Maximum Demand is the highest average load (in kW, kVA, or A) that an electrical installation draws over a specified time interval (typically 15, 30, or 60 minutes) within a billing period.
(not the 500 kW spike). 5. Software & Tools Review | Tool | Type | Best for | Accuracy | Cost | |------|------|----------|----------|------| | Excel (manual) | Spreadsheet | Simple estimates, learning | Low | Free | | ETAP / DIgSILENT | Professional power system | Complex industrial MD & load flow | High | $$$ | | Ecodial (Schneider) | Free tool | LV installation & MD estimation | Medium | Free | | PowerLogic ION Setup | Meter configuration | Real MD from meters | Very high | Varies | | OpenDSS | Open source | Distribution ADMD studies | High | Free | Reviewer note: For most facility managers, the best tool is already inside your energy meter (e.g., Schneider PM5500, Siemens PAC4200, or simple utility meter). Learn to read its MD registers. 6. Common Mistakes & Pitfalls | Mistake | Consequence | |---------|--------------| | Using instantaneous peak instead of averaged demand | Oversized equipment, higher capital cost. | | Ignoring power factor | MD in kVA may exceed kW MD – paying for reactive power. | | Wrong demand interval | 30 min vs 15 min changes MD significantly (shorter = higher). | | Not updating diversity factors | Older buildings have different load patterns today. | | Forgetting seasonal variation | Summer MD (AC) vs winter MD (heating) can differ 2x. | 7. Real-World Case Study Problem: A hotel had monthly demand charge of $18/kW. Their MD was 450 kW (metered). Energy manager staggered pool pumps, laundry, and kitchen exhaust fans. max demand calculation
| Time | Instant kW | Avg over last 15 min | |------|------------|----------------------| | 13:00 | 100 | 100 | | 13:05 | 300 | 200 | | 13:10 | 500 | 300 | | 13:15 | 200 | 275 (13:00–13:15) | | 13:20 | 400 | 350 (13:05–13:20) ← | | 13:25 | 100 | 300 | Maximum Demand is the highest average load (in