thats not correct a killowat is 1000 watts... so it would really be:
.6 * 12 * 30 = 216 kilowat hours
Here where i live (top secret underground texas fortress of doom)
its like $0.10 per kwh... so id pay about $22 extra a month plus taxes and stuff for a 600watter...
Not to mention the extra A/C needed to keep the fortress cool in the summer with that 600w light blaring.
Imagination is more important than knowledge.