ok i wanted to upgrade to a 600 watt hps and seeing most are switchable between 120 or 240 which voltage is better to use a friend of mine said running it on 240 is cheaper than running it on 120 but i can't see how seeing its pulling the same amount of power
Your friend is uneducated regarding electricity. 120v and 240v use the same amount of power. The only difference is the amperage being drawn is lower with 240v. It's still a 600w fixture regardless of the voltage used.
I always view it as a watt is a watt. W=Volts*Amps so no matter how many volts you run, the same amount of wattage is consumed. The only change is amperage. This can be beneficial depending on your home wiring. if you have space for an extra double throw breaker then I would go ahead and add the 220 circuit. Less amp now mean you have more headroom in the event of advancement. Also, you can run three conductor grounded, use the white as neutral and split the 220 and run your 120 appliances off each 120 leg of the 220 circuit. Make sure to use the ground wire though as the ground(for clarity). Sorry if that was too much info. Or not enough in some areas. Oh yeah, make sure to match wire size to amp draw, and give urself some headroom on the main home run. If you can put everything on its own circuit(the 220 added), it will save you headache and heartache.
thanks after this harvest another 5 weeks i was gonna rehab my room i need breakers anyhow so when the electrition put in the new panels i was gonna have him run a 240 plug to my growroom for the new light and a good thing is i found a electrition that will work for bud woohoo so saves me some cake that i can spend at the hydro store