How to Choose the Right Whole-Home Generator: A Complete Sizing Guide

If you’ve ever sat through a multi-day power outage in Bucks County - watching food spoil, sump pumps stop running, and heat fail in January - you’ve probably thought seriously about a whole-home generator. And you’re not alone. Generator inquiries spike every time a nor’easter or summer storm moves through Montgomery County, taking down lines and leaving neighborhoods dark for days.

The challenge isn’t deciding you want a generator. It’s figuring out which one to buy and making sure it’s sized correctly for your home. Get this wrong, and you’ve spent thousands of dollars on a system that either can’t power your home adequately or is so oversized it’s inefficient. This guide walks you through the entire process.

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Why Generator Sizing Matters More Than Brand

Before comparing Generac vs. Kohler, you need to understand what you’re trying to power. A generator that’s too small will overload and shut down when your HVAC, refrigerator, and sump pump all run simultaneously. A generator that’s dramatically oversized wastes fuel and costs more than necessary.

Sizing is calculated in kilowatts (kW). Here’s a general framework:

Essential Circuit Coverage (10–16 kW)

A generator in this range powers your critical systems:

• Refrigerator and freezer
• Sump pump
• Well pump (if applicable)
• Several lighting circuits
• Phone charging and some outlets
• Basic furnace operation (heat, not central air)

This is the minimum for most Bucks County homeowners who want to get through an outage comfortably without losing food, flooding their basement, or going without heat.

Whole-Home Coverage (18–26 kW)

This range covers everything above plus:

• Central air conditioning (often the biggest draw)
• Electric stove or oven
• Electric dryer
• Multiple large appliances running simultaneously

Most homes in Montgomery County running central HVAC need at least 20 kW to operate comfortably during summer outages without compromising on anything.

Large Homes or Homes with Special Loads (26–48 kW+)

Larger homes, homes with electric vehicle charging needs, high-draw HVAC systems, or commercial properties may require generators in this range. A proper load calculation is essential at this scale.

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How to Calculate What Size Generator Your Home Needs

A licensed electrician will do this formally with a load calculation, but here’s how to think through it yourself:

Step 1: List every major appliance and its wattage. HVAC is typically your biggest single load - a central AC unit might draw 3,000–5,000 watts. Electric water heaters, well pumps, and electric ranges are also significant.

Step 2: Add up your “must-run” loads. What do you absolutely need on during an outage? For most Bucks County families: HVAC, refrigerator, sump pump, water heater (if electric), and basic lighting. Add those wattages.

Step 3: Account for startup surge. Motors (like your HVAC compressor or well pump) draw 2–3x their running wattage for a few seconds on startup. Your generator must handle these surge loads.

Step 4: Add a buffer. Professionals typically recommend sizing up 20–25% from your calculated load to account for future appliances and load variation.

This is why load calculations done by a licensed electrician are worth the time - guessing often leads to undersized generators and service calls.

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Generac vs. Kohler vs. Briggs & Stratton: Which Brand Is Right for You?

All three are reputable manufacturers. Here’s an honest comparison for Bucks and Montgomery County homeowners:

Generac

Generac is the most widely installed residential standby generator brand in the US, and for good reason. They have an extensive dealer network, wide parts availability, and a solid track record. The Guardian and Protector series cover most residential and light commercial needs. Graff’s Electric & IT is a Generac installer, and we’ve installed dozens of these systems across Bucks County and Montgomery County.

Best for: Most residential applications, homeowners who want broad local service support.

Kohler

Kohler generators are built to an extremely high standard and are particularly popular in the commercial and premium residential market. They tend to run quieter than comparable Generac units and have excellent build quality. Parts are widely available, and Kohler has strong dealer support in southeastern Pennsylvania.

Best for: Homeowners who prioritize quiet operation and premium build quality, light commercial applications.

Briggs & Stratton

The Briggs & Stratton home standby generator line (sold under the Standby Power brand) offers a competitive price point for residential use. They’re a solid choice for homeowners focused on essential circuit coverage rather than whole-home power.

Best for: Budget-conscious homeowners covering critical circuits only.

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Transfer Switch Types: Automatic vs. Manual

No matter which generator you choose, you’ll need a transfer switch - the device that safely disconnects your home from the utility grid before connecting to generator power.

Automatic Transfer Switch (ATS)

This is what most whole-home standby generator installations use. The ATS monitors utility power and, within seconds of detecting an outage, automatically starts the generator and transfers your home to generator power. You don’t have to do anything - it happens whether you’re home or away.

For families in Bucks County with sump pumps protecting finished basements, or for homeowners who travel, an ATS is practically essential.

Manual Transfer Switch

Manual transfer switches require you to physically flip the switch to connect to the generator. They’re less expensive and perfectly functional if you’re always home and comfortable with the process. Commonly used with portable generators rather than standby units.

Whole-Home Transfer vs. Load-Managed/Essential Panel

Some installations use a “load management” approach where only specific circuits are connected to the generator. This is appropriate when the generator is sized for essential circuits only. A full standby installation with a properly sized generator typically transfers the entire home.

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What Does Whole-Home Generator Installation Cost in Bucks County, PA?

Here’s a realistic range for homeowners in Bucks County and Montgomery County:

• Generator unit (Generac 18–22 kW): $3,500–$6,000
• Automatic transfer switch: $500–$1,500
• Electrical installation and wiring: $1,000–$2,500
• Gas plumbing connection: $300–$800 (if connecting to natural gas or propane)
• Concrete pad: $300–$600
• Permit fees: $150–$400
• Total installed cost (typical whole-home, 18–22 kW): $6,000–$12,000

Larger generators or more complex installations run higher. These numbers are honest estimates - actual quotes depend on your home’s panel, distance from gas lines, and local permit requirements.

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Generator Maintenance: What to Plan For

A standby generator that’s never serviced is a generator that won’t start when you need it. Here’s the basic maintenance schedule:

• Weekly automatic self-test: Most standby generators run a weekly exercise cycle automatically - you’ll hear it run for a few minutes
• Annual service: Oil and filter change, spark plugs, air filter, battery check - typically $150–$300 per visit
• Load bank testing: Every few years, a full-load test verifies the generator can handle your home’s actual demands
• LP/gas line inspection: Annually or per your gas supplier’s recommendation

Many Bucks County and Montgomery County homeowners sign up for annual service agreements to ensure their generator is ready when the next storm season hits.

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FAQ: Whole-Home Generators in Bucks County & Montgomery County

Q: How long does a whole-home generator installation take? A: A standard installation - including the concrete pad, gas connection, electrical transfer switch, and wiring - typically takes one to two days. Permitting and inspection scheduling adds time, so plan for a total project timeline of one to three weeks.

Q: Does a standby generator add value to my home? A: Generally yes. Real estate data consistently shows that whole-home generators are a valued feature, especially in areas like Bucks and Montgomery County where power outages from storms are common. Some studies suggest 3–5% added resale value.

Q: Can a generator power my electric vehicle charger? A: Yes, if the generator is sized to include that load. We factor EV charging into the load calculation when homeowners have or plan to have EVs.

Q: Do I need a permit to install a standby generator in Bucks County? A: Yes. Generator installations require electrical permits and often separate gas permits depending on your municipality. A licensed installer handles this - it’s not optional, and skipping permits creates insurance and resale complications.

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Call Graff’s Electric & IT at (215) 559-1989 or visit graffselectric.com to schedule your free whole-home generator consultation. We install Generac and other leading brands throughout Bucks County and Montgomery County, PA.