Whole House Generator Buying Guide

A sudden, prolonged power outage shouldn’t compromise your comfort or disrupt your life. That’s why a whole-house generator is the ultimate safety net. Unlike standard options that only manage the essentials, a whole-house unit can back up your entire home, making it feel as if the outage never happened.

This expert guide will help you refine your selection and secure the best whole-house generator for your needs.

What is the difference between home standby and whole-house generators?

While a standard home standby generator (typically 9kW to 20kW) is capable of powering mission-critical items like a refrigerator and sump pump, a whole-house generator is engineered for significantly more demanding applications.

Whole-house models feature more powerful, often liquid-cooled engines, enabling extended run times, reduced noise, and longer maintenance intervals. This sophisticated design provides the capacity and reliability needed to maintain full functionality across your entire home.

Benefits of Whole-House Generators

Whole-house generators are a more powerful alternative to standard home standby units, offering anywhere from 22 to 48kW of power. This added power comes with added peace of mind, knowing your space will be fully functional. Not only do they offer longer maintenance intervals, but they are also more fuel efficient, quieter, and a more effective backup for the entire home.

Air-Cooled vs. Liquid-Cooled Generators

Choosing the right cooling system is essential for performance and longevity, particularly given your climate and power demands.

Air-cooled generators are less expensive, lighter, and easier to install than liquid-cooled generators. They are an effective, budget-friendly option in moderate or cooler climates. The downside to air-cooled generators is that air does not absorb heat as effectively or consistently as water, so air-cooled generators are limited in their power output, typically accommodating only up to 26 kW. Air-cooled generators also do not handle excessively hot climates like the Southwest very well.

Liquid-cooled generators absorb heat much more effectively and can handle significantly higher power outputs than air-cooled generators, even as high as 150kW or more. They work well in all climates. Their major downside is their complexity, which results in higher upfront installation costs. For many residential homes, a liquid-cooled whole-house generator would be considered “overkill,” although more and more homeowners are opting for them, especially in areas prone to power outages.

3 Steps to Pick the Best Whole-House Generator

Selecting the ideal unit requires a specialized blend of selection and expertise. Use these steps to ensure a flawless integration.

Step 1: Choose a Reliable Fuel Source

The fuel source is a critical component of your generator system. Whole-house generators typically utilize one of three options:

• Natural Gas (NG): A continuous, piped fuel source. Requires verification that your gas meter and lines are correctly sized to handle the generator’s consumption.
• Liquid Propane (LP): Stored in an onsite tank. A highly accessible option in many areas but requires a large enough tank to sustain the generator during an extended outage.
• Diesel: Stored onsite. Often preferred for its easy accessibility and long-term storage in more remote locations, though it also requires a dedicated storage tank.

Your installation professional will verify the feasibility and sizing requirements of your chosen fuel source before installation begins.

Step 2: Pick the Right Size Whole-House Generator(kW)

Proper sizing is the most crucial step in choosing a whole-house generator. The generator’s Kilowatt (kW) rating determines the total electrical load it can handle.

How to Calculate the Right Generator Size

1. Identify Loads: Locate the manufacturer’s data plate on every major appliance (HVAC, well pump, commercial refrigerator) to determine its starting amperage.
2. Calculate Watts: Use the formula: Starting Amps x Volts = Watts. Divide the result by 1,000 to get kilowatts (kW). Remember, central air conditioning units are often the single largest load.
3. Apply the Buffer: Select a generator with a rating that is 20% to 25% higher than your peak calculated load. This margin ensures the unit operates comfortably at about 80% capacity, providing flexibility if your power needs grow over time.

Step 3: Pick the Automatic Transfer Switch (ATS)

An Automatic Transfer Switch (ATS) is the brain of your system. It constantly monitors utility power, and the moment an outage is detected, it seamlessly performs two critical actions:

• It signals the generator to start.
• It safely disconnects your home from the utility line before energizing your electrical panel with generator power.

To select the right switch, you must match its amperage to the amperage of your home's main electrical service panel (usually 200 amps). If you have a 200-amp service, you must use a 200-amp transfer switch. This step ensures safety and proper functionality, completing the expert integration of your power solution.