Optimal tilt angle of PV array is when the system generates maximum amount of electricity. Such optimum tilt angle for Jerusalem is 25 degrees. This optimum is from the energy point of view.
PV array supplies electricity to energy consumer or to electric utility grid. In case when the related electricity tariffs are according to peak demand, the cost of electricity in peak hours is much higher than in off-peak hours. Therefore it may be expected that the yearly optimum tilt angle from the economic point of view will be declined towards months and hours with the highest electricity tariffs. This would result in lower economic optimum tilt angle than from the energy point of view (25 deg).
The analysis of energy generation and energy cost according to peak demand tariffs shows that for unlimited area available for PV array, the optimum tilt angle from economic point of view is similar to the optimum from the energy point of view (25 deg). This happens because of low sensitivity of energy generation in tilt angle range 0-25 deg in summer, comparing to very high sensitivity in winter, which means that the economic benefit from increasing tilt angle in January is higher than from decreasing the tilt angle in July in range 0-25 deg. Optimum tilt angle for January in Jerusalem is 52 deg.
This work contains large volume of useful data and may be helpful for other works related to solar energy.