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Field references
Quick-lookup tables for voltage systems, typical loads, cooling conversions, and diversity factors — handy while you're sizing something in the field.
Typical voltage systems
| System | Voltage | Common use |
|---|---|---|
| Residential single-phase | 120 / 240 V | US homes — 120V outlets, 240V dryers/ranges/EV chargers |
| Commercial three-phase | 208Y/120 V | Small-to-mid commercial buildings |
| Commercial/industrial | 480Y/277 V | Large commercial, industrial motors, LED lighting |
| Utility distribution | 4.16 kV – 34.5 kV | Medium-voltage feeders to substations |
| Data center IT gear | 208 V / 415 V | PDU and rack-level power distribution |
Typical appliance & device draw
| Device | Typical power | Notes |
|---|---|---|
| LED bulb | 8–12 W | Equivalent to a 60W incandescent |
| Refrigerator | 100–800 W running | Compressor cycles; average ~150W continuous |
| Central AC (residential) | 3,000–5,000 W | ~3–5 tons of cooling |
| Electric water heater | 4,000–4,500 W | Elements rarely run simultaneously |
| Level 1 EV charger | 1.4–1.9 kW | Standard 120V outlet |
| Level 2 EV charger | 3.3–19.2 kW | 240V, most common home/workplace charging |
| DC fast charger | 50–350 kW | Public/commercial rapid charging |
| Desktop GPU (high-end) | 300–600 W TDP | Per card, under full load |
| Data center rack (AI) | 10–130 kW | Varies widely with GPU density and cooling |
Cooling & HVAC quick reference
| Metric | Value | Notes |
|---|---|---|
| 1 ton of cooling | 12,000 BTU/h | ≈ 3.5 kW of heat removal |
| Electrical draw per ton | ~1–1.2 kW | Depends on chiller/compressor efficiency (COP/EER) |
| 1 kWh | 3,412 BTU | Standard energy-to-heat conversion |
| Residential AC sizing | ~400–600 sq ft per ton | Rough rule of thumb, climate-dependent |
| Data center PUE (good) | 1.2–1.4 | Modern hyperscale / efficient design |
| Data center PUE (legacy) | 1.6–2.0 | Older air-cooled facilities |
Solar & renewable quick reference
| Metric | Value | Notes |
|---|---|---|
| Peak sun hours (US average) | 3–6 h/day | Varies by latitude and climate |
| Residential panel output | 350–450 W | Per panel, standard test conditions |
| System efficiency (derate) | 75–85% | Inverter, wiring, soiling, temperature losses |
| Battery round-trip efficiency | 85–95% | Lithium-ion home storage systems |
Load diversity factors (planning estimates)
| Load type | Typical diversity factor | Notes |
|---|---|---|
| Residential dwelling units | 0.35–0.5 | Applied to connected load for feeder sizing |
| Small commercial (retail/office) | 0.6–0.8 | Depends on occupancy schedule |
| Data center IT racks | 0.9–1.0 | Compute loads run near-continuous, low diversity |
| EV charging depots | 0.5–0.8 | Depends on fleet scheduling and charger overlap |
Values above are typical planning estimates, not code minimums. For binding design work, confirm against the Standards library and manufacturer documentation.