In the end there's no practical utility to this. We just pretend that we're living in a world where you get a 100W light bulb and know exactly what it will cost you, and not a world where half your bulbs claim to be 100W but are actually 14W with 100W-incandescent-equivalent and such.
Not a toy example. That's exactly how I estimate energy consumption for off the shelf devices. And for battery life (W*h but still).
> 100W light bulb and know exactly what it will cost you, and not a world where half your bulbs claim to be 100W but are actually 14W with 100W-incandescent-equivalent and such.
If you've lived with lighting you're responsible for, you've replaced bulbs. You know the different technologies and the packages say how much power they require.
Last year I switched off my fully-functional 2008 workstation (a lovely Fujitsu Celsius W370 on OpenBSD, a furry joy) because of such an upper bound difference (300W vs 65W for the ThinkCentre that hides among the books on my desk's side).
This sort of works in a similar way with light bulbs as well. Although lumen would be the appropriate unit for luminosity, the packaging uses wattage to indicate luminosity.
Although lumens and Watts are correlated, they aren't dimensionally equivalent as Joules and Watts are (CMIIW).
That "100W" on the package an electrically 14W bulb simply means "it's only using 14W, but shines like a 100W bulb, go ahead, BOGOF".
A watt to watt comparison is fine. Why hours? I can tell you right now that the big one uses ~4.5x the power. Is it really that much easier to convert the time you're using the device to seconds? If you're going to multiply by the electricity cost anyway, might as well break out the calculator one step early.
Where i live, the pricing is based on the amount of energy "consumed" during a month. plus we use 220v.
i use the kwh extensively, my induction cooker is rated at 1300Watts so i know by running it for 1 hour i am consuming 1.3kwh.
my monthly "consumption" before installing a 5kwh solar on-grid used to be around 300Kwh during summer months so over time i have learned to "reduce" my monthly usage, aka kwh by reducing my electric hot water geyser( going to solar water heater) (2kw geyser).
the kwh is definitely a good indicator for me
All of that math can be done in your head too, if you're willing to approximate the number of hours in a day to 25 and the numbers of days in a month to 30.
Why would I be running the light all day? The assumptions being made here are unrealistic enough that the answer becomes meaningless. The realistic question here, "how much money would I save by switching from a 100W incandescent bulb to a 14W LED bulb" is not helped by any of this kWh nonsense.
A joule is just a watt second instead of a kilowatt hour, and the 3600 factor (seconds per hour) is really annoying to use in mental math.
