A guy called me last February, two days into an ice storm, half his neighborhood dark. He’d bought a shiny new standby unit the year before and was furious because his air conditioner and electric range wouldn’t run. The problem wasn’t the generator. It was the size he’d picked, and nobody had walked him through what it would actually cover.
That conversation happens more than you’d think. Homeowners hear “standby generator” and picture the lights coming back on exactly like the utility never blinked. Sometimes that’s true. Sometimes you’re running a fridge, a furnace, and a couple of outlets, and that’s the deal you signed up for whether you knew it or not.
So let’s sort out the real choice in front of you: whole house vs partial generator coverage, what each one actually powers, and which one fits your home and your budget.
Key takeaways
- Whole-house coverage runs nearly everything at once; partial (managed) coverage protects a chosen set of circuits for a lot less money.
- A partial setup usually means a 10-18 kW unit; a true whole-house job often lands at 22-26 kW or higher.
- Load management can let a smaller generator behave almost like a whole-house one for a few hundred dollars.
- Your fuel line, panel space, and biggest appliances decide more than the brochure does.
What “whole house vs partial generator” really means
Partial coverage, sometimes sold as “essential circuits,” wires a small subload panel to a handful of things you can’t live without. Think furnace blower, well pump, refrigerator, a few lights, maybe the garage door. Ten or twelve circuits, tops.
Whole-house coverage backs up your entire main panel. Every circuit stays live, and in most cases you barely notice the power went out except for a brief pause during the transfer. The generator has to be big enough to carry your worst-case simultaneous load, which is where the price climbs.
The line between them isn’t as sharp as sales pages make it sound. A mid-size unit paired with smart load management sits right in the middle, and honestly that’s where most of my installs land.
The transfer switch does the real work
Both setups need an automatic transfer switch. On a partial job it’s often a small “service-rated” switch feeding an essential-loads panel. On a whole-house job it’s a full-panel switch rated for your main service, 200 amps in most modern homes. If you want the mechanics of the handoff, this walkthrough of how a standby generator actually works lays it out cleanly.
What each setup actually powers
Numbers make this concrete. Here’s roughly what different sizes carry, based on jobs I’ve done across a mix of gas and propane homes.
| Generator size | Realistic coverage | Typical use |
|---|---|---|
| 10 kW | Furnace, fridge, well pump, lights, outlets | Partial / essentials |
| 14-18 kW | Above plus one AC unit or electric water heater | Partial-plus with load shedding |
| 22-26 kW | Most of a 2,000-3,000 sq ft home at once | Whole-house |
| 36-48 kW | Large home, dual AC, electric heat, pool | Whole-house, all-electric |
The catch with electric homes is that resistance heat and heat pumps are hungry. A single electric furnace strip can pull 10 kW by itself. If that’s your setup, “whole house” gets expensive fast, and a gas furnace changes the math completely.
Before you shop, walk your panel and write down the amperage of your biggest loads: AC compressor, well pump, water heater, range, dryer. Two or three of those running together is your real design number, not the total of every breaker in the box.
What the price gap really looks like
A partial install with a 10-14 kW air-cooled unit and an essential-loads panel commonly runs $6,000 to $9,000 all in, depending on gas line length and permits. A whole-house 24 kW job with a 200-amp transfer switch is usually $11,000 to $16,000, and the big liquid-cooled units for all-electric homes push well past that.
Most of that jump isn’t the generator itself. It’s the heavier transfer switch, a possibly larger gas meter or propane tank, and the labor to feed a bigger load. I break the line items down further in this full standby generator cost breakdown if you want to see where every dollar goes.
Fuel changes the whole equation
A 24 kW unit under load can burn around 3 gallons of propane an hour. On a 500-gallon tank at 80 percent fill, that’s roughly five days of continuous running, and a lot less if it’s cold and everything’s cycling. Natural gas dodges the tank problem entirely but depends on line pressure and pipe size, which is a real limit on older homes.
When partial is the smarter buy
A mistake I see all the time is a homeowner spending whole-house money to protect a house that only really needs its heat and refrigerator kept alive. If your outages are short and rare, partial coverage is often the honest answer.
Partial makes sense when:
- Your outages typically last a few hours, not days
- You heat with gas and just need the blower and a few circuits
- Your panel or budget can’t stretch to a large unit right now
- You can live without central AC during a storm
Air-cooled units carry most partial installs just fine. If you’re weighing the engine type, the differences in air-cooled vs liquid-cooled standby generators matter more as the size climbs toward whole-house territory.
When whole house earns its keep
If you’re on a well, work from home, run a home medical device, or lose power for days every winter, the convenience of never thinking about which breaker is on is worth real money. On a job last winter, a couple with two kids and a home office told me the first full-house outage paid for the upgrade in peace of mind alone.
All-electric homes tilt this way too. When there’s no gas furnace to fall back on, half-measures leave you cold. The complete guide to whole-house standby generators is a good next read if you’re leaning this direction.
Never run any generator, standby or portable, without a properly installed transfer switch. Back-feeding a panel can kill a lineman working to restore your power. The CPSC generator safety center covers the carbon monoxide and back-feed risks worth reading before any install.
The middle path most people miss
Here’s the option that saves the most money: a mid-size generator with automatic load management. Smart switches watch the load and shed your AC or dryer for a minute when the well pump kicks on, then hand it back. An 18 kW unit with two load-shed modules can behave like a 24 kW whole-house install for a few hundred dollars in parts.
I put these in constantly now. You get near-whole-house comfort without paying for the biggest engine on the shelf, as long as you’re okay with a rare thirty-second dimming when two big loads collide.
How to make the call this week
Start by getting your real numbers, not the brochure’s. Add up your two or three largest simultaneous loads, check whether you’re on gas or all-electric, and confirm your gas line or propane tank can feed the size you want. Running through how to size a generator for your home takes about twenty minutes and stops most oversizing mistakes.
Then get two quotes, one for essentials-only and one for whole-house with load management, and compare them side by side. If you’re not sure you’re ready for a permanent install at all, a portable generator for home backup can bridge the gap while you decide. Either way, size it for how you actually live, not the worst storm you can imagine, and you’ll be the neighbor whose lights stay on.
