t5 vs pc lighting

[redbellyPirahna4]

i was thinking about buying this http://www.aquatraders.com/ProductDetails.asp?ProductCode=51206 72" 384W Power Compact to use for my 210 because all i have on it right now is just 2 glo t5 ho 36" so its only around 80watts altogether. my question is how much more electricy will the power compacts used compare to t5's because with all my tanks running the electricity bill is about $50-70 more or something like that not sure exactly.
so which is more engergy efficient t5's or pc's but i also have a 250watt metal halide somewhere that i could use but i know that it would take more to power it

 

[Clay]

You gave your own answer:
384w - 80w = 304w
.304 x cost of kwh in your area = additional cost per hour.
Additional cost per hour x number of hours lights are on = additional cost per day
Additional cost per day x 30 = additional cost per month.

This is how you can figure out how much a lighting upgrade will cost you in electricity.

Next is to ask why you're changing light. Do you find that you don't have enough light? Are you trying to grow plants? What would a MH do for you?