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Whole-Home or Essential Circuits: How Sizing Works

Volt Pro Services · Farragut, TN · August 14, 2026

Whole-Home or Essential Circuits: How Sizing Works

Most generator conversations start with kilowatts. That is the wrong end of the problem. Here is what a transfer switch actually does, which loads in a west Knox house drive the math, and how load shedding lets a smaller unit carry a bigger home.

Key Points

  • The transfer switch, not the engine, decides whether you get the whole house or a set of circuits
  • The useful question is what has to keep running, not how many kilowatts you want
  • Compressor startup, well pumps, and refrigeration dominate the calculation out here
  • Load shedding lets a smaller unit carry a larger house without anyone noticing
  • Fuel supply and lot clearances shape the answer as much as the panel does

Start With the Transfer Switch, Not the Engine

That switch comes in two forms, and choosing between them is the actual decision in front of most Farragut homeowners. A service-entrance or whole-panel switch sits ahead of your main panel and transfers the entire house at once. Every breaker you already have stays where it is, and during an outage the house behaves the way it always does. The alternative is a dedicated essential-loads subpanel: we install a second, smaller panel next to the main one, move the circuits that genuinely matter into it, and the transfer switch feeds only that subpanel. Everything else in the house simply stays dark until the utility returns.

The Honest Question Is What Must Keep Running

Homeowners usually open with a number they read somewhere. A better starting point is a walk through the house asking what would actually hurt during a two-day outage in January. Heat is nearly always first. Refrigeration and a freezer come next, because that is real money sitting in a box. Then well pump if you are on one, sump if the basement needs it, a few lighting circuits, internet and the router, and increasingly a home office that has to stay online because somebody’s workday does not pause for a downed line on Kingston Pike.

Load Shedding Lets a Smaller Unit Carry a Bigger House

That approach is why the whole-home versus essential-circuits framing is a little too clean. Plenty of installs land in between: a whole-panel transfer switch with two or three managed loads, giving you every outlet and light in the house without paying to carry the theoretical worst case where the range, dryer, and both compressors run at once. Our Farragut generator page covers how we work through that decision on site.

Fuel Changes the Math

Farragut splits cleanly on fuel. Inside the platted subdivisions there is usually natural gas at the street, and that is the easier system to live with: it never runs out, there is no tank in the yard, and nobody has to schedule a delivery during an ice event. What it does require is a gas line sized for the generator’s demand on top of whatever the furnace, water heater, and range already pull. Pressure at the meter is a real constraint, and an undersized run will starve a large unit under load even though the pipe looks adequate on paper.

On the outlying lots without a gas main, propane is the answer, and it changes the conversation. Propane carries a bit more energy per unit than natural gas, but you are now sizing a tank for run time, not just sizing an engine. A larger unit burns through a tank faster, which is one more argument for the essential-loads or load-shedding approach on a property where a delivery truck may not make it up the driveway for several days. We size the tank against realistic run hours and coordinate the gas work rather than leaving you to sort it out afterward.

Siting It on a Farragut Lot

Placement gets decided by four things at once: manufacturer clearances from the structure and from openings, exhaust direction relative to windows and the neighbor’s house, sound at the property line, and what the lot and any subdivision covenants will tolerate visually. Generators need clear air on all sides for cooling, they cannot sit under a deck or crowd a soffit vent, and the exhaust needs to leave in a direction nobody is standing. A weekly exercise cycle at a reasonable hour matters more in a Farragut subdivision than it does on acreage, and the pad location decides whether that is a non-event or a standing complaint.

Distance also has a cost. Setting the unit at the far corner of the lot for sightline reasons means a longer gas run and a longer conductor run back to the transfer switch, and both have to be sized for it. It is usually cheaper and better to find a spot near the meter and the panel that is screened by landscaping than to fight the physics of a long run. We work that out during the site visit, before anything gets poured.

What Happens the First Time It Runs Unattended

Beyond that it is engine maintenance on a schedule, oil and filter, plugs, air filter, and a battery load test, plus an actual transfer test to confirm the switch still moves. When the first real outage arrives you should be somewhere else entirely and find out from a text message or from a clock that did not blink. Commissioning is what earns that confidence: we drop utility power on purpose, watch the transfer, run the house under real load, and confirm the return. See finished installs in the project gallery, or request a quote and we will walk your panel and your list of must-run circuits with you.

Frequently Asked Questions

Do I need a whole-home generator or will essential circuits do?

It depends entirely on what must keep running and on how the house is built. A whole-panel transfer switch keeps everything behaving normally, while an essential-loads subpanel carries heat, refrigeration, well, sump, and a few key circuits on a smaller unit. Load shedding often bridges the two. Call (865) 256-0876 to talk it through.

What actually drives the size calculation?

Starting surge, mostly. A heat pump or AC compressor pulls several times its running current at startup, and a well pump does the same. Two large motors that could start together often set the size by themselves, well before the lighting and outlet loads matter. Request a quote and we will run the numbers on your house.

Is natural gas or propane better in Farragut?

Inside the subdivisions with gas at the street, natural gas is simpler because it never runs dry and there is no tank to place. On outlying lots propane is the practical choice, and there the tank gets sized for realistic run hours, which is one reason a smaller managed system often makes sense out there.

How loud is it, and where can it sit?

Clearances from the house and from windows, exhaust direction, sound at the property line, and subdivision sightlines all constrain the pad location. Setting it far from the panel to hide it adds gas and conductor length, so the better answer is usually a screened spot near the meter. See the Farragut generator page.

What maintenance does a standby unit need?

It runs a short exercise cycle every week or two on its own, and that cycle is what catches a weak battery before an outage does. Annually it needs oil and filter, plugs, an air filter, a battery load test, and a transfer test. Call (865) 256-0876 to schedule service.

Will it really start with nobody home?

That is the entire purpose of an automatic transfer switch. It senses the utility drop, starts the engine, transfers the load, and reverses the process once utility power proves stable again. We verify all of it under real load at commissioning rather than on a no-load start.

Standby Power, Sized to Your House

We start with the circuits that have to stay alive, then pick the switch, the unit, and the fuel around that list. Permits pulled, transfer verified under load.

Call (865) 256-0876 Spark My Project

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