The heat loss through a window (R-2) is 10 MMBTU/year. Calculate the payback period (in years) ifArgon is filled in the window to increase the effective R-value of the window to 7. Assume heating price to be $10/MMBTU and the cost for filling Argon is $20.Heat lost through new window per year = (10 x 2) / 7 = 2.84 MMBTUs/yrReduction in heat lost per year = 10 - 2.84 = 7.16 MMBTUs/yrSavings in energy cost per year = 7.16 x 10 = $71.6Payback period = 20 / 71.6 = 0.28 yrs

0.28 year

Explanation:

Heat lost through new window per year = heat loss through a window / R- value = (10 MMBTU/year × 2) / 7 = 2.86 MMBTUs/yr

Reduction in heat lost per year = heat loss through a window - Heat lost through new window per year = 10 MMBTUs/yr - 2.86 MMBTUs/yr  = 7.14 MMBTUs/yr

Savings in energy cost per year = Reduction in heat lost per year × heating price = 7.14 MMBTUs/yr × $10/MMBTU = $71.4 / yr

Payback period =  cost for filling Argon / Savings in energy cost per year = $20 / $71.4 /yr =  0.28 yrs

electrical to thermal