How much energy is saved by replacing a 75-watt incandescent light bulb with an 18-watt fluorescent bulb over its lifetime?

To determine how much energy is saved by replacing a 75-watt incandescent light bulb with an 18-watt fluorescent bulb over its lifetime, it's essential to calculate the energy used by both types of bulbs.

First, consider the wattage difference. The incandescent bulb uses 75 watts, while the fluorescent bulb uses 18 watts. The difference in power usage is:

( 75 , \text{W} - 18 , \text{W} = 57 , \text{W} ).

Next, it is necessary to estimate the operational lifetime of the bulbs. A typical lifespan for incandescent bulbs is about 1,000 hours, while fluorescent bulbs can last approximately 10,000 hours.

Now, calculate the total energy consumed over their lifetimes. Energy (in kilowatt-hours) can be computed using the formula:

[ \text{Energy (kWh)} = \text{Power (kW)} \times \text{Time (h)} ]

For the incandescent bulb over 1,000 hours:

[ \text{Energy} = \frac{75 , \text{W}}{1000} \times 1000 , \text{h} =