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The cost to install a whole-house generator averages $5,200, with a typical price range of $1,500 to $8,900. However, total costs can vary from $400 for a small portable unit to over $18,000 for a large-capacity system. The most significant cost factor is the generator's size and capacity, but other variables include the brand, fuel type, and labor for assembly and installation.

Generator costs can be broken down by type:

• Portable or Emergency Backup Generators (1kW–7.5kW): $500 to $2,000

• Partial-Home Generators (9kW–20kW): $2,000 to $6,500

• Whole-House Generators (22kW–48kW): $5,000 to $18,000

To avoid paying for more power than you need, consider hiring an electrician to calculate the electrical load for your essential appliances. It is also recommended to get at least three quotes to find the best deal for your specific needs and budget.

As a safety measure, you should always turn off the main breaker while operating your generator’s backup breaker. In addition, you should also switch off all appliance breakers so you don't have a power surge when the main breaker turns back on. And finally, turning off the main breaker prevents back-feeding, which endangers utility workers with the risk of electrocution. Back-feeding could also destroy the electrical circuits of your neighbors if they use the same power network.

To determine the right size generator for your house, you should calculate the total wattage of the appliances and devices you want to power during an outage. List all essential items, note their start-up wattages, and add them together.

Here are some typical wattage requirements for common appliances:

• Refrigerator: 600 watts

• Large dehumidifier: 700 watts

• Large window air conditioner: 1,400 watts

• Water heater: 3,000 to 4,500 watts

• Electric furnace: 5,000 to 25,000 watts

A 7,500-watt generator might be sufficient for essentials like a refrigerator, freezer, well pump, and lighting circuits. However, for high-demand items like a water heater or furnace, a whole-home generator is a better choice. A portable generator may be enough if you only need to power a few critical items.

While home square footage can offer a rough estimate, it is not always a reliable indicator. For reference, here are some typical generator sizes based on square footage:

• 1,000 sq ft: 6–9 kW

• 1,500 sq ft: 7–10 kW

• 2,000 sq ft: 10–14 kW

• 2,500 sq ft: 12–16 kW

• 3,000 sq ft: 16–20 kW+

For the most accurate sizing, consult a professional who can calculate your home's peak and average power consumption and recommend the optimal generator.

A portable generator can supply power to selected appliances and circuits in a home, but it's generally not designed to handle the entire household's electrical needs simultaneously. Portable generators have limited wattage capacity, so they are only designed to power essential devices and electronics temporarily until local power is restored. If your power needs outweigh the capabilities of a portable generator, consider installing a whole-home generator instead.