My tank is a Perfecto 5' 120. Given the truly effective coverage of AI Sol LEDs being about 24"X24", I would need 4 units over my tank due to the center brace. Dapple has a standard 6' 125 which has 2 center braces. Ironically, I would need 1 more unit than he needs to light my tank. That alone disproves the "LED is cheaper" theory. I have already proven that my tank is sufficiently lit with two 250 watt 20,000k bulbs. I'll supply the math to support my statement.
As of 12/1/2012 the electricity rates for Knoxville Utilities Board customers was 9.432 cents per kWh.
Assume the lights are on for 10 hours each day, 365 days per year.
A kWh is 1000 watts for a time period of 1 hr.
2X250 watt bulbs = 500 watts per hour
500 watts for 10 hours is 5000 watts, or 5 kWh.
5 kWh @ $.09432 = $.4716 per day, or $172.13 per year. That's $14.34 per month on your bill.
Assuming you replace the bulbs every 9 months, that's $26.66 (Two Plusrite brand 20,000k 250 watt single ended bulbs at $13.33 each)
Over a 10 year period (that seems to be the consensus on how long LEDs last) I will change bulbs 13.33 times, for a grand total of $355.38.
Power consumption over a 10 year period will be $1721.30.
$1721.30 + $355.38 = $2076.68
For the AI Sol LEDs:
4X75 watts = 300 watts per hour.
300 watts @ 10 hours = 3000 watts per day, or 3 kWh.
3 kWh @ $.09432 = $.28296 per day, or $103.28 per year. That's $8.61 on your monthly bill.
4 AI Sol units @ $400 each, plus $70 for the controller = $1670
Power consumption over a 10 year period is $1032.80
$1032.80 + $1670 = $2702.80
LEDs would cost me an additional $626.12 over a 10 year period.