Im in the Uk....i think im charged 0.31p per KWH....so if im running my lamp 12 hours a day its costing me about £3 a day.Not sure how much you get charged per kWh but you would probably be better off running the hps all the time. 100 watts isn't really saving a lot and you could make up that difference in electricity by switching all the bulbs in your house to energy saving bulbs and turning the water heater down a bit. Use this calculator to determine what the difference is in cost, even at 15 cents per kWh the difference is only $10 a month. Don't get a smaller setup, if anything make the most of what you got. If you only have one female use super cropping to make it a big bush and get more bud.
http://www.electricity-usage.com/Electricity-Usage-Calculator.aspx
The bulbs that im using on the plant in between the HPS are low voltage energy saving bulbs....they give off 100w light but only use 18w electricity. They seem to be doing the job
Ive got 2 other plants on the go so if this one turns out to be a male then il have another couple of chances
