To get the best out of a solar panel, the angle of incidence of the sun should be between 20 and 50 degrees. Solar power via photo-voltaic cells are usually the most expensive method to harnessing renewable energy, but is falling in price as technology advances and public interest increases. It has the advantages of being portable, easy to use on an individual basis, readily available for government grants and incentives, and being flexible regarding location (though it is most efficient when used in hot, arid areas since they tend to be the most sunny).[3][42] For those that are lucky, affordable rental schemes may be found.[39] Concentrated solar power plants are typically used on more of a community scale rather than an individual household scale, because of the amount of energy they are able to harness but can be done on an individual scale with a parabolic reflector.[42][43]