When you want to retrieve data from a database, you ask for the data by using Structured Query Language, or SQL. SQL is a computer language that closely resembles English, but that database programs understand. Every query that you run uses SQL behind the scenes.
The inverter turns the DC electricity generated by the solar panels into 120-volt AC that can be put to immediate use by connecting the inverter directly to a dedicated circuit breaker in the electrical panel.
Each solar panel produces a certain number of kilowatts of energy. A 4 kW system, for example, would produce 4 kW of electricity in full sunlight for one hour. To figure cost, you'll need to know how many watts of electricity your system needs to produce.