Get matched with top generator install pros in Peterborough, NH

No, you should never plug a generator directly into a wall outlet in your house. This practice is extremely dangerous, often illegal, and can cause "back-feeding," where power from the generator flows back into utility lines, creating a life-threatening hazard for utility workers. It can also damage your home's electrical system, including appliances like pumps and HVAC fans. If the main power is restored while the generator is connected, it can destroy the generator and cause an electrical fire. To safely connect a generator, you must use a professionally installed transfer switch or an interlocking kit, which prevents back-feeding by disconnecting your home from the utility grid before the generator provides power.

Whole-house generators need to be installed on level ground several feet away from walls and other objects. Because they tap into the electrical system directly, they usually need to be close to your home electrical panel for a transfer switch installation. It also helps with installation if they are near to a gas line or propane tank installation.

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.

Costs depend on generator type, labor, and additional wiring or transfer switch requirements.