Your 600w MH uses more than 600w because that's just the bulb. Tack another 10% on for the ballast. So more like 660w but the best way would be to check it with a kill-a-watt meter.
As far as final cost, it depends what your power co charges per Kw/h. It varies greatly depending on where you live.
Average Revenue per Kilowatthour by State
(Lowest to Highest Rate as of September 2006)
[TABLE="align: center"]
[TR]
[TD="width: 40, align: center"]
Rank[/TD]
[TD="width: 160, align: center"]
State[/TD]
[TD="width: 200, align: center"]
Average Electricity Rate for
All Sectors
(Cents per Kilowatthour)[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
1[/TD]
[TD="width: 150, align: left"]
Idaho[/TD]
[TD="width: 110, align: right"]
4.70[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
2[/TD]
[TD="width: 150, align: left"]
West Virginia[/TD]
[TD="width: 110, align: right"]
5.12[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
3[/TD]
[TD="width: 150, align: left"]
Wyoming[/TD]
[TD="width: 110, align: right"]
5.37[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
4[/TD]
[TD="width: 150, align: left"]
Kentucky[/TD]
[TD="width: 110, align: right"]
5.56[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
5[/TD]
[TD="width: 150, align: left"]
Washington[/TD]
[TD="width: 110, align: right"]
6.04[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
6[/TD]
[TD="width: 150, align: left"]
Utah[/TD]
[TD="width: 110, align: right"]
6.32[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
7[/TD]
[TD="width: 150, align: left"]
Oregon[/TD]
[TD="width: 110, align: right"]
6.43[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
8[/TD]
[TD="width: 150, align: left"]
Indiana[/TD]
[TD="width: 110, align: right"]
6.46[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
9[/TD]
[TD="width: 150, align: left"]
Missouri[/TD]
[TD="width: 110, align: right"]
6.52[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
10[/TD]
[TD="width: 150, align: left"]
North Dakota[/TD]
[TD="width: 110, align: right"]
6.63[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
11[/TD]
[TD="width: 150, align: left"]
Nebraska[/TD]
[TD="width: 110, align: right"]
6.72[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
12[/TD]
[TD="width: 150, align: left"]
Minnesota[/TD]
[TD="width: 110, align: right"]
6.81[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
13[/TD]
[TD="width: 150, align: left"]
Virginia[/TD]
[TD="width: 110, align: right"]
6.94[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
14[/TD]
[TD="width: 150, align: left"]
South Dakota[/TD]
[TD="width: 110, align: right"]
7.00[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
15[/TD]
[TD="width: 150, align: left"]
Montana[/TD]
[TD="width: 110, align: right"]
7.07[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
16[/TD]
[TD="width: 150, align: left"]
Tennessee[/TD]
[TD="width: 110, align: right"]
7.23[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
17[/TD]
[TD="width: 150, align: left"]
South Carolina[/TD]
[TD="width: 110, align: right"]
7.28[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
18[/TD]
[TD="width: 150, align: left"]
Alabama[/TD]
[TD="width: 110, align: right"]
7.39[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
19[/TD]
[TD="width: 150, align: left"]
Kansas[/TD]
[TD="width: 110, align: right"]
7.44[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
20[/TD]
[TD="width: 150, align: left"]
Illinois[/TD]
[TD="width: 110, align: right"]
7.50[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
21[/TD]
[TD="width: 150, align: left"]
Iowa[/TD]
[TD="width: 110, align: right"]
7.51[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
22[/TD]
[TD="width: 150, align: left"]
New Mexico[/TD]
[TD="width: 110, align: right"]
7.56[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
23[/TD]
[TD="width: 150, align: left"]
Colorado[/TD]
[TD="width: 110, align: right"]
7.62[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
24[/TD]
[TD="width: 150, align: left"]
Arkansas[/TD]
[TD="width: 110, align: right"]
7.64[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
25[/TD]
[TD="width: 150, align: left"]
Ohio[/TD]
[TD="width: 110, align: right"]
7.77[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
26[/TD]
[TD="width: 150, align: left"]
Georgia[/TD]
[TD="width: 110, align: right"]
7.78[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
27[/TD]
[TD="width: 150, align: left"]
North Carolina[/TD]
[TD="width: 110, align: right"]
7.91[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
28[/TD]
[TD="width: 150, align: left"]
Oklahoma[/TD]
[TD="width: 110, align: right"]
8.01[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
29[/TD]
[TD="width: 150, align: left"]
Mississippi[/TD]
[TD="width: 110, align: right"]
8.24[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
30[/TD]
[TD="width: 150, align: left"]
Michigan[/TD]
[TD="width: 110, align: right"]
8.25[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
31[/TD]
[TD="width: 150, align: left"]
Wisconsin[/TD]
[TD="width: 110, align: right"]
8.32[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
32[/TD]
[TD="width: 150, align: left"]
Pennsylvania[/TD]
[TD="width: 110, align: right"]
8.63[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
33[/TD]
[TD="width: 150, align: left"]
Arizona[/TD]
[TD="width: 110, align: right"]
8.79[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
34[/TD]
[TD="width: 150, align: left"]
Louisiana[/TD]
[TD="width: 110, align: right"]
8.80[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"] [/TD]
[TD="width: 150, align: left"]
National Average[/TD]
[TD="width: 110, align: right"]
9.26[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
35[/TD]
[TD="width: 150, align: left"]
Nevada[/TD]
[TD="width: 110, align: right"]
10.07[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
36[/TD]
[TD="width: 150, align: left"]
Florida[/TD]
[TD="width: 110, align: right"]
10.49[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
37[/TD]
[TD="width: 150, align: left"]
Delaware[/TD]
[TD="width: 110, align: right"]
10.66[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
38[/TD]
[TD="width: 150, align: left"]
Texas[/TD]
[TD="width: 110, align: right"]
10.75[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
39[/TD]
[TD="width: 150, align: left"]
Maryland[/TD]
[TD="width: 110, align: right"]
11.10[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
40[/TD]
[TD="width: 150, align: left"]
District of Columbia[/TD]
[TD="width: 110, align: right"]
11.34[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
41[/TD]
[TD="width: 150, align: left"]
Vermont[/TD]
[TD="width: 110, align: right"]
11.54[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
42[/TD]
[TD="width: 150, align: left"]
Maine[/TD]
[TD="width: 110, align: right"]
11.88[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
43[/TD]
[TD="width: 150, align: left"]
New Jersey[/TD]
[TD="width: 110, align: right"]
12.77[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
44[/TD]
[TD="width: 150, align: left"]
Alaska[/TD]
[TD="width: 110, align: right"]
12.82[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
45[/TD]
[TD="width: 150, align: left"]
New Hampshire[/TD]
[TD="width: 110, align: right"]
13.62[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
46[/TD]
[TD="width: 150, align: left"]
California[/TD]
[TD="width: 110, align: right"]
13.90[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
47[/TD]
[TD="width: 150, align: left"]
Rhode Island[/TD]
[TD="width: 110, align: right"]
14.06[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
48[/TD]
[TD="width: 150, align: left"]
New York[/TD]
[TD="width: 110, align: right"]
14.89[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
49[/TD]
[TD="width: 150, align: left"]
Massachusetts[/TD]
[TD="width: 110, align: right"]
15.71[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
50[/TD]
[TD="width: 150, align: left"]
Connecticut[/TD]
[TD="width: 110, align: right"]
15.74[/TD]
[/TR]
[TR]
[TD="width: 40, align: center"]
51[/TD]
[TD="width: 150, align: left"]
Hawaii[/TD]
[TD="width: 110, align: right"]
21.51[/TD]
[/TR]
[/TABLE]