Extension cords work for a fridge and a lamp. But some of the things you most need in an outage (a furnace blower, a 240 V well pump, hard-wired lights) can't be plugged into a cord. To power them, your generator or large power station has to connect to your home's electrical panel, and that has to be done safely.
This guide explains the options in plain language so you can have an informed conversation with a licensed electrician, who should handle the installation and any required permit and inspection. It is not a how-to for doing the wiring yourself.
Why you can't just plug into an outlet
Every safe connection does the same job: it makes it physically impossible for your backup source and the utility to feed your panel at the same time. FEMA's generator safety guidance advises using a qualified electrician to install the appropriate equipment; we recommend a licensed electrician who pulls the required permit in your area.
The main options
| Option | How it works | Good for |
|---|---|---|
| Manual transfer switch | A small sub-panel next to your main panel with switches for pre-selected circuits (e.g. fridge, furnace, well pump). You flip each one from "line" to "generator". | Choosing exactly which circuits get backup power |
| Interlock kit + inlet box | A plate on the main panel that prevents the main breaker and a dedicated generator breaker from being on together. The generator plugs into an outdoor inlet box. | Flexibility to run any circuit, as long as you manage the load |
| Automatic transfer switch (ATS) | Detects an outage and switches over automatically. Usually paired with a permanently installed standby generator or home battery system. | Whole-home systems; people who can't be home to switch over |
| Power-station home panels | Some large power station makers sell their own transfer panels for 120/240 V units. | Big battery systems like the EcoFlow DELTA Pro 3 or Anker SOLIX F3800 Plus |
Which is right depends on your panel, local code and what you want to run. Your electrician will tell you what's allowed where you live.
Matching your generator's outlet
Your generator connects to the inlet box with a cord that matches one of its locking outlets. The outlet decides whether you can feed 240 V circuits.
| Outlet | Voltage | What it can feed | Examples in our guides |
|---|---|---|---|
| L14-30R | 120/240 V, 30 A | Both sides of the panel, including 240 V well pumps | Generac GP7500E, Westinghouse WGen9500DFc, Champion 201508, EcoFlow DELTA Pro 3, Anker SOLIX F3800 Plus |
| 14-50R | 120/240 V, 50 A | Larger 240 V connections (check inlet and cord rating) | Westinghouse WGen9500DFc, Champion 201508 |
| L5-30R | 120 V, 30 A | 120 V circuits only | Champion 201296 |
| TT-30R | 120 V, 30 A (RV) | Designed for RVs; not a standard home transfer connection | Champion 201321 and 201296 |
If you need a 240 V well pump, choose a generator or station with an L14-30R (or 14-50R) outlet. See best dual-fuel generators and the whole-home picks in best portable power stations.
Planning which circuits to back up
- 01List your must-haves: fridge, freezer, furnace blower, well or sump pump, a few lights, router and outlets for charging.
- 02Find each one's running and starting watts. The sizing quiz adds them up and shows the surge you need.
- 03Make sure your generator or station's running watts exceed the total with ~20% margin, and its starting watts cover the biggest motor.
- 04Give your electrician the list and your generator's outlet type and wattage.
- 05Label the circuits on the transfer switch or panel so anyone in the house can follow the procedure.
Questions to ask your electrician
- Is a manual transfer switch or an interlock kit allowed for my panel, and which do you recommend?
- Does this installation need a permit and inspection here?
- Where should the inlet box go so the generator can sit 20+ ft from the house with the cord length I'll need?
- What cord gauge and length do I need for my generator's outlet and wattage?
- Can you walk me through the switch-over and switch-back steps and label everything?
The basic switch-over sequence
Your electrician should give you the exact steps for your system. In general: place the generator outdoors at least 20 ft from the house, start it, let it stabilize, connect the cord to the inlet, then switch your transfer switch or interlock to generator and turn on circuits one at a time, largest motor first. When utility power returns, reverse the order before shutting the generator down.
When to go whole-home
If you want central air, electric heat or automatic switchover, you're in standby-generator or home-battery territory. Those are installed systems with permits and costs that depend on your home, so we don't publish prices. The results page of our sizing quiz lets you request a local installer contact.
Not sure what size you need? Add up your own appliances in the free sizing quiz. It shows the math.
Take the sizing quizFAQ
- Do I need a transfer switch for a portable generator?
- Only if you want to power hard-wired circuits (furnace, well pump, hard-wired lights). For plug-in appliances, heavy-duty outdoor extension cords are fine. Never plug a generator into a wall outlet.
- Can I install an interlock kit myself?
- We recommend a licensed electrician. It involves working inside your main panel, and most jurisdictions require a permit. FEMA advises using a qualified electrician to install the appropriate equipment.
- What's the difference between an interlock and a transfer switch?
- A transfer switch is a separate sub-panel with dedicated switches for selected circuits. An interlock is a mechanical plate on your main panel that prevents the main and generator breakers from being on at the same time, letting you choose circuits from the main panel.
- Can a power station connect to a transfer switch?
- Large 120/240 V stations such as the EcoFlow DELTA Pro 3 and Anker SOLIX F3800 Plus have L14-30R outlets designed for this. Smaller 120 V stations are best used with extension cords.
Sources
- [1]CPSC Safety Alert: Portable Generator Hazards (Publication 5123) (October 2021)
- [2]FEMA fact sheet: Be Safe When Using a Portable Generator (2017)
- [3]CPSC: safety tips to prevent carbon monoxide poisoning and fires during winter storms (December 12, 2025)
- [4]Champion Power Equipment: Generator Wattage Chart (accessed October 27, 2026)
Related guides
- Generator Safety: How to Prevent Carbon Monoxide Poisoning →The CDC and CPSC rules: placement, CO alarms, backfeeding, fuel and symptoms to know.
- Best Dual-Fuel Generators for Home Backup (2026) →Five gasoline + propane picks with CO shutoff, from fridge-and-sump size to 240 V transfer-switch size.
- Best Portable Power Stations for Power Outages (2026) →Six LiFePO4 picks from phone-and-CPAP size to whole-home scale, with runtime math for each.
- Power Station vs. Generator: Runtime, Watts, Safety and Cost Compared →Side-by-side comparison of batteries and fuel generators, and why many homes end up with both.
Planning the rest of your outage kit? Visit the Outage prep hub: PowerLockdown or The Blackout Kit on PowerLockdown.