The nearest expiration date for ERCOT South 345 kV Hub 5 MW Off-Peak Futures (Aug 2016) is Jul 29, 2016.
The best time to sell a futures contract is when you've already made money on the investment, but still have plenty of time left before the expiration date. Thus, a good option would be to sell ERCOT South 345 kV Hub 5 MW Off-Peak Futures (Aug 2016) before Jul 29, 2016.