can someone check my simple math for Porch lighting?

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RIGorous1

Platinum Member
Oct 26, 2002
2,053
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If I have a total of 400 watt on for 12 hours a day then that equals 400 watt-hours (?) x 12 = 4.8 Kilowatt-hours(?) per day

So if I multiply 4.8Kwh/day x 365 days then that equals 1752 Kwh per year

Assuming that my electric comany charges me $0.10 per Kwh that that means that I'm paying $175.2 every year on energy to keep this bulb on at night for 1 year ?

Does that number seem a bit high? I'm thinking of installing some porch lighting and I'm thinking that my number sounds kind of high just for electricity. Any of you have similiar wattage needs for porch lighting? or lighing in general? Does that number sound right? Do bulbs rated at 400 watts run at the full 400 constantly or do they run much lower?

Thanks
 

Put in a compact fluorescent and save yourself some cash.

EDIT: I've never seen a 400-watt light bulb, but I'd assume it'd be bright as the fires of hell. Unless you've got 10 40-watt bulbs or 4 100-watt bulbs running, I'd assume it's 40 watts, not 400.
 
iamwiz82

iamwiz82

Lifer
Jan 10, 2001
30,772
13
81
I bet you live in Cali with those kind of electricity prices.

EDIT: HA, I was right!
 
S

Savij

Diamond Member
Nov 12, 2001
4,233
0
71
Originally posted by: RIGorous1I'm paying $175.2 every year on energy to keep this bulb on at night for 1 year ?
Click to expand...

No, you're paying 175.2 to light up your porch with more lights than you need, 24 hours a day, 182.5 days a year
 
R

RIGorous1

Platinum Member
Oct 26, 2002
2,053
0
71
so is anyone gonna confirm my math? I am not sure that 400 watts running for 1 hour = 400 watt-hours... Does this sound right?

PS. I was thinking of having 40 watt bulbs x 10 or using one large High Pressure Sodium 400 watt bulb.
 
S

Savij

Diamond Member
Nov 12, 2001
4,233
0
71
Originally posted by: RIGorous1
so is anyone gonna confirm my math? I am not sure that 400 watts running for 1 hour = 400 watt-hours... Does this sound right?

PS. I was thinking of having 40 watt bulbs x 10 or using one large High Pressure Sodium 400 watt bulb.
Click to expand...

Your math looks ok, but why you need 400 watts for a porch you aren't even using seems crazy...cut it down to 40 or 60 watts...even that might be overkill for lighting up a place that you're not using...and why is it on 12 hours a day instead of just when it's dark outside
 
K

kponds

Senior member
Dec 10, 2000
265
0
0
Your math is correct. 400 watts running for an hours is 400 watt hours and at the $.10 per kwh rate you specified would cost you $.04 per hour that the lights are running.

The comment about the lighting being very bright is correct - or either you have a very big porch. If the porch is properly lit (not to bright) keep in mind the following:

Compact Flourescent Lamps: cost about 25% of the cost of regular incandescent lamps to operate. To get the same light level, you'll need about 100 watts of Flourescent. Your electric bill would be 1/4 of the $17?.?? you calculated or about $47/year if they ran the same amount of time.

I suspect you have a whole lot more light than you really need. replace the lamp (if its a normal incandescent with a 60 or 100 watt lamp and see if you have enough light - I suspect you will. If that works, consider replacing it with a 15 to 25W compact flourescent.
 
A

arcas

Platinum Member
Apr 10, 2001
2,155
2
0
If you have 400 watts on your porch, I assume you live out in the country. If so, you might want to make sure you're only illuminating your porch area and not needlessly trying to illuminate the night sky. Also, it would probably be worth it to look into low pressure sodium lamps as they're far more efficient than either incandescent or fluorescents. It's also more friendly to astronomers in the area since filters exist which do a good job of blocking out light pollution from low pressure sodium lights.

 
TuxDave

TuxDave

Lifer
Oct 8, 2002
10,571
3
71
Sounds about right. Divide that number by 12 because that's how much extra you'll see on your monthly bill.
 
MrDudeMan

MrDudeMan

Lifer
Jan 15, 2001
15,069
94
91
400w = 4x too much power (giving you good odds, it is really about 6.6x too much)

your math is correct. downgrade your lightbulbs...which leads me to my next point: dont smoke crack.
 
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