The payback probabilistic analysis shows that the investment will be most probably returned in 6 years (72 months). The payback period can be as high as 14 years (90% confidence), for the personal sector. However, if the social costs and benefits are included in the calculation, the maximum return period could decrease to 12.8 years (154 months). In addition, the addition of social benefits reduces the most probable payback return period to 5.7 years (68 months).