The influence of deployment of planned wind farms on the power output and energy yield of wind farms located in close proximity at downwind sites is investigated. The atmospheric model Weather Research and Forecasting (WRF) has been employed to simulate wind resource and energy yield from wind farms in the Baja California region of Northern Mexico. Accuracy of predicted wind speed and wind turbine energy supply are evaluated against full-scale measurements from a met-mast and from each of five 2 MW turbines at the La Rumorosa wind-farm. For this wind farm location, wind speed distribution is predicted to within 1.4% and the energy supply from the farm predicted to within 5.25%. Accuracy depends on the boundary layer model and atmospheric dataset employed. Wind farms are modelled using the scheme developed by Fitch et al. (2012) in which a momentum sink and turbulent kinetic energy source are defined as a function of the turbine thrust coefficient and power output, each of which vary with wind speed as defined by the manufacturer. Planned farms of up to 72 MW installed capacity are defined in terms of turbine number, rated power and spacing at four sites such that each farm operates with a typical capacity factor. For a single farm of 2 MW turbines located 10 km upwind, wind speed at the case study wind-farm is reduced by 3.00% and power output reduced by up to 5.84%. These deficits increase if 5 MW turbines are deployed rather than 2 MW turbines due to the development of a longer far-wake. The net energy supply from several sites in the region is assessed.