Modern wind turbines fall into two basic groups: the horizontal-axis variety and the vertical-axis design (the eggbeater-style or Darrieus model). Horizontal-axis wind turbines typically either have two or three blades. These three-bladed wind turbines are operated "upwind," with the blades facing into the wind. Wind turbines can be built on land or offshore in large bodies of water like oceans and lakes.
Utility-scale turbines range in size from 100 kilowatts to as large as several megawatts. Larger wind turbines are more cost effective and are grouped together into wind farms, which provide bulk power to the electrical grid. In recent years, there has been an increase in large offshore wind installations in order to harness the huge potential that wind energy offers off the coasts of many maritime countries.
Single small turbines, below 100 kilowatts, are used for homes, telecommunications dishes, or water pumping. Small turbines are sometimes used in connection with diesel generators, batteries, and solar photovoltaic systems. These systems are called hybrid wind systems and are typically used in remote, off-grid locations, where a connection to the utility grid is not available.
Wind produced electricity at the level of a utility is usually a "distributed" source with the turbines relatively close to the end users. These large sources are called wind farms. The major exception to a distributed network of wind turbines is in offshore locations. Although the offshore locations are more expensive to install than onshore wind turbines, the wind tends to be more constant over the water. Off shore locations are so expensive that in most cases, the installations are subsidized by offering a added payment to the use rate. In Germany, which is aiming at providing electricity primarily from solar, wind, and water, the price of electricity is very high (about $0.40/kwhr). For offshore wind, contracts are let on the basis of the existing rate plus a subsidy of approximately and extra $0.06/kwhr. This year (2017), however, the bids for subsidy were quite low, so the potential is that offshore wind can compete at market rates in the near future - as long as the base rate is high enough - at least in the range of $0.40/kwhr - a rate that is would be unacceptably high in North America.
As with solar power, wind power is cheapest when it does not have to deliver power 24 hours a day. The reason for the less expensive power is that no backup or storage is needed if power can be sold as it is collected. On average wind turbines can deliver power about 40% of the time. In Germany the backup is brown coal, so the net result is a very carbon intensive electricity supply.
By contrast, onshore wind is relatively inexpensive to install and as long as the power is non-despatchable (can be sold when it is collected), the price to the customer is quite low, sometimes as low as in the range of $0.070/kwh. If the power needs to be delivered as despatchable power (must be on demand supply 24 hours a day), then the cost rises rapidly. The 60% of the time the wind is not adequate must be supplied from a backup system. If the backup is to be powered by the wind, then the wind farm must be at least 2.5 times as big as the stated capacity, and some means of storing the power to be delivered during slack wind must also be supplied. A quick analysis based on industry supplied data suggests that if the wind were backed up by batteries, an onshore installation could supply power and be profitable at about $0.17/KWhr with an initial capital cost of about $20 billion for a 2,000MW installation.