The smallest turbines, costing a few hundred pounds, are designed to charge up a 12 Volt battery in a boat or caravan. To make a decent contribution to household energy use, a much larger turbine is needed. The rated power of a turbine is the power produced at its ‘rated’ wind speed (often 10m/s). The overall performance of a turbine is usually displayed using a 'power curve' - a graph of power output against wind speed.
Domestic wind turbines are typically rated between 1kW and 10kW. Many factors affect how much energy you’ll get, but a rule of thumb is that a 1kW turbine on a good site should generate 1000kWh over a year (the average UK household uses around 3700kWh of electricity annually).