solar panel

  The economics of rooftop solar are dominated by how your utility values the electricity you send back to the grid. There are three broad models in use around the world, and knowing which one applies to you is essential before you sign a contract. Net metering is the friendliest arrangement. Your meter runs both ways. Every kilowatt hour you export is credited at the same retail rate you pay when you import. At the end of the billing cycle you owe the difference. In a full net metering regime, a system sized to your annual consumption can theoretically wipe out your bill. There are several flavours of net metering. True net metering nets everything at retail rates. Net billing separates the import and export sides and pays exports at a different, usually lower, rate. Virtual net metering allows multiple accounts to share the output of a single system, which is how community solar projects work in many jurisdictions. Ask your utility exactly which model applies to your account and ...

  Every solar panel you have ever seen is a stack of very thin silicon wafers sandwiched between glass, plastic and a metal frame. The magic happens inside those wafers. Silicon is a semiconductor, which means it can be nudged into carrying electricity when it is hit by light. Manufacturers take pure silicon and deliberately contaminate it with two different substances, usually phosphorus and boron. The result is two layers with opposite electrical charges pressed against each other. This is called a p-n junction and it is the heart of every photovoltaic cell on the planet. To make silicon behave this way, foundries start with quartz sand, reduce it in an electric arc furnace, and then refine the resulting metallurgical silicon until it is close to nine nines of purity. That refined silicon is then either grown as a single crystal using the Czochralski process or cast into large blocks and sliced. The wafers that come out of this process are astonishingly thin, often less than two ...

  The single most useful number when planning a solar system is your annual electricity consumption in kilowatt hours. Dig out twelve months of utility bills and add them together. If your provider only shows you monthly totals in currency, look for the small print or log into the online portal where the raw kilowatt hour figure lives. Most households in Europe use somewhere between three thousand and six thousand kilowatt hours a year. In the United States the range is closer to eight thousand to twelve thousand because of air conditioning and larger homes. Once you know your annual demand, the next question is how much of it you actually want to cover with solar. Grid-tied systems almost never aim for one hundred percent because the last twenty percent is disproportionately expensive. A common sweet spot is to offset seventy to ninety percent of your yearly consumption. That gives you the biggest financial return without paying for panels that will spend half the year exporting e...