Posted by *captain bob* on July 18, 2004, 9:46 pm

I was just trying to figure out what the additional cost to run an AC

is to cool a room with a Compact flurescent bulb than an incandescent

light bulb

the 75 watt equivalent CF bulb uses 18 watts

how much of this is heat and how much is light?

17:1?

16:2?

assuming there is 2 watts of light, then the cf bulb is making 16

watts of heat and a standard incandescent makes 73 ( 75-2 )

this is a difference of 57 watts

I read that a btu = 3.41214 watts of heat.

since the AC has an EER of 10.7 (btus per watt to run the AC)

then it moves 3.14 watts of heat with 1 watt of power for the AC?

this is more effecient than I expected.

so the standard bulb uses 57 watts more, plus another 18 for the AC to

move the heat.

is this right? or where have I gone wrong?

thanks

Posted by *captain bob* on July 18, 2004, 9:49 pm

*>I was just trying to figure out what the additional cost to run an AC*

*>is to cool a room with a Compact flurescent bulb than an incandescent*

*>light bulb*

oops I mean the additional cost for incandescent over CFL

Posted by *danny burstein* on July 18, 2004, 9:59 pm

*>I was just trying to figure out what the additional cost to run an AC*

*>is to cool a room with a Compact flurescent bulb than an incandescent*

*>light bulb*

*>the 75 watt equivalent CF bulb uses 18 watts*

*>how much of this is heat and how much is light?*

*>17:1?*

*>16:2?*

except for the amount of light going out the window, every single watt

being used up by the lamp, whether as "light" or as "heat", eventually

turns to heat inside teh room.

*>assuming there is 2 watts of light, then the cf bulb is making 16*

*>watts of heat and a standard incandescent makes 73 ( 75-2 )*

*>this is a difference of 57 watts*

nope. it's 18 watts versus 75 watts. again, it doesn't matter what the

watts get used for in the room. it can be for light, it can run a fan,

operate a tv, run a refrigerator. It all turns to heat.

*>I read that a btu = 3.41214 watts of heat.*

*>since the AC has an EER of 10.7 (btus per watt to run the AC)*

*>then it moves 3.14 watts of heat with 1 watt of power for the AC?*

eyup. that's why, an air conditioner in "heat pump" mode is more efficient

than straight electric heat, and often better than a gas or oil furnace.

*>this is more effecient than I expected.*

*>so the standard bulb uses 57 watts more, plus another 18 for the AC to*

*>move the heat.*

eyup, again, except for the bit of calculating in ALL the wattage.

*>is this right? or where have I gone wrong? thanks*

You're pretty much right except for that sidetrack...

--

_____________________________________________________

Knowledge may be power, but communications is the key

dannyb@panix.com

[to foil spammers, my address has been double rot-13 encoded]

Posted by *captain bob* on July 18, 2004, 10:15 pm

On Sun, 18 Jul 2004 21:59:33 +0000 (UTC), danny burstein

*>>I was just trying to figure out what the additional cost to run an AC*

*>>is to cool a room with a Compact flurescent bulb than an incandescent*

*>>light bulb*

*>>the 75 watt equivalent CF bulb uses 18 watts*

*>>how much of this is heat and how much is light?*

*>>17:1?*

*>>16:2?*

*>except for the amount of light going out the window, every single watt *

*>being used up by the lamp, whether as "light" or as "heat", eventually *

*>turns to heat inside teh room.*

*>>assuming there is 2 watts of light, then the cf bulb is making 16*

*>>watts of heat and a standard incandescent makes 73 ( 75-2 )*

*>>this is a difference of 57 watts*

*>nope. it's 18 watts versus 75 watts. again, it doesn't matter what the *

*>watts get used for in the room. it can be for light, it can run a fan, *

*>operate a tv, run a refrigerator. It all turns to heat.*

*>>I read that a btu = 3.41214 watts of heat.*

*>>since the AC has an EER of 10.7 (btus per watt to run the AC)*

*>>then it moves 3.14 watts of heat with 1 watt of power for the AC?*

*>eyup. that's why, an air conditioner in "heat pump" mode is more efficient *

*>than straight electric heat, and often better than a gas or oil furnace.*

*>>this is more effecient than I expected.*

*>>so the standard bulb uses 57 watts more, plus another 18 for the AC to*

*>>move the heat.*

*>eyup, again, except for the bit of calculating in ALL the wattage.*

*>>is this right? or where have I gone wrong? thanks*

*>You're pretty much right except for that sidetrack...*

ok thanks, I forgot about that

the light is reflected and absorbed by everything in the room until it

all turns to heat

the difference between 75 and 18 is still 57, so my calculations are

the same

does anyone know how efficient a household light bulb is? 1%? 2%?

I know the higher wattage ones are better

if memory serves one 100 watt bulb produces more than twice the light

of 2 60s

with the price of CFLs dropping (.50 per 18 watt bulb) they are

becoming a better deal

thanks

Posted by *nicksanspam* on July 19, 2004, 12:29 am

*>I read that a btu = 3.41214 watts of heat.*

No. Btus are energy. Watts are power. Please learn the difference.

*>...the AC has an EER of 10.7 (btus per watt to run the AC)*

No... 10.7 = Btu/Wh, in these bastardized units. If it moves

10.7 Btu/h with 3.41 Btu/h of electrical power, the COP is 3.14.

*>then it moves 3.14 watts of heat with 1 watt of power for the AC?*

Yes. Removing 18 watts of heat requires 18/3.14 = 5.7 W of electrical power.

Nick

>I was just trying to figure out what the additional cost to run an AC>is to cool a room with a Compact flurescent bulb than an incandescent>light bulb