Some energy resources are more reliable than others. The non-renewable sources are the most reliable as they can be used at any time. Whereas, the renewable sources normally depend on the weather. This means that if there is no wind, or no sun (night-time), or no waves then no electricity can be generated. Some energy resources are better placed in certain places. For example, energy from the sun (solar panels) should be placed in sunny places or countries and wind turbines (wind) should be used in windy places