Power outages in Northeast Indiana aren’t rare events. Severe storms, ice, and grid failures hit the region every year, and when the lights go out, the question most property owners wish they’d answered sooner is: What size generator do I need? Buy too small, and it can’t handle the load. Buy too large, and you’ll overspend on capacity you’ll never use. Getting sizing right from the start is what separates backup power that actually works from a system that lets you down when it counts.
Why Generator Sizing Matters
A generator running at or above its rated capacity overheats, wears out faster, and can damage connected electronics when voltage regulation breaks down under stress. Oversizing causes its own problems, too. Generators operating below 30% of rated capacity are prone to wet stacking, in which unburned fuel builds up in the exhaust system and causes long-term engine damage.
The sweet spot is 70% to 80% of rated capacity under normal load. That’s where efficiency, longevity, and performance line up.
Types of Generators Explained
Portable generators are the most affordable entry point and can power a few essential circuits during short outages. They require manual startup, run on gasoline or propane, and must be operated outdoors. They’re not a practical whole-home or business solution.
Standby generators are permanently installed, connect directly to your electrical panel, and start automatically when utility power is lost. They run on natural gas or propane and are the right choice for homes and businesses that need reliable backup without manual intervention.
For commercial and industrial applications, three-phase generators are typically required to power motors, compressors, and large electrical equipment. Sizing and installation at this level is considerably more involved than residential work.
How to Calculate Generator Capacity
Generator capacity is measured in kilowatts (kW). The basic approach is adding up the wattage of everything you need to power simultaneously, then accounting for the startup surge. Motors and compressors draw two to three times their running wattage at startup, so a central air conditioner running at 3,500 watts may need 7,000 to 10,000 watts to start.
For a typical Indiana home, critical loads look something like this: central air or heat at 3,500 to 5,000 watts, refrigerator at 700 to 1,200 watts, sump pump at 800 to 1,500 watts, and lights plus outlets at roughly 2,000 to 3,000 watts. Add running watts for simultaneous loads, then add the largest single startup surge. Most whole-home standby generators for average Indiana homes fall within the 14-22 kW range.
Online generator sizing calculators help with rough estimates, but a load calculation done by a licensed electrician is the only way to get numbers you can actually rely on.
Residential Generator Sizing Considerations
The first decision for homeowners is whether they want critical circuit coverage or whole-home backup. A 7 kW to 12 kW generator connected to a critical load subpanel covers the essentials: refrigerator, lights, furnace, and sump pump. It won’t run central air or an electric range, but it keeps the household functional.
Whole-home backup requires sizing for your total potential load, including anything that could run simultaneously. Electric vehicles, heat pumps, and electric water heaters add significant demand and need to be factored into the calculation. Fuel supply matters too. A propane generator with a small tank sounds fine until a week-long January outage drains it in three days.
Commercial & Industrial Backup Power Needs
Commercial generator requirements are more demanding, and the cost of undersizing is higher. A restaurant loses inventory and revenue. A medical office faces patient safety concerns. A manufacturer may spend hours restarting equipment after an unplanned shutdown.
Commercial sizing starts with a full load analysis covering every piece of equipment that needs to run during an outage, including motors with high startup surges, HVAC, servers, and process equipment. Most commercial projects also require three-phase power, specific transfer switch configurations, and compliance with utility interconnection requirements. This is not residential work with bigger numbers. It’s a different category of project.
Common Generator Sizing Mistakes
Not accounting for startup surge tops the list. People add up running watts, add to that number, then find the generator can’t start the air conditioner because the surge demand exceeds capacity.
Sizing for today’s load without planning for future additions is another common one. If an EV charger or additional HVAC equipment is coming in the next few years, size the generator for where the load will be, not where it is now.
Choosing a portable generator for a job that requires a standby system is the mistake that most often shows up during actual outages. Portables require manual startup and fuel management in conditions that are often the worst possible time to handle either.
Professional Generator Installation Benefits
Generator installation is a legitimate electrical project. A licensed electrician handles the transfer switch installation, which is the component that disconnects your property from the utility before connecting the generator. Without a proper transfer switch, backfeed can send generator power into utility lines, creating a serious hazard for linemen restoring power.
Permits and inspections are required for generator installations in Indiana. Professional installation also includes load testing under real conditions before the job is closed out, which is the only way to confirm the system will actually perform when a real outage happens.
The Right Generator Starts with the Right Assessment
There’s no universal answer to generator sizing. What works for a home in LaGrange County is completely different from what a Fort Wayne commercial facility requires. The only way to get it right is to assess actual load, plan for startup surges and future growth, and install the system correctly.
J.O. Mory’s licensed electrical team handles backup power projects throughout Northeast Indiana, from residential standby installations to complex commercial and industrial systems. They’ll assess your property’s load, walk you through your options, and give you a clear recommendation based on what your situation actually calls for, not a generic package.
Every installation is permitted, properly configured, and load-tested before handoff. Contact J.O. Mory today or visit jomory.com to get started. The next outage isn’t something you can schedule around. But you can be ready for it.
