PHCN measures its electrical energy in

Analyze the question PHCN (Power Holding Company of Nigeria) bills households for the electrical energy they use. The question asks which unit it uses to measure that energy.

Explain the concept

• Power is the rate of using energy. Its unit is the watt (W).
• Energy = Power × Time.
• The SI unit of energy is the joule (J), where 1 J = 1 W × 1 s.
• A joule is very small, so it is impractical for household billing. Electricity companies use a larger commercial unit, the kilowatt-hour (kWh).

Step-by-step solution

1. Option A, W (watt): This is a unit of power, not energy. Eliminate.
2. Option D, J (joule): This is the SI unit of energy, but it is too small for billing. 1 kWh = 1000 W × 3600 s = 3,600,000 J, so billing in joules would give enormous numbers. PHCN does not use it.
3. Option C, Wh (watt-hour): This is a valid unit of energy, but it is still too small for the amounts a household uses. Meters and bills do not use it.
4. Option B, kWh (kilowatt-hour): This is the standard commercial unit of electrical energy, and it is what appears on your electricity meter and bill.

Example: A 2000 W electric iron used for 3 hours consumes 2 kW × 3 h = 6 kWh.

Answer: The correct option is B, KWh.

Tip: Remember that "W is for Work-rate (power)" while "kWh is what the Light bill counts." If the question mentions energy bills or electricity meters, think kWh. Also note that J is the SI unit, while kWh is the commercial unit. JAMB often tests this difference.