March 2, 2016 DG-3: To calculate the number of RECs from a 10 kW system, you use the following formula: 0.010MW x 14.38 % x 8760 hours x 5 years = about 63 RECs. What does the 8760 represent? 8,760 is number of hours in a year: 24 hours/day x 365 days/year.