Michael Faraday invented the generator in 1831 in England. Generators work by converting mechanical energy into electrical energy using the principles of electromagnetic induction. There are several types of generators including portable, standby, inverter, diesel, gasoline, solar, natural gas, and hydrogen generators, which differ in their fuel source, size, and intended use. Common uses of generators include providing backup power at construction sites, offices, and industrial facilities. Leading generator manufacturers are Mahindra, Honda, Caterpillar, Cummins, and Aggreko. While generators provide emergency power, they can also be expensive to purchase and operate, with some parts also costly.