I went and did a further measurement to check my original figures, and did in fact read my amp meter incorrectly.
The electric cost should be 1 X 240 = 240 watts x 12 hours daily running time = 2880 watthours X 365/12/1000 = 8.760Kwh X $0.1/Kwh = $8.76
Total cost = 8.76 + 4.6 + 7.5 = $20.86
This seems to compare with what I calculated previously 2 years ago.
Sorry about the error.
Pat
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