Grade three math to figure out KWH's

[Huck50]

Hi: Let's say my hydro costs 11 cents per kilowatt hour, all included and my toaster oven uses 1000 watts and it is in use for one hour...that would cost 11 cents?. How about my stereo which uses 250 watts, for one hour 11 divided by four=2.75 cents?. If I listen for four hours it costs 11 cents!!? Thanks, Huck

[Bill190]

It's too early in the morning to think!

How about this calculator instead...
(Enter watts, then hour's or whatever in the center.)
Online Conversion - Watt Calculator

Here is another to convert amps to watts, use Single Phase...
Power Calculators for quick conversions.

[John Nelson]

Yes, your calculations are correct. But it's amazing how quickly a whole bunch of those 11 cents add up to real money.

And typically your electric bill includes some sort of flat rate on top of which those 11 cents add.

And make sure your figure of 11 cents per KWH includes all those taxes and surcharges.

[Rick Johnston]

Originally Posted by John Nelson

it's amazing how quickly a whole bunch of those 11 cents add up to real money.

You got that right, John! And it works in reverse, too.

My first-ever under-$100 electric bill in 8 years was last month. We accomplished it by simply turning lights off when they weren't in use. I figured that at any given time, we were pulling a couple hundred unnecessary kwh. Here's how stupidly simple it was to save about $40 a month:
-- Turn off the halogen under-cab lights in the kitchen in the evenings. They look nice when we walk into the kitchen, but if we're in another room, no one is there to see.
-- Turn off the dimmed rope lights above the kitchen cabs in the evenings. See above.
-- Unplug ten 7-watt night lights plugged into outlets in rooms that don't need them.
-- Turn all of the outside lights off unless I'm expecting someone to visit.
-- Shut the computers down. A two-minute wait for them to boot is much more economical than leaving them on.

How stupid is that? And why didn't I do it six years ago?

[Tolyn Ironhand]

My one boss has a saying, "If electric is penny cheap, then why is my electric bill so high?"

[Bill190]

Each time my electric rates go up, I find something else to put on a power strip and switch off when not in use.

When I get around to remodeling my kitchen and rewiring, I will have 4 switches on the wall instead of one.

-Kitchen lights
-Microwave (always uses power even when off)
-Countertop outlets-A*
-Countertop outlets-B*

*Counter top outlets have GFCI's which always use a little electricity, then many counter top appliances always use a little electricity when "off".

So flip off all 4 switches and everything in the kitchen is "off" including the GFCI's!

[Tolyn Ironhand]

Good idea but, I hope you don't mind resetting clocks.

[Bill190]

Originally Posted by Tolyn Ironhand

Good idea but, I hope you don't mind resetting clocks.

I live in a rural area and out power goes out about twice a month quite regularly. So I have long ago given up on any 120V clocks. Mine are all battery!

[cwbuff]

Lights are obvious money wasters. Other household appliances when idle are less so. Quiescent currents in small items like microwave clocks, computers in power saver mode, phones etc. are miniscule (probably milliamps for some, microamps for others) when compared to the real power eaters in the home. One extra load in an electric cloths dryer will probably eat up any savings realized from shutting off your computer.

My computer in sleep mode uses around 8 watts. That figures out to be 66 cents per month (using the OP rate). Microwaves and VCR/DVD players typically use less than 5 watts, that's about 40 cents per month. In contrast an electric clothes dryer costs more than $8 monthly, the fridge around $25 and the water heater a whopping $38. A single 100 watt bulb left on for the entire month would cost $8.

I'm not sure about GFI waste. This is the first time I've heard of that. I would guess that waste would have to be less than the 5 mil trip level.

[Bill190]

If it is new construction and the wiring can be designed to save energy for little or no additional cost, then I think it is a good idea to do so.

All this little stuff adds up. Here someone determined just how much all these little things use...
(Pages 8 and 9)
http://enduse.lbl.gov/info/ACEEE-Leaking.pdf

[furd]

Doing some very rough calculations I suspect my "standby" load is somewhere near 20% of my consumption, about 2kwh daily. I'll do some meter checking in the next week or so to confirm or disprove this assumption.

[Bill190]

FYI the "Watt Calculator" above has a bug. When you select "Years", it gives the wrong results.

Instead enter 12 and select "Months".


For the geek types, you can save the file and change the code for line 575 (years) to...

else if (i == 5)

instead of... else if (i == 3)

[cwbuff]

I just inventoried my standby load. I used the numbers given on the product chart provided by Bill's link except for those itrems that I had specs on. My total load was around 76 watts. Higher than I expected, but the real surprise was GFI's. Using the 0.8 watts provided in the chart (it's a very limited sample so it may be wrong) my GFI's (20) comprise over 20% of the total. The only other item that was near that level was my cable DVR at 10 watts.

Even with the surprises, the bottom line (at least for me) is that standby power consumption on an individual residence basis is minor when compared to the real energy hogs. The 76 watts is about 0.3% of my daily usage. Using the 11 cents/kw it would cost about $6 a month.

Saving that $6 is problematic though. Not all GFI's can be eliminated, and reboot times on computers and DVR
offset any savings (my time is worth more). The same is true for routers and modems. Things like wireless phone and tool battery chargers can't be turned off. I don't know if cold starting the newer LCD TVs is a good thing, but the 30 or 40 cents saved monthly is hardly worth it.

The biggest energy waster in my home is an electric hot water heater. Even so, it's fairly new and it doesn't make sense to replace it -yet.

[Bill190]

Something interesting about GFCI's is that they continue to use power even if tripped! The internal circuits are connected directly to the hot lug.

If you have GFCI's on an outdoor circuit and only use these in the summer, then that circuit could be turned off for the winter.

For a bathroom, the GFCI could be wired (remodel/new construction) so that the outlet was only on when the light was switched on.

Then for something like a 50 story highrise, there would be 100 bathrooms, two to each floor. You could use occupancy sensors for the lights and the GFCI outlets. So the savings could add up for certain commercial/industrial situations.

[ByteWrangler]

Except people do things like recharge shavers on those bathroom GFCIs, and having to keep the light on to do so wouldn't be so great. Some like having a night light in there, too. It makes it easier for kids and guests to find the light switch.

I personally detest switched receptacles. IMO, they should always be on unless they are for some specific, unusual, purpose.

.8 W @ $0.11/kwh = $0.0021/day = 77¢ per year.

[Strategery]

It gets tricky to calculate things that cycle on and off or otherwise have an inconsistent draw. Your calculations can tell you the maximum cost, but for a more precise result you can buy products that will measure power usage (much like the power company), either for a single appliance or your whole house.

5 watts may sound like a small amount of power, but consider this: I have a solar panel that is rated at 15 watts but measures 1 foot by 3 feet. Spread over a 24 hour period, it may put out 5-10 watts "continuously", depending on the time of year. Add up all these "parasitic" loads, times every household equals a lot of wasted power. Does knowing the cost change my behavior? Not really; I live in an area that has some of the lowest electric rates in the country.

[Strategery]

Bill, keep in mind, occupancy sensors will use power too. Looking around the net, a vacancy sensor is the way to go. It will not waste power by turning on (even if it's not needed) but it will turn off a light (or appliance) if someone forgets to.