I just looked into the economics of rotor sails. On average, they save $400/day ($146,000/year) in fuel costs (2017) or about ~10% of fuel consumption. In real

I just looked into the economics of rotor sails. On average, they save $400/day ($146,000/year) in fuel costs (2017) or about ~10% of fuel consumption. In real terms, it's not much. They cost about €1-2 mil ($1.1-2.3). Under the most ideal circumstances, that is a ~8 year payback, which is fairly long. In order for the economics to work out, oil prices need to be higher and externalities (CO2 emissions) need to be included in the price.