Quote:
Originally Posted by atreis
Obviously, only during the winter, but ...
This one is a wash: You have the heat the tank somehow - whether you heat with MH or a heater, it's still electric. It would reduce the effective energy consumption of the MH, but not of the overall system.
e.g. Let's assume for a minute that heating with MH is 25% efficient - in other words, 25% of the electricity going into the MH bulbs is actually converted to heat within the tank. (BTW, I've absolutely no clue what the real number here might be). That means that if you have 500W of MH, 125W of that displaces 125W of electricity needed for operating a heater.
Given the above, if you go with 200W of LED (and let's assume they put 0% of their energy into heat in the tank - another completely fabricated number but it makes life easy), or 500W of MH, and let's assume there's a 300W heater, and that if there is no heat provided by the lighting it will operate for 3 hours a day (another fabricated number):
MH:
500W for 8 hours = 4kWH (light)
lighting puts 1000WH (8*125W) of heat into the tank - no need for heater
Total: 4kWH
LED:
200W for 8 hours = 1.6kWH (light)
300W for 3 hours = .9kWH (heat)
Total: 2.5kWH
Let's assume for grins that one uses a 700W chiller and it's able to remove 500W of energy per hour, and that without any light consideration it would normally operate for 3 hours a day during the summer to remove ambient heat. (Another set of completed fabricated numbers. We'll leave out the household AC to keep things simple, but obviously that would just increase the energy needs, where applicable.)
MH:
500W for 8 hours = 4kWH (light)
700W for 3 hours = 2.1kWH (ambient cooling)
700W for 2 hours = 1.4kWH (1000WH of heat added by lights)
Total: 7.5kWH
LED:
200W for 8 hours = 1.6kWH (light)
700W for 3 hours = 2.1kWH (ambient cooling)
Total: 3.7kWH
Spring and fall would fall somewhere in between. Plug in your own numbers and fiddle at will... Things I suspect everyone would agree on: less lighting wattage is needed for LEDs than MH, and substantially less heat is added to the water by LEDs than MH.
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What? You literally just made up numbers and a scenario, and came to a conclusion. Additionally, you have underestimated the heater wattage and overestimated the chiller wattage. A 700w (1hp) chiller is rated for 250-700g depending on manufacturer, but a 300w heater is only rated for 50-150 gallons. Your scenario is completely unrealistic to skew the numbers in your favor. I know you probably didn't do it on purpose, but
this is exactly the point I am trying to make. People underestimate heating and overestimate cooling.
Here's my scenario:
500w of MH and a heater not running during the day - compared to 200w of LED and 500w of heating running intermittently throughout the day.
It's pretty simple and this will be my last post on the subject. But it's just not fair to only cast the heat generating of MH as a negative, when the average person runs more wattage of heating on their tank than cooling anyway, and really could use that extra heat for half the year.