Example:
15 Btu (th) = 9.871103e+22 eV
1 Btu (th) = 6.580735e+21 eV | 1 eV = 1.519587e-22 Btu (th)
Conversion Steps:
15 × (1054.349999974 / 1.602177e-19) = 9.871103e+22