There are two ways to get power from a portable generator into a house, and almost every argument about extension cords, interlock kits and transfer switches is really an argument about which one you are doing.
You are either powering things — a fridge, a couple of lamps, a phone charger — or you are powering circuits, which means the furnace, the well pump, the ceiling lights and the outlets already in your walls.
Things take cords. Circuits take equipment bolted to your panel by someone licensed to do it. The methods below are not a difficulty ladder where you climb as high as your nerve allows. They are answers to two different questions.
But before either question, there is a gate that can disqualify every combustion generator method on this page, and it has nothing to do with wiring.
The 20-foot rule comes before any wiring decision
The U.S. Consumer Product Safety Commission's current instruction, issued ahead of the 2026 hurricane season, is specific about the distance:
“Operate generators outdoors only, at least 20 feet from homes and buildings, with exhaust directed away from windows, doors and vents.”
The same release rules out the places people actually put them: never inside homes, garages, basements, crawlspaces or sheds, even with the doors and windows open.
This is a gate rather than a tip. If your only sheltered spot is an attached garage, or the only place the cord reaches is six feet from a bedroom window, you do not have a placement problem to work around. You have a method that is not available to you.
The scale is worth stating once, with its reporting period attached. CPSC's technical report counts 742 deaths from portable generator carbon monoxide between 2012 and 2022, a reported minimum as of April 2023 with the last two years still incomplete. An earlier CPSC release put the annual average at about 85 deaths across 2017 to 2019.
The question that picks your method
Once placement is settled, one question does the rest of the work.
Are you powering things, or powering circuits?
Things are appliances with plugs. A refrigerator, a chest freezer, a space heater, a router, a few lamps. Every one of them can be reached with a cord, and no part of your house wiring is involved.
Circuits are what your walls already carry. The furnace blower, the well pump, the septic pump, the ceiling lights, the bathroom outlets. None of those has a plug you can reach, which is the actual reason a panel connection exists.
Cords
Power things
Appliances with plugs, no house wiring involved
Interlock or transfer switch
Power circuits
Hardwired loads: furnace, well pump, lights
20 ft
Applies to all of them
CPSC placement, exhaust pointed away
That framing also corrects a claim you will read on several of the pages that rank for this search: that cords limit you to one cord's worth of power. They do not. A 10,000-watt generator has several receptacles, and a rated four-outlet distribution cord splits one of them further.
What cords cannot do is reach a load with no plug. If your list is entirely appliances, the cheapest method is also the correct one, and you are finished after the next section.
Method 1: cords straight to the appliances
The whole method is a heavy-duty, outdoor-rated extension cord from the generator to the appliance, sized for the load and long enough to keep the machine 20 feet away.
Texas's insurance regulator, which publishes one of the better public guides on running a portable generator, makes the cord specification the substance of the advice rather than an afterthought: outdoor-rated, heavy duty, undamaged, and rated for what you are asking it to carry.
Do
- Use outdoor-rated, heavy-duty cords long enough to keep the generator 20 feet out.
- Check the cord's amp rating against the appliance, not against the generator.
- Plug appliances directly into the generator's own receptacles where they reach.
- Run cords through a gap you can close around them, or use a through-wall kit.
Don't
- Daisy-chain cords to make up the distance.
- Use an indoor cord because it was the one in the drawer.
- Prop a window open on the exhaust side to get a cord in.
- Assume a cord can carry whatever the generator can produce.
The honest limitation is the one you can see from the driveway: no matter how many cords you run, the furnace has no plug. When your outage list includes heat, water or the lights in the ceiling, cords have run out of road and you are in the second category.
Method 2: an inlet box and a panel interlock
This is the arrangement most homeowners end up with, and it has two parts that get confused with each other.
The inlet box is a weatherproof male inlet on an exterior wall. A cord runs from the generator to it. It is a connection point and nothing more; it prevents nothing.
The interlock is the part that matters. It is a listed metal plate on your panel that makes it mechanically impossible to have the main breaker and the generator breaker on at the same time. One must be off before the other can move.
That mechanical impossibility is the requirement, not a feature. NEC Article 702, which governs optional standby systems, puts it in 702.5, Interconnection or Transfer Equipment: the equipment must be listed, designed and installed so as to prevent the inadvertent interconnection of the sources of supply.
The word doing the work there is inadvertent. A rule you can follow correctly is not the same as a rule you cannot break, and the code asks for the second one.
The trade-off against a transfer switch is real. An interlock energises the whole panel, so nothing decides for you which circuits are live: you manage the load by leaving breakers off. That is cheaper and more flexible, and it puts the discipline on the person at the panel.
Method 3: a manual transfer switch
A transfer switch is a separate enclosure beside the panel holding a chosen set of circuits, usually six to twelve, each with its own switch and often its own little wattmeter.
During an outage you flip only those circuits to the generator side. The choice of what gets backed up was made at installation, not at 2am with a flashlight.
That pre-commitment is the whole argument for it. It is also the argument against it: adding a circuit later means going back to the electrician, and circuits you did not choose stay dark no matter how much capacity the generator has spare.
- Interlock energises
- The whole panel
- Transfer switch energises
- Only its own circuits
- Interlock, load managed by
- You, at the breakers
- Transfer switch, load decided
- At installation
- Interlock, adding a circuit
- Turn its breaker on
- Transfer switch, adding one
- Call the electrician back
- Source isolation
- Both: mechanically enforced
A third arrangement exists where your utility permits it: a listed meter-mounted transfer device that sits between the meter and its socket. Availability is a utility question, not a hardware one.
"How do I do it without a transfer switch?"
This is one of the most searched questions on the subject, and it deserves its answer before any explanation.
The question is usually asked for one of two reasons, and they lead to opposite places. If a transfer switch is too expensive or too rigid, the interlock is the answer, and it is a proper answer rather than a compromise.
If the goal is to avoid an electrician altogether by pushing power backwards through a socket, that is not a lower rung on the same ladder. It is the next section.
Backfeeding a dryer outlet is a different act, not a cheaper one
The double-male cord has a nickname that has done more harm than good, because "suicide cord" sounds like folklore and folklore is easy to dismiss. The specifics are better than the nickname.
What the arrangement lacks is listed, mechanically enforced source isolation. Nothing in it stops the generator and the utility from being connected at the same time. Turning the main breaker off by hand is a procedure, and the code asks for equipment.
The cord itself carries a separate and simpler hazard. Once one end is energised, the pins on the other end are live and exposed. CPSC has recalled male-to-male cords on exactly that basis.
The consequence is documented rather than theoretical. OSHA recorded a June 2020 incident in which a homeowner started a generator and backfeed shocked a lineworker on poles believed to be de-energised, sending him to hospital. A NIOSH investigation documents a lineman killed on a line energised by portable generator backfeed.
Those are two separate agencies recording the same failure mode. The person at risk is frequently not the one who made the decision.
The compatibility checks most guides skip
Assume you have chosen an interlock or a transfer switch. Three things decide whether the installation works, and none of them appears on most of the pages ranking for this search.
The neutral bond
Portable generators ship in two configurations. Some bond the neutral to the frame; some leave it floating. Which one you have decides whether it can be connected to your transfer equipment as it stands.
If the transfer equipment switches only the hot conductors, the generator neutral stays connected to the service neutral, the generator is not separately derived, and a second neutral-to-ground bond does not belong there. Two bonds put normal neutral current on grounding conductors and can trip the generator's own GFCI receptacles.
If the equipment switches the neutral as well, the generator becomes a separately derived source and normally keeps its bond.
The permit
There is no national rule, because the authority having jurisdiction decides. The pattern in local guidance is consistent, though, and it splits on the same line this article opened with.
Miami-Dade County requires an electrical permit when a portable generator is connected to building circuits, and does not require one for direct cord use. Humboldt County's checklist states that portable generators require permitting of the transfer switch only.
In other words, owning the generator triggers nothing. Modifying the panel triggers the permit and the inspection.
The rest of the compatibility list
Voltage and receptacle configuration, whether the generator's output matches the inlet and cord you plan to buy, GFCI behaviour on the generator's own receptacles, and whether your panel is on the interlock manufacturer's listed models. An electrician will check these before quoting. Checking them yourself first makes the quote faster.
What it costs, and why the published numbers disagree
There is no authoritative national dataset for this work in 2026, and pretending otherwise is how most pages on this subject answer the question. What exists is commercial estimating sources, and they contradict each other.
For an interlock and inlet, one contractor-pricing vendor models $450 to $900, built from two to four labour hours plus $200 to $450 of materials. For a manual transfer switch, the same source models $900 to $1,900, while Angi reports $400 to $1,300 installed.
Those two ranges for the same job barely overlap. Treat all of them as budgeting estimates rather than prices, and get two local quotes, because the number that matters is the one on your quote.
Outage day: the order to do things in
The sequence matters more than any single step, because most of the ways this goes wrong are ordering mistakes.
- 1
Place and start it outside
20 feet out, exhaust pointed away from windows, doors and vents. Start it with no load connected and let it settle.
- 2
Open the main breaker
With an interlock, the plate will not let the generator breaker move until the main is off. That is the interlock doing its job, not a fault.
- 3
Turn off the branch breakers you are not backing up
Electric range, water heater, dryer, air conditioning. Starting with everything on is how a correctly sized generator gets blamed for stalling.
- 4
Connect the cord, then close the generator breaker
Cord to the inlet first, then energise. Never the other way round, which leaves a live end in your hand.
- 5
Bring circuits back one at a time
Largest motor load first, while there is the most headroom for its starting surge. Then the rest, watching the engine note.
- 6
Reverse it exactly when utility power returns
Branch breakers off, generator breaker off, disconnect the cord, then the main back on. Let the engine cool before refuelling.
Two habits are worth adding to the list. Keep a working carbon monoxide alarm on every level of the house, because it is the only thing in the whole system that watches the failure the wiring cannot see. And let the engine cool before refuelling it.
What not to plug into a generator
The honest version of this answer is narrower than the usual list, because there is no evidence-based blacklist of appliances.
The real test is whether the machine supplies the voltage, frequency and power quality the equipment's own manufacturer requires. Honda's guidance is the useful framing: voltage fluctuation can shut equipment down or damage it, AVR-regulated units hold voltage steadier, and inverter generators give the cleanest output for sensitive electronics.
Do
- Match the load to the receptacle and cord rating, not to the generator's total.
- Use an inverter generator, or an inverter, for anything with a computer in it.
- Read the manual for medical equipment before assuming a generator will run it.
- Treat power quality as a specification, not a feeling about the brand.
Don't
- Plug the generator into a wall receptacle or a dryer outlet, ever.
- Exceed the receptacle rating because the generator has capacity spare.
- Assume a well pump or central air is banned; they are hardwired, not forbidden.
- Use a damaged or indoor-only cord because the run is short.
Well pumps and central air are the two loads people believe are prohibited. They are not. They are hardwired, which means they need a panel connection rather than a cord, and they draw a large starting surge, which means they need a machine sized for it.
Where the sizing question comes back
The connection method you choose changes what you are sizing for, which is why this decision comes before the arithmetic rather than after it.
A cords-only setup is sized to a short list of appliances you can name. A panel connection adds the hardwired loads, and the largest of those usually brings the biggest starting surge in the house with it.
At the generator size calculator's defaults, 3,000 running watts plus a 2,200-watt surge gives 5,200 watts of peak demand, and the 20% headroom lands the recommendation at 6,240 watts, which is a 7,000 to 7,500-watt machine. Adding a well pump to that list moves the number, not the method.
Common mistakes to avoid
- Buying the inlet and thinking it is the safety device. The inlet is a socket. The interlock or the transfer switch is the part the code is asking for.
- Buying an interlock that fits but is not listed for your panel. Physical fit is not listing, and this is the usual reason a tidy installation fails inspection.
- Running the generator in an open garage. CPSC names garages explicitly, doors open included.
- Treating a CO shutoff feature as permission to move it closer. It is a second layer under the 20 feet, not a replacement for it.
- Closing the generator breaker before the cord is connected. That puts a live end in your hand.
- Assuming the neutral bond must come out. It depends on whether your transfer equipment switches the neutral, and getting it backwards causes nuisance GFCI trips at best.
- Taking a single published installation price as the market rate. The public figures for the same job disagree by a factor of two.