11.4 / 100 (pounds) / 1000 (watts) * 24 (days) * 365.25 (years)
= £ 1.00 / Watt / year
10p/kWh is £0.88/Watt/year
p/kWh pounds/W/year 13 1.14 14 1.23 15 1.31 16 1.40 17 1.49 18 1.58 19 1.67 20 1.75 25 2.19 30 2.63 35 3.07 40 3.51 45 3.94 50 4.38 55 4.82 60 5.26 65 5.70 70 6.14 75 6.57 80 7.01 85 7.45 90 7.89 95 8.33 100! 8.77