What is the general lighting load horsepower (HP) limit used for calculation?

• A. 1/8 HP
• B. 1/4 HP
• C. 1/2 HP
• D. 1 HP

Answer: (A)

For sizing loads, lighting is often represented by a small, fixed horsepower value so you can mix it with motor loads without needing exact fixture wattages. The standard limit used for general lighting load calculation is 1/8 HP, which is about 93 watts. This conservative baseline ensures even minimal lighting contributes to the overall size of the service or feeders without overestimating demand. Using a larger figure would overstate the lighting demand, while this 1/8 HP figure is a conventional, commonly accepted allowance in calculations and exams. In real practice you might work with watts or VA per square foot, but the 1/8 HP assumption is a traditional simplification for quick HP-based calculations.