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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.

There is no blanket figure for a residential home’s electrical load, since load varies by the size of the home, how many appliances are used, and the efficiency of their electrical systems. Typically, however, it’s safe to assume 40 to 60 amps is the average electrical load of a residential home. 

Costs depend on the property size, audit complexity, and whether additional testing (e.g., blower door) is included.

Motion-sensor lights use one watt while on standby and five watts while turned on. They’re usually on for one hour over a 24-hour period, bringing the total wattage to about 28 watts per day. LED lights use around 6.5 to 8 watts while on. If you leave an LED light on all night, with night ranging from 10 to 14 hours, you’re looking at using 65 to 112 watts a night. You can minimally cut your wattage in half by switching to a motion-sensor light.