The most critical factors in determining whether installing wind turbines is financially worthwhile are the initial cost of the installation and the annual energy production. In determining economic feasibility, wind energy must compete with the energy available from competing technologies. If a system produces electrical energy for a grid, the price for which the electrical energy can be sold is also critical. Wind farms today are competitive with all new power plants, except for combined-cycle natural gas turbines because the price for natural gas has declined from peak values due to the exploitation of shale formations. Oil prices were around $60/bbl in 2018. As natural gas replaces coal for producing electricity and as electric vehicles increase substantially, some predict a decline in oil demand and that even some oil reserves will be stranded. To increase market penetration of wind systems, the return from the energy generated must exceed all costs in a reasonable time.