Inverter generators are a fairly new technology, using advanced electronic circuitry and state-of-the-art magnets. Inverter generators normally output AC current like most conventional generators, but the current rectified to DC voltage, folowed by it being "inverted" back to clean AC voltage, thus how it gets its name. One advantage to this inversion, is that it helps to maintain a constant flow of current to your appliance.
Often they can be very quiet. Inverter generators are more fuel-efficient in most applications due to the engine speed which adjusts according to the power load needed. Where as a standard unit the speed it fixed.
Inverter generators have several benefit, all of which are significant: fuel-efficiency, convenience, quieter operation and controlled power output. All this comes at a price, so inverter generators are more expensive, but isn't everything better more expensive?
Inverter generators have more parts than a standard generator, so they are probably less reliable. However the additional parts are generally reliable well proven technologies, so this shouldnt be a significant factor. While the engine is not going to work as hard as a conventional unit, so you might find you have superior life.
A standard or conventional, petrol generators or diesel generator or silenced generator is a fixed speed engine connected to an AC alternator. It runs at a fixed speed regardless of the load (the amount of power you are using). As your load increases the engine injects more fuel up to keep the engine speed the same. As you reduce your load the oposite is true, less fuel is used. The main alternator windings are connected directly to thi load, whereas with inverter technology that is not the case.
Like a standard generator, an inverter generators engine is connected to alternator, which produces AC electricity. However, that is where things change. In an inverter generator, a rectifier is used to convert the power to DC, capacitors can also be used to smooth it out, then the DC power is then inverted back to AC power. This system produces more consistent power independent of the engine speed. The resultant power is much "cleaner" than is possible with a conventional generator.
This is important. Products today normally use some form of microprocessor. Computers, phones, TVs, game consoles, printers are all good examples. These are sensitive to the quality of the electricity they use. Using power with unstable frequency or voltage can make these devices fail or damage them beyond repair.
Now that is a good question! Its not as easy as you would hope. Here is a short article about sizing generators that explains the basics. What size diesel generator do I need?
Investigate and look! Do you want to pay the price premium for an inverter generator? This Consumer Reports article on Inverter generators ranks a few popular models. Search and find other information on the units you are interested in and make an informed desision. Inverter generators are only really available up to 5000w, so if you need something bigger a Perkins Diesel Generator or Baudouin Diesel Generator