How Home Backup Power Works

If your house runs on a well and a septic system, a power outage isn't just an inconvenience — it's a plumbing event. No power means no water at the tap, and if you have an aerobic system or an effluent pump, it means no wastewater treatment either. Backup power is how you keep all of that running when the grid goes down.

There are two fundamentally different ways to do it. A portable generator is a wheeled unit you start by hand and feed with extension cords or a manual switch — cheap, flexible, and hands-on. A standby generator is permanently installed outside your home, wired into your electrical panel through an automatic transfer switch, and starts itself within seconds of an outage. Which one fits depends on your budget, how often you lose power, and how much of the house you need to keep running.

The rest of this article is the detail: how each type works, the transfer switch rules that keep everyone safe, what size you actually need (your well pump is the load that matters most), which fuel makes sense on a rural property, what it costs, and what not to do.

Portable vs. standby: the side-by-side

	Portable generator	Standby generator
What it is	A wheeled unit you roll out and start by hand	Permanently installed outside, wired into your panel
Starts	Manually — you pull the cord or push a button	Automatically, within seconds of an outage
Powers the house through	Extension cords, or a manual transfer switch / interlock	Automatic transfer switch (ATS)
Typical output	5,000–12,500 watts	10–26+ kW (air-cooled models cover most homes)
Fuel	Gasoline, propane, or dual-fuel (gasoline + propane)	Propane or natural gas (diesel on larger units)
Installed cost	$500–$2,500 for the unit; $900–$4,000 with a manual transfer switch	Roughly $8,000–$23,000 installed
Maintenance	Exercise it monthly; stabilize or rotate gasoline; change oil per the manual	Self-tests weekly; professional service on the manufacturer's schedule
Best for	Occasional outages, essential circuits, tight budgets	Frequent or long outages, whole-house coverage, "I don't want to think about it"

Transfer switches: the part that keeps everyone safe

A generator makes electricity. Your house's wiring is built to receive electricity from exactly one source at a time — the utility grid, or the generator. Never both. The transfer switch is the device that guarantees that, by physically disconnecting your home from the utility lines before connecting it to the generator.

There are two flavors, and they match the two generator types:

Manual transfer switch. This is a small sub-panel, usually with 6–10 circuits, mounted next to your main breaker panel. When the power goes out, you start the portable generator, plug it into an inlet box on the outside of your house, then flip each selected circuit from UTIL to GEN. The switch physically cannot connect a circuit to both sources at once. Installed cost is typically around $600–$1,200, and it must be wired in by an electrician.

Automatic transfer switch (ATS). This is the brain of a standby system. It constantly watches the utility feed; when it detects an outage, it starts the generator, waits for it to stabilize, and transfers the whole panel (or selected circuits) to generator power — all without you lifting a finger. When utility power returns, it switches back and shuts the generator down.

There's also a third, cheaper option for portable owners: an interlock kit. This is a listed metal plate installed on your main breaker panel that makes it physically impossible for the main breaker and the generator breaker to be on at the same time. It must be installed by a qualified electrician, and it has to be a listed device made for your specific panel — not a homemade bracket. The Portable Generators Manufacturers' Association (PGMA) is clear on this point: a properly installed transfer switch or interlock device are the only safe ways to connect a portable generator to your home's wiring.

What NOT to do: backfeeding

This section is the most important one in the article, so read it twice.

Backfeeding means plugging a generator into a wall outlet — usually a dryer or range outlet — with a male-to-male extension cord, so the generator energizes your home's wiring backwards. The cord itself is sometimes called a "suicide cord," and the name is earned.

Here's why it's lethal. Your home's transformer works in both directions. Power flowing backwards out of your house gets stepped back up from 240 volts to thousands of volts on the distribution lines. Lineworkers repairing those lines during an outage expect them to be dead. If your generator is energizing them, a worker touching what should be a dead line can be electrocuted — and so can a neighbor on the same transformer. It also bypasses your home's circuit protection devices, which means overloaded wiring can overheat inside your walls and start a fire, and the voltage swings can destroy appliances and the generator itself.

The usual justification is "I turn off the main breaker first, so nothing goes back to the grid." Every serious safety authority — the NFPA, OSHA, and the PGMA — treats this as no defense at all, for three reasons: you can forget (3 a.m., snowstorm, half asleep); someone else in the household can plug it in without knowing about the main breaker; and old breakers can fail to fully disconnect. Backfeeding is illegal in most jurisdictions, full stop.

The legal alternatives aren't exotic: a manual transfer switch, or a listed interlock kit installed by an electrician. That's the entire list.

Sizing: running watts vs. starting watts

Generators are sized in watts, and there are two numbers that matter:

• Running watts — what the generator can sustain continuously.
• Starting (surge) watts — the short burst it can deliver for a few seconds to get motors started.

This distinction is the whole game, because electric motors spike to roughly 2–3 times their running draw for a few seconds at startup. If you size on running watts alone, the generator will stall or trip the moment your well pump kicks on.

For a rural home, the well pump is usually the largest motor in the house and the load that determines your generator size. Some planning estimates (check your own equipment's nameplates — these are starting points, not guarantees):

Appliance	Running watts (est.)	Starting watts (est.)
Well pump, 1 HP	2,000	11,700
Well pump, 1/2 HP	1,000	7,700
Refrigerator / freezer	700	2,200
Furnace blower fan	750–800	2,000–2,350
Sump pump	800–1,000	1,300–2,500
Microwave	1,000–1,200	1,000–1,200
Lights, TV, internet, chargers	~500	~500

The method: list everything you want running at once, add up the running watts, then add the largest starting-watt spike on top (only one big motor starts at a time, realistically). That total is your minimum generator size — then round up, because running a generator at its absolute limit is hard on it and leaves no room for the freezer cycling on.

A note on the pump numbers: those starting figures are on a VA basis — locked-rotor amps from the motor spec sheet (Franklin Electric's AIM manual lists 32.2 locked-rotor amps for a 1/2 HP 230 V submersible) multiplied by 240 V. Some sizing worksheets convert locked-rotor amps to kilowatts using an assumed power factor and land around 3–4 kW for a 1/2 HP pump — that's where the smaller estimates come from. We use the unconverted figure on purpose: a generator's alternator is limited by current, and Generac's own sizing guide rates surge capability in locked-rotor amps. The VA figure is the conservative planning number. Our sizing guide shows the full math.

The companion generator size calculator walks through this arithmetic with well-pump starting watts built in. And a practical note from our well pump troubleshooting guide: know your pump's horsepower before you shop. It's on the pump or the control box, and guessing wrong here is how people buy a generator that can't start the one load they bought it for.

Fuels, with rural angles

Your fuel choice is really a storage question: how long can the fuel sit, untouched, and still work when you need it?

Gasoline. The default for portables — cheap, available everywhere, and every small engine runs on it. The problem is shelf life: gasoline starts to degrade in roughly 3–6 months untreated (a fuel stabilizer stretches that, but it doesn't make it immortal). That means a gasoline generator is a maintenance commitment — you rotate the fuel or the carburetor gums up and it won't start when the lights go out. The CPSC's rules: store gasoline outside living areas in properly labeled, non-glass safety containers, never near a fuel-burning appliance, and always shut the generator down and let it cool before refueling (spilled gasoline on hot engine parts can ignite).

Propane. The rural favorite, and it's not close. Propane does not degrade — it has an effectively indefinite shelf life in a sealed tank, so the fuel you buy this year works just as well five years from now. If your home already heats with propane, you likely have a 250- or 500-gallon tank sitting there, which is a ready-made fuel reserve. Two caveats: tanks are filled to 80% by rule (room for expansion), and in very cold weather a small tank can struggle to vaporize fuel fast enough for a big load — that's one reason standby installers size the tank to the generator, not just to the house. The other reason propane dominates rurally: per EIA data, about 83% of propane-heating households are in rural areas beyond the reach of natural gas distribution infrastructure. If there's no gas main on your road, propane is your piped-fuel equivalent.

Natural gas. The most convenient fuel if you have it — unlimited runtime, no refueling, no storage. The catch is availability: if your rural road doesn't have a gas main, this option doesn't exist for you. (One spec-sheet footnote worth knowing: a typical 22 kW standby makes its full 22 kW on propane but about 19.5 kW on natural gas, because propane packs more energy per unit.)

Diesel. Common on larger standby units and farm PTO generators. Diesel stores better than gasoline (roughly 6–12 months untreated) but it can grow microbes and gel in cold weather, so it needs attention too. For most homes, diesel only enters the picture at sizes where air-cooled propane units run out.

How long will the fuel last? Work one real example. A popular 22 kW air-cooled standby (Generac's Guardian 7042/7043) burns about 2.5 gallons of propane per hour at half load and about 3.9 at full load, per the manufacturer's published specs. A 500-gallon propane tank holds 400 usable gallons at the standard 80% fill — so at half load, that's roughly 150+ hours, or the better part of a week, without a delivery. That's the math that makes propane standby systems so attractive in places where outages last days, not hours.

Where to put the generator

Placement rules are different for the two types, and they're not suggestions.

Portable generators go outside, at least 20 feet from the house, with the exhaust pointed away from the building — never in the garage, basement, shed, crawlspace, or on the porch, even with doors and windows open. This is the CPSC's rule, and it's written in the language of experience: carbon monoxide is colorless and odorless, it can kill within minutes, and an average of nearly 100 people a year die in the U.S. from CO poisoning tied to portable generators. Close any windows near the generator, and keep working CO alarms on every level of the house. The cords matter too: each extension cord's wattage rating must exceed the total wattage of everything plugged into it, and the cord has to be long enough to let the generator sit 20 feet out.

Standby generators are designed to live close to the house, but the clearances are specific. Generac's installation guidelines (based on NFPA 37 testing) allow the enclosure as close as 18 inches from a stationary wall, but require 5 feet from any operable opening — windows, doors, fresh-air intakes — plus 3 feet of service clearance at the front and ends and 5 feet of open space above. Your installer handles this, but know the numbers so you can sanity-check the proposed spot. Local codes can be stricter than the manual, so the installer's permit process is doing real work here.

What it costs, honestly

Setup	Typical installed cost
Portable generator alone (extension cords only)	$500–$2,500 for the unit
Portable + manual transfer switch	$900–$4,000 total
Essential-circuit standby (automatic, selected circuits)	$6,000–$11,000
Whole-home standby	$8,000–$23,000

Those standby ranges come from national cost guides and move around a lot. What moves the number:

• Generator size — the unit itself is the biggest line item; a 26 kW costs notably more than a 14 kW.
• Fuel work — a new propane tank and gas line, or a long trench from the existing tank, can add thousands. The closer the unit sits to the fuel supply and the electrical panel, the cheaper the install.
• Electrical work — panel upgrades, long wire runs, and the transfer switch itself.
• Site prep and permits — concrete pad or gravel bed, permits, inspections; some jurisdictions are easy, some aren't.
• Maintenance contracts — many installers sell annual service plans; budget for them rather than discovering them later.

Maintenance: the part people skip

A generator that hasn't run in two years is a very expensive paperweight. The maintenance isn't hard; it just has to actually happen.

• Exercise it. Standby units self-test on a schedule (typically a brief weekly run) — make sure the feature is enabled and the unit isn't throwing fault codes you haven't noticed. Portables need a monthly run under load.
• Fuel discipline. Stabilize stored gasoline and rotate it, or run the carburetor dry after each use. Propane and natural gas need no fuel maintenance, which is half their appeal.
• Oil and filters. Follow the manufacturer's schedule — portables need oil changes based on run hours (check the level before every long run), and standby units need professional service on the book's interval, including the battery that starts them. A dead starter battery is one of the most common reasons a standby unit fails to start.
• Test the whole system yearly. Not just the generator — flip the transfer switch (or run the ATS test mode) and confirm the well pump actually starts and the house actually transfers. Finding out your interlock sticks, or your pump's starting surge trips the breaker, during an ice storm is the wrong time.

Which one is right for your situation?

Your situation	The better pick	Why
Outages are rare and short; budget is tight	Portable + extension cords	Cheapest path to keeping the fridge cold and phones charged
You lose power a few times a year and want the furnace, well pump, and fridge on circuits	Portable + manual transfer switch	Real capability for a few thousand dollars; you do the work of starting and switching
You're away from home often, or outages last days	Standby + ATS	Starts itself whether you're home or not; no fuel runs in a storm
Medical equipment that can't go dark	Standby + ATS	Automatic start is the point — seconds matter
You already have a big propane tank	Standby on propane (or dual-fuel portable)	The fuel infrastructure is already paid for
No natural gas, no propane tank, small budget	Dual-fuel portable	Run gasoline now; you can switch to propane later without buying a new generator

When a generator won't help

Honesty section, as always:

• A dry well. A generator powers the pump; it doesn't make water. If the aquifer isn't yielding, the pump runs dry and the generator just watches. Diagnose water problems first — our no-water triage tool walks through the safe homeowner checks in order.
• An undersized generator. If the well pump's starting surge trips the breaker every time it cycles, you bought too small. This is the most common generator regret, and it's why the sizing math above (and the calculator) exists.
• Fuel you don't have. A gasoline portable with an empty tank and a closed gas station is decoration. Size your fuel stockpile to your realistic outage length, not your optimistic one.
• Electronics sensitivity. Basic portable generators produce rougher power than the grid. Inverter generators produce steadier, cleaner power that's kinder to electronics and sensitive controls — if you're running a VFD-controlled well pump off a portable, check the drive manufacturer's power-quality guidance first. (Our VFD comparison flags this as an open question worth confirming with the manufacturer.)
• Problems that aren't power problems. A generator doesn't fix a failed pressure tank, a clogged filter, or a septic system that's backing up for non-electrical reasons. Keep the well troubleshooting guide bookmarked alongside this one.