Energy Savings Rebate Calculator site - 4 categories

I am new at this. I am a webdesigner that are a bit in over my head with a new site proposal. The site is for the consumer to give information on current types of lights and geysers used per room. Eskom gives rebates and i need to show 3 categories and each has 3 steps: Category 1. Residential house with different rooms Office Building with different offices, kitchen etc Industrial warehouse School Step 1: Gather information on amount of lights (in the category that you chose) (and choose current ie. bulb, fluorescent or downlighter) per room and amount of lights Step 2: Calculate current usage for the whole house (ie: kitchen, bedroom1, bedroom2, bathroom, garage, store room, other) Step 3: Result - Show current usage against future usage