leave them at high voltage if you can.....240 volts will pull less amps(current, electrical flow) than 120 volts. you pay for current (flow) not voltage. according to Ohm's law, current equals voltage divided by resistance. 240 volts has a higher potential, it uses 1/2 the amperes (current flow) than wiring it for 120 volts. to get 240 volts you tie two breakers together on your panel so that both legs have 120 volts as opposed to 120 having a hot and a neutral. when i hit the lottery i'm going to travel the country wiring up grow rooms for heads!