Get matched with top generator install pros in Pittsford, MI

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.

You can expect a diesel generator to last for up to 30,000 hours of use, which works out to 20 to 25 years with the proper maintenance, of course. That depends on how much you use it, so a diesel generator used for emergencies a couple of times a year will last a lot longer than a generator that takes over for a faulty electrical grid every month for a day or two. 

In most municipalities, you will need a permit to install a permanent home generator, including emergency backup, partial-home, and whole-home generators. A permit for a generator usually costs between $50 and $250, depending on where you live. Your electrician or certified generator installer will usually pull the permit for you—and might be required to do so by your building department—but you’ll be on the hook for the cost of the permit. You should ask your installer before agreeing to any work if they will pull the necessary permits for your project.

Whole-house generators can run continuously for extended periods, even for weeks at a time (around 400 to 500 hours), as long as they have a sufficient fuel supply. However, this type of extensive use will increase wear and tear and can shorten the generator's overall lifespan. During long periods of operation, it's important to check and refill the engine oil as needed, potentially as frequently as daily depending on the model. If your generator uses a fuel tank, ensure it is kept full to prevent unexpected shutdowns.