To predict how much money you will spend on electricity while renting an apartment with three friends, you would need a combination of the following data points: 1. **Cost per kilowatt of electricity**: This will help you calculate the total cost of electricity based on usage. 2. **Average monthly electric bill for each roommate from the last year**: If you have access to this data, it will give you insights into how much electricity consumption typically costs for each individual, which can then be extrapolated to your situation. 3. **Average monthly electric bill for 4-person households in your community**: This can help provide a baseline expectation of what a household of similar size might spend, factoring in various local usage patterns. 4. **Total amount of electricity used by an individual in one year**: This information allows you to estimate your total usage, which can then inform your cost calculations based on the cost per kilowatt. By analyzing a combination of these data points, you can develop a more accurate estimate of your potential electricity costs while living with your roommates. If you have to pick just one or two, starting with the cost per kilowatt of electricity and the average monthly electric bill for 4-person households in your community would be the most useful.