Electrical energy; classes of consumers and demand

Electrical energy is the energy carried by the flow of electric charge, i.e. the work done by electric power over time: $E = P \times t$, measured commercially in kilowatt-hours (kWh, a "unit"). It is produced by converting other forms (hydro, thermal, solar, wind, nuclear), transmitted over lines, and converted back at the consumer into mechanical work (motors), heat, light, sound or chemical energy.

Classes of electrical consumers and their demand

Utilities group consumers by the nature of their use, load pattern and supply voltage. The main classes (also the basis of NEA tariff categories) are:

1. Domestic (residential) consumers

• Loads: lighting, fans, TV, refrigerator, water heater, induction cooker, iron, pumps.
• Demand: small connected load (typically 0.5 to 10 kW), single-phase 230 V (three-phase 400 V for large houses).
• Peak in the evening (about 5 to 10 pm); low load factor (about 10 to 20 %), high diversity.

2. Commercial consumers

• Shops, offices, hotels, hospitals, banks, malls, cinemas.
• Loads: lighting, air-conditioning, lifts, computers.
• Demand: medium; peak during working hours; load factor about 25 to 40 %; supplied at 400 V or 11 kV.

3. Industrial consumers

• Small industries (up to about 50 kW): 400 V three-phase.
• Medium industries (about 50 kW to 1 MW or more): 11 kV.
• Large industries (MW range: cement, steel, paper): 33 kV, 66 kV or 132 kV.
• Loads: motors (largest share), furnaces, welding, electrolysis.
• Demand: large; high load factor (60 to 80 % for continuous-process plants); reactive power demand due to induction motors.

4. Agricultural (irrigation) consumers

• Pumps for irrigation, agro-processing.
• Demand: seasonal (dry season), low load factor.

5. Public services

• Street lighting: night only, fixed hours; predictable load.
• Water supply and sewage pumping: fairly continuous.
• Traction (trolley bus, electric railway, EV charging stations): fluctuating load.

6. Others: temples and religious places, community consumers, government institutions, bulk supply to other utilities.

 Load (MW)
   |           industrial ______________
   |   ____/~~~~~~~~~~~~~\        /\ <- domestic
   |__/                    \______/  \_ evening peak
   +---------------------------------------> hour
   0     6      12      18     24

Knowing each class's demand helps the utility forecast load, size generation and network, set tariffs, and apply demand side management to flatten the evening peak.