An Earthship does not require external support to sustain itself. Instead, it is built to use resources available from its natural surroundings. For example, windows are placed so that sunlight is shone inside the house to be used for heating. Electricity is generated by solar panels and stored in batteries. The roofing collects rainwater that is filtered and used for drinking and various household activities such as cooking and washing. Used water from sinks and showers is reused to water indoor plants and after that for toilet flushing.