Check My Math please - The Planted Tank Forum
Old 02-11-2007, 01:07 AM Thread Starter
Algae Grower

Join Date: Jan 2007
Location: Dallas, TX
Posts: 25

I have just received my electric bill for this month. It has doubled from \$62 in December to \$122 in January. I changed my light from a 15W from the pet store to an AH supply 36W Bright right at the beginning of January. This is probably the heating in my apartment which isn't working right, but I wanted to check that it isn't the light.

Billing Period: 28 days
Price per KWh: 14.4 cents (average)
Light Hours per day: 12 (it is less than this but lets err on the large side)

Now according to my math this should be

36/1000 = 0.036 KW/h
0.036 * 28 * 12 = 12.096 Kwh
(12.096 * 14.4c) / 100 = \$1.74

Seem right?
crisps is offline

Old 02-11-2007, 01:41 AM
Wannabe Guru

Join Date: Oct 2005
Location: Chicago
Posts: 1,945
check your bill, I bet they came out and didnt estimate this time. I they probably misread by 1000kwh.

Peace,
Ry

I raise my sword in the air in the battle against clado. I have been beaten in this battle but the war is not over. As my wounds heal I amass another army, an army with many legs, an army of Amano's......

I thrust my tridant into the mass of medusa like staghorn. I am wounded but I refuse to take a knee.
Ryzilla is offline
Old 02-11-2007, 02:06 AM Thread Starter
Algae Grower

Join Date: Jan 2007
Location: Dallas, TX
Posts: 25
Cheers

Cheers,

Just found out that someone else in my apartments had got one for over \$1000. That is more than the rent.
crisps is offline

Old 02-11-2007, 03:47 AM
Planted Tank Guru

Join Date: Dec 2005
Location: Sacramento, CA
Posts: 21,012
Without even looking at your math I can tell you that a 36 watt bulb left on 24/7 would not raise your electric bill that much. Two things (at least) could have happened: you have a program where you pay about the same every month for electricity, the average monthly use, but at the end of the year they make you catch up by putting all of the amount not yet paid on the one bill (this happened to me). Or, you have at least some of your heat from an electric heater, and the cold weather made it work hard. A 1500 watt heater can quickly drive up the bill.

Hoppy
Hoppy is offline
Old 02-13-2007, 07:39 PM
Planted Member

Join Date: Jul 2003
Location: Charlotte, NC, USA.
Posts: 190
The 36 watt fixture isn't 100% efficient, so maybe use 42-46 watts for an estimate of power usage (just a guess). Some goes off in the form of heat.

Still a fairly small amount of power usage compared to a \$112 bill. A desktop computer turned on 24/7 will suck up more power.
csf is offline
Old 02-13-2007, 07:49 PM
Wannabe Guru

Join Date: Sep 2004
Location: Seattle, WA
Posts: 1,666
Checks out (with unit analysis)

Quote:
Originally Posted by crisps View Post
36W/1000 = 0.036 KW
0.036KW * 12 hr/day * 28 days = 12.096 Kwh
12.096Kwh * \$0.144\$/Kwh = \$1.74
You need to factor in the filter (24hr/day) a heater (?hr/day) etc but the difference between a 15W and 36W lamp is not the sole factor in your increased bill.

I am still looking for a kill-a-watt to measure actual power consumption but I doubt that it is as bad as CSF's approximation. (Ie the advance 4X 32W T8 draws ~8W with no bulb connected)

Moved to Tucson.
BlueRam is offline
Old 02-13-2007, 08:11 PM
Planted Tank Enthusiast

Join Date: May 2004
Location: Oshkosh, WI
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Kevin

72g bowfront planted, CO2, 4x - T5HO, Eheim 2213 and 2217, 2 angels, pristella tetras, blue tetras, betta, albino bristlenose pleco, albino cories. Sword, vals, hygros, ludwigias, java moss and fern, anubias

2g Mac-quarium. Clown gravel, fluorescent plastic plants, and 2 guppies.
KevinC is offline
Old 02-13-2007, 08:41 PM
Planted Tank Enthusiast

Join Date: Oct 2005
Location: San Jose, CA
Posts: 786
Our january bill is always much higher and this year was especially cold. Your computer uses more electricity than that. Keep in mind they estimate usage every other month and then you make up the difference the next month. Look at the electric bill from last year and see how much you used, probably not that much different.
cbennett is offline

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