| Primary value | 4.0 W / sqft (range 3 – 5 W/sqft built-up · mall 5–8 W/sqft) |
| Applies to | Office, retail, IT-park and institutional electrical sizing · Pre-tender connected-load estimate · Transformer, DG and service-connection sizing |
| Exceptions | General office → 3 – 4 W/sqft |
| IT building (high-density workstation) → 5 – 6 W/sqft | |
| Mall / retail (lighting + HVAC heavy) → 5 – 8 W/sqft | |
| Hospital → 5 – 7 W/sqft | |
| Hotel (per key) → 5 – 8 kW per room | |
| Diversity factor (commercial) → 0.7 – 0.8 | |
| Measured as | Total nameplate W ÷ built-up area in sqft. Higher than residential because of denser AC, lighting and equipment loads. |
| Source | NBC 2016 — Part 8, Section 2 📚 Cross-referenced |
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Commercial buildings draw 3–5× more electricity per sqft than residential because of HVAC, lighting and IT loads. Underestimating connected load is the most common cause of mid-project transformer upgrades — the additional substation costs ₹15–25 lakh and 8–12 weeks of utility approval.
MEP teams budget 4 W/sqft for offices, 5 W/sqft for IT, 6 W/sqft for malls, then apply a 0.7 – 0.8 diversity factor at the substation. A 100,000 sqft office park lands at ~400 kW demand, served by a 500 kVA transformer with a 250 kVA standby DG.