Load variation, from minimum demand to maximum demand, is normally met with cycling plants, such as natural gas and coal, which have lower capital cost but higher variable costs (mainly fuel). Peaking plants (generally oil-fuelled) are used to provide for peak load and are therefore operated for only a few hundred hours per year. The two Kirchhoff laws describe the flow of electric current through an integrated system and indicate that electricity will take the way of least resistance rather than the geographically shortest route.