You can spend $400 on a hobbyist generator at a chain hardware store, or $20,000 on a massive standby generator. Accurately determining the watts you need will help you get a generator that can meet your electrical demands without spending too much.

Portable generators
A basic commercial-quality gasoline-powered 5kW portable generator will cost around $600 or $800. Bump the power up to 11kw and you're looking at spending around $2,300. These "contractor-grade" generators are designed to be hauled around and stand up to rough usage.

While this is more than you'd pay for a retail store generator, those won't have the durability, dependability, and power that a portable generator from a dealer offers. You also won't be able to find much in the way of service if your low-end generator needs repair - the usual solution is to toss it and get a new one.

Portable generators are very commonly rented, too. Prices can be as low as $75/week, so for short-term power needs, renting is a viable option.

Standby generators
As a very loose rule of thumb, standby generators cost $300 to $500 per kW, installed. The prices listed below include delivery, setup, connecting to your home, and the required transfer switch, which can cost around $800 to $1,500 on its own.

• 12 kW: $4,000 to $6,000
• 15 kW: $4,500 to $7,000 (the most common size for residential generators)
• 25 kW: $9,000 to $13,000
• 40 kW: $12,000 to $16,000
• 75 kW: $20,000 and up
• Find out what BuyerZone users paid for Home Generators.

Generator service contracts and warranties
If well-maintained, a generator can last quite a long time. However, they do require consistent maintenance. Most of the wear is concentrated on the motor: changing oil and spark plugs, checking coolant, and other engine maintenance all need to be done on at least an annual basis

For this reason, it's best to choose a dealer who offers a service plan that includes yearly visits. Pricing for a service plan will vary according to the size and type of generator you select - for example, large, liquid cooled generators take longer to service.

Your dealer should offer at least a two year parts and labor warranty with the sale `of a new generator. Make sure you know what the warranty covers: some are bumper-to-bumper, while others cover only certain parts of the generator.