How much energy do you save per hour if you replace a 60-watt lightbulb with a 55-watt lightbulb?

That obviously depends on how much of the hour the light is turned on. Neither of them uses ANY energy when it's turned off.
The difference is (60 - 55) = 5 watts = 5 joules per second.
If the light is on for the entire hour, then the difference in energy is
(5 joule/second) x (3,600sec/hr) = 18,000 joules/hour .
Putting it in a more familiar unit . . .
(5 watts) x (1 hour) = 5 watt-hours = 0.005 Kilowatt-hour.
If your utility company charges you 25¢ per kilowatt-hour (a very high rate), then the more energy-efficient light bulb saves you (0.005) x (25¢) = 1/8 penny per hour of operation.

Answered by AL2006 | 2024-06-10

Replacing a 60-watt light bulb with a 55-watt light bulb saves 18,000 joules or 0.005 kilowatt-hours of energy per hour. This is a difference of 5 watts in power consumption. Hence, the energy saved is straightforwardly calculated from the power difference over time.
;

Answered by AL2006 | 2024-12-18