# Why do incandescent lights suck?

# The Math

Quote:As an example:

Forty 100-watt incandescent lamps (4,000w = 68,000 lumens) require 12,283 Btu of cooling (slightly over one ton). The same site could use 27 four-lamp fluorescent fixtures (or about 4,000 watts = 240,000 lumens) at the same one ton of cooling load, yet produce 172,000 more lumens.

(Please see: Related Efficiency Upgrades – Lighting for more information on this.)

Fluorescents produce more light per watt used then any incandescent can ever do. HID (HPS in particular) produce WAY more light for every watt used. Let’s do some math:

150w incandescent = 2,550 lumens or 17 lumens per watt

150w halogen = 3000 lumens or 20 lumens per watt

150w of Fluorescents = 9,000 lumens or 60 lumens per watt

150w of Compact Fluorescents = 10,500 lumens or 70 lumens per watt

150w Metal Halide = 13,500 lumens or 90 lumens per watt

150w High Pressure Sodium = 16,000 lumens or 107 lumens per watt

Now since you’re paying for each watt used wouldn’t you want that watt to put out as much light as it could? Using an incandescent bulb you are going to pay way more in electric costs then you would if you used a HID because you’ll need more watts for the grow to come out good. To produce killer bud you will need about 7,000 lumens per sq ft in your grow room. So, in a 5sq ft grow room you would need 35,000 total lumens (7,000 * 5 = 35,000) to reach the optimum 7,000 lumens per sq ft. To get 35,000 lumens you would need:

13.7 – 150w incandescent or 2,058 watts = 35,000 lumens

11.6 – 150w Halogens or 1750 watts = 35,000 lumens

3.8 – 150w Fluorescents or 583 watts = 35,000 lumens

3.3 – 150w Compact Fluorescents or 500 watts = 35,000 lumens

2.5 – 150w Metal Halide or 389 watts = 35,000 lumens

2.1 – 150w HPS or 327w = 35,000 lumens

Now according to our Grow Guide (lighting section):

Quote:To determine the cost of operating your light:

Find your KWH charge on your electric bill. Assume you have a 1000 watt light and your KWH charge is $.05/hour. A kilowatt equals 1000 watts, therefore it will cost you .05 cents per hour to run that light. Here’s another example. Say you have a 400 watt light and your KWH charge is $.03. Since 400 watts is not a kilowatt, you must divide 400 by 1000 = .4 kilowatts x .03 (KWH rate from electric bill) = $0.012 cents per hour to run.

So, let’s use me as an example, I pay $0.08 per KWH. Using our 5 sq ft grow room example above and shooting for 7,000 lumens per sq foot:

## Incandescent lights

2,058w = $0.16 an Hr (2.058*0.08=0.16464) or $3.84 a day (0.16*24=3.84) or 115.20 a month (3.84*30=115.20) or 1,382.40 a year (115.20*12=1382.40)

## Halogen lights

1750w = $0.14 an Hr or $3.36 a day or $100.80 a month or $1,209.60 a year.

## Fluorescent lights

583w = $0.05 an Hr or $1.20 a day or $36 a month or $432.00 a year.

## Compact Fluorescents

500w = $0.04 an Hr or $.96 a day or $28.80 a month or $345.60 a year.

## Metal Halide

389w = $0.03 an Hr or $.72 a day or $21.60 a month or $259.20 a year.

## High Pressure Sodium

327w = $0.03 an Hr or $.72 a day or $21.60 a month or $259.20 a year.

As you can see it adds up real quick. In one month of 24hr light I would spend $93.60 more to run incandescent lighting than I would for a HPS and in a year it would cost me $1,382.40 to run those same incandescent lights 24 hrs a day when it would only cost me $259.20 to run the HPS. That’s $1,123.20 more it would cost me per year to run an inferior light. Not to mention how much more it would cost to cool that same 5sq ft grow space running incandescent light over HPS.

So, as you can plainly see even if the light spectrum was correct and heat wasn’t a problem it would cost you WAY more to run incandescent/halogen lights than it would to run a HID. The money you save in just one month would almost pay for the HPS. When you break it down to cost per watt doesn’t it make more sense to buy the HID in the first place?

Any questions?

*Incandescent lights*.. **More costly** then we all thought.