I use this project on a unit on sustainability. It is a home energy audit where the student starts by examining their own electric bill and then goes through their house to determine how much each light, appliance, and other items contribute to their bill. The student then has to determine how close their actual electric bill is to their calculations and why it might be off. The purpose is to expose them to the amount of energy used and what the major "power hogs" are. The final part of the project has them create a plan to reduce their energy use (and thus their bill and greenhouse gas emissions) and estimate how much this can save them. Included are charts which allow them to estimate how many watts different appliances and other items use, information on how to convert watts and time used into kilowatt hours as seen on their bill and the points for each section. My Energy presentation, where students research different energy sources is a good follow up to this project.