What Is A Kilowatt-Hour Anyway?

Is it possible my PowerMac, plus all of the peripherals uses one kWh? I leave it on all day long. . .

Well, Pepco has a "green power" option, I think I'll take it. After all, at that point my power use just makes green power a more attractive investment.

(yes I realise they abstract the green power bit; the point remains that they buy power from green sources at the same rate, in the same quantity, as we use it)

-RS

how do you calculate the Tonnes of c02e per KWH based. I've just started an working in the energy field and i have no idea where to find this information.

I'm going to claim BS on that "average American uses 600-800kWh/month. During the summer my 1700 square foot home used 2800kWh (first time paying the bill since moving). This seemed *extremely* high, so I did some investigating and did all I could to lower it.

Last month I was down to 900kWh. Quite a difference, except when you consider that during that entire time I didn't use my air conditioner once. I know now that my home is using about 900 kWh without the AC or heat. Where the hell is that coming from? I have no idea. I've been around the house measuring things with my Kil-o-watt meter and nothing should add up to that much.

My best guess is the laundry dryer (we don't use the dryer on the dishwasher) and the refrigerator. The fridge is rated at 850kWh/year and has an energy star logo on it so I don't think it makes much of a dent.

When I called the electric company, they told me that my house wasn't very different than the other houses in my neighborhood as far as consumption, so I don't think I've got anything out of the ordinary going on. I can't possibly imagine that the rest of the U.S. manages to get by on 600-800kWh when my home--even full of CFLs and no heat/AC--doesn't even touch that number.

It's not like I have a giant tesla coil in the back or anything. I wish I could plug my kil-o-watt into the dryer and the AC unit.

My California condo pulled 154 kWh last month, but I have gas hot water, stove, clothes dryer. I'm fortunate enough to live where I don't really need air conditioning or heat.

FWIW, I can add a couple more things to do with 1 kWh:

1 diswasher cycle (mine uses 0.62 kWh)
3 breadmaker cycles (mine uses 0.37 kWh)

And yes, that Kill-A-Watt monitor rules.

BTW, those "20 microwave meals" sound supsicious. The average microwave has to be close to 1000W now, which means 1 hour, which means 60/20 = 3 minutes zapping. What "meal" cooks in 3 minutes?

I'll have to ask Shea where he got the 600-800kwh figure, but please consider that even though 2800sq/ft might seem like the norm in your neighborhood, most americans don't like in such big houses, esp. in urban areas.

45 million people don't even have health insurance in the US, so I'd say that the average person probably doesn't live like you..

Watch out Rahul, the new dual G5 PowerMacs might pull close to a 1 kWh every hour, or 24 per day. The larger LCD displays also get quite warm.

I'll defer to anyone with a PowerMac and a Kill-A-Watt, but my guess is 20 kWh/day for mac and display.

(the G4 chip is another story, iirc quite efficient, so an Apple notebook or "mini" would do better)

Shea corrected his math; it is not 16 pounds but about 1.5 pounds per kwh.

I made a math boo boo. Visit here to see the full scoop, but each kWh of energy produces closer to 2 pounds of CO2, not 16.

Thanks to my commenter Hans for helping me catch my bad math.

Riskable, how do you heat your hot water?

I think you meant to write that the avg American household uses 600-800 KWH per month, not the average person.

I don't know where you people are getting your numbers from. This stuff is easy to estimate.

A kilowatt-hour is using 1000 watts of home electricity for one full hour. So that's the same as running 10 100-watt light bulbs for one hour -or- one 100-watt light bulb for 10 hours straight.

Lets figure this out for my work PC:

My computer has a 350 watt power supply (you can refer to your computer's specifications to figure this out), and my monitor is rated at 100 watts. So the system uses 450 Watts, i.e. .45 KWH. Multiply that 10 hours at work, and that's 4.5 KWH for a work day.

(the enlightened will note that my work PC probably uses only half or less than 350 watts under normal operating conditions. therefore, the average 10 hour day is more like 2.75 KWH, if not less)

To contrast, my Apple iBook uses a 65 watt power supply. You would have to use it for 20 or more hours to use 1 KWH.

I think during the spring and fall months when I don't have to run any HVAC, I use about 1-200 KWH. That's a small home with 2 people.

2800 KWH is ludicrous for a 1700 sq ft home. Make sure the electric company didn't misread the meter. Do you leave a few PCs on 24/7 ? Your AC or refrigerator might be broken too. 100 KWH a day

My hot water comes from a propane heater. The 2800kWh was during the month of July and it was about 95 degrees with 95% humidity pretty much every day, all day. It dropped to MAYBE the low 80s at night.

During that time, our thermostat was set to 75 degrees. I consider this the highest acceptable temperature for the summer months.

FYI: I've had the power company come and double-check the meter to make sure it wasn't broken.

Large appliances:

We have an 850kWh/year refrigerator. The ice maker is turned off and the thermostat for both the freezer and fridge are set to their factory settings. In theory, this should use 70.8kWh/month. Here's a brief summary of what I think are the big players in my bill:

Refrigerator: 70.8kWh/month (850kWh/year model)
Dryer: 50kWh/month (10 dryer cycles, estimated)
Dishwasher: 5kWh/month (we don't use the dry cycle anymore--we did during that big bill)
Computers: 216kWh/month (3 beefy machines and some equipment, I accept this as I need it for work. I try to shut them down when I can.)
750W Halogen light in the back yard: 90kWh (based on 120 hours of usage--I'm out there a LOT at night with the dog).
Oven/Stove: 200kWh/month (use them a LOT--to cook healthy dinners, sigh).

This leaves 350kWh that are unaccounted for. I can attribute 100 of that to misc lighting and my wife's power tools (she uses a lathe quite a bit--which I need to measure). But I also think that one of my big appliances is malfunctioning or is much more inefficient than it should be.

I have a Kill-A-Watt, so I've measured everything I can. This leaves things I CAN'T easily measure such as the stove/oven and the washer/dryer. Then there's things that I might be missing because I didn't measure them for a whole month. My fridge could be cycling like crazy while I sleep, or my computer could start crunching in the middle of the night. I dunno.

I'm trying to get my most power-hungry computer to go into sleep mode with wake-on-lan, but so far that has not been working.

I have no money right now, so purchasing new stuff (like a LCD to replace my beefy 22 inch CRT) has to wait.

A kilowatt hour, as explained above is using one thousand watts for an hour. In other units its about one horsepower for about 80 minutes, so one horse working pretty hard for that time. Or about 5 average people on bicycles pedalling pretty hard for a hour (200 watts each). Or about two lance armstrongs for an hour (500 watts). Now think about that next time you're at the gym. Too bad all that pedalling at the gym doesn't go into the power grid :)

500-800 kWh/mo. is very typical usage for a typical (~1500-2000 sq ft) home here in northern California, where we don't need much heat, and for the most part don't use AC at all. That said, many of the nicer homes around here use closer to 2000 kWh/mo, and one of my local customers has a 5000 sq ft home (I'm guessing) that uses upward of 4000 kwH/mo. The #1 "user" in the home is almost always the refrigerator, and I wouldn't use the Energy Star rating as any sort of a guide as to what it's actually using. Better plug that into your kill-a-watt meter and find out! After that, it's usually a deep freeze, or a pool or well pump, or a spa. If you've checked out all those things and you're still a lot of kW short of a power bill, check your home entertainment gear, and make sure your central air fan isn't the culprit. HTH.