Buying it right the first time

You could try a Coralife Aqualight power compact fixture. You can get them for a 20 inch aquarium and the should provide the light you need. They will also fit your budget.

 

first I would say if you want something about that size try looking into your local reef club and buy used equipment it saves a lot of money than buying new stuff. I bought several stuff including my lights that I am using now from a local reefer. If not you can try looking into buying off someone in a forum willing to sell. I think you would probably be alright with the 24" there will be some hang off though. Like another person said go for the viper.

 

I've said this before and will say it again. A watt is a watt. If you have 150w of MH and 150w of T5 they will use about the same amount of electricity. Now, MHs are not as efficient as T5s. So a 250w MH pendant may use about 280w of electricity with an average ballast, while 250w of T5 may use about 265. However, this really depends on the ballast, a good electronic ballast will go a lone way to helping efficiency. IMO, the idea that MHs are "energy hogs" is from the old magnetic ballasts which were much less efficient and that people usually have more watts of Mh lighting. For example, Somebody may have a 324w T5 fixture and compare it to a 2x250w MH setup, obviously there will be a large difference in energy consumption.

 

If you want to know how much you will be spending on lighting your tank, you have to look at how your being billed for your electric consumption. In Florida(and I think pretty much everywhere else) utilities bill you by kilowatt hour. This is just the way they meter usage. A kilowatt hour is the equivelant of 1000 watts being consumed over the period of one hour. For instance, if your running 2 X 250 MH, then your total system power is rated at 500 watts. As the previous post states, this will be slightly off based on your ballasts, but it will be close. So if your running this setup for 6 hours a day, then your using 3 kilowatt hours per day. Use this formula... Total monthly KWh usage = (your systems wattage / 1000) * total hours run per day * 30 (days in month). For our example this would be (500/1000)*6*30 which equals 90 kilowatt hours per month. Then check your electric bill, it will tell you how much you're being charged per KWh. Then multiply your usage times that rate and you'll have a close estimate. Some utilites also have a fuel charge, so this will have to be factored in to get a better estimate. I always add 10% to account for inefficiency, but that's just me. You can use this same method for all your aquarium equipment that either runs constantly or for set time periods. I hope this is helpfull, and if there are any electricians out there who can add any parts I misssed, please do.

 

How did you know I would like the math challenge.
It should cost me @ .12 cents per KWhH, $4.32 to run a 150 watt 8 hours a day 30 days a month.

Thanks