At the moment I run a 600w hps was thinking of getting a 300w t5 light. Does this mean I would cut my electric bill in half? or does a 300w clf light mean it give 300w of light but only use's 50w to power it?
I would not say pitiful, a friend of mine who has been growing for 30 years gets a pound of one plant using T-8 and T-12 bulbs. He is currently upgrading to T-5's and expects to increase yield by 10-15%.
I had 600w of CFLs, and upgraded to 600w HPS within 9 days as the CFLs just didn't compare watt for watt with HPS - 300w bulb is approx 15,000 lumens, 600w HPS is approximately 90,000 lumens - stick with what you have