Level 1) | Visual inspection, utility bill analysis | Preliminary report, quick wins identified | Low (BDT 100-300K) | Initial assessment, new tenancy |
| Standard (Level 2) | Detailed analysis, sub-metering data, system performance | Detailed report with ECM list, payback analysis | Medium (BDT 300-800K) | Comprehensive improvement plan |
| Investment Grade (Level 3) | Full engineering analysis, monitoring, M&V plan | Bankable report for financing energy projects | High (BDT 800K-2M+) | Major CAPEX decisions, ESCO projects |
Sub-Metering Strategy
"You can't manage what you can't measure." Sub-metering is essential for identifying where energy is consumed and where savings opportunities exist.
- Minimum: Main incomer, generator, HVAC (chiller/AHU), lighting, lifts, tenant floors
- Better: Add individual chillers, cooling towers, major AHUs, server room, water heating
- Best: Add floor-level metering, individual tenant meters, real-time dashboards
References
Insights & Guidance
- Energy is 25-40% of building operating cost. Most buildings have 15-30% savings potential from no/low-cost measures.
- Good office EUI: 100-150 kWh/m²/yr. Average: 150-250. Poor: >300. Measure and benchmark yours.
- HVAC is 40-55% of building energy. Temperature setpoint (+1°C = -3-5%) and schedule alignment are the quickest wins.
- Sub-metering is essential: "you can't manage what you can't measure." Start with main, HVAC, lighting, lifts.
- LED lighting retrofit delivers 30-60% lighting energy savings with 2-3 year payback.
Energy cost is the largest controllable operating cost in most buildings. With rising tariffs and growing ESG reporting requirements, a structured energy management programme reduces costs, carbon emissions, and regulatory risk simultaneously.
- No measurement — without sub-metering, you can't identify waste or verify savings.
- Comfort compromise — aggressive setpoint changes without occupant communication cause complaints.
- After-hours waste — HVAC running 24/7 when occupancy is 10hr/day wastes 30-40% of HVAC energy.
- Monthly energy consumption tracking (kWh, kWh/m²)
- Sub-metering data by major system
- Energy audit report with ECM list and payback analysis
- Energy reduction targets and progress tracking
- Are lights on in unoccupied areas?
- Is HVAC running outside occupied hours?
- Are there sub-meters installed and being read?
- What is this building's EUI (kWh/m²/year)?
- When was the last energy audit?
- Is there a sub-metering system?
- What energy reduction targets are set?
- Energy audit — certified energy auditor (CEM, CMVP).
- HVAC optimisation — mechanical engineer with BMS experience.
- LED retrofit — electrical engineer with lighting design experience.