[jfim]

The kilowatt hour is a fantastic unit when talking about electrical consumption.

Are you running a 100W load (0.1kW) for an hour? That's 0.1kWh. Running it for ten would make a whole kilowatt hour.

This allows for easy calculations of how much something is going to cost in electricity, and the units are such that it's easy to do the math in your head.

[andrewla]

You're using a toy example to strawman the Joule counterpoint. How much do you use in a month, which is the typical billing cycle? Off-peak vs. on-peak cost?.

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.

[trelane]

> You're using a toy example to strawman the Joule counterpoint.

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.

[MonkeyClub]

Same here, I find the KWh to be a very useful unit for daily calculations of that sort, where I want a quick upper bound on things to make estimations.

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".

[andrewla]

> 300W vs 65W

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.

[trelane]

I use watt when I want to compare power, and watt*hour when dealing with energy. Hours because hours are a lot closer to the real spans of time I use, and therefore much easier to calculate with. E.g. it's more common to run a 3kW AC for 3h than 3s. So, 9 kWh instead of 9 kWs (or 180kWs, for the same time span)

> If you're going to multiply by the electricity cost anyway

I don't usually convert to money. If it's a linear cost per kWh, then I can deal with that at the end or, more likely, don't actually really care.

The _actual_ cost you pay is often tiered anyway, so who knows what the price _actually_ is until you have the whole month's worth of power usage finalized. And then it's not clear what I could account to what tier.

> might as well break out the calculator one step early.

Bold to assume I use a calculator much.

[MonkeyClub]

Yeah exactly, I didn't even need to take time into account, I was looking for the upper bound presuming it's always on with a simple Wattage comparison.

But that was mostly because that workstation, albeit lovely, had a very long boot process.

The ThinkCentre boots in under a minute, so I actually end up only booting it when needed.

(Some of my work can be done offline, and I jump at every opportunity to `halt -p` and be in the quiet offline space/state.)

[2Gkashmiri]

>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.

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

[jfim]

To take your example, your 14 Watt lightbulb would use about 0.35kWh per day if running all day, or about 10kWh per month of nonstop usage. At 0.15$/kWh, that's about a dollar and fifty cents, assuming you'd want to leave it on all day and night.

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.

[andrewla]

I'll take one more shot at explaining why this continues to be a strawman.

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.

[jfim]

Maybe your utility company bills in joules, but mine does in kWh. You can easily figure how many kilowatts your bulb does (divide by 1000), and you can come up with an estimate of how many hours you use it in a day/month/year, which is then easy to turn into an actual dollar amount.

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.

[johnwalkr]

Hours are usually more convenient to work with than seconds when talking about energy use (even in this case when you are comparing to other things. Plus it's the de facto standard unit more people are familiar with. Power bills, electric car capacity, and energy efficiency are all normally described in kWh.

[andrewla]

This is true, but it is exactly what I am railing against. It's just tradition -- energy in houses is kWh, so let's use that for other things too.

Instead, let's just use Joules everywhere. Easy peasy. Why are my batteries rated in Ah -- it's not like they're providing a variable voltage source; just give me Joules.

I know this is a ridiculous hill to die on, but I will die on it!

[trelane]

> it's not like they're providing a variable voltage source; just give me Joules.

They are, technically. https://www.batterypowertips.com/how-to-read-battery-dischar...

Probably doesn't matter though. :)