How do I connect a portable power station to my home's electrical panel?

Why this needs transfer equipment at all: backfeed

A power station's inverter makes the same 120/240 V electricity as the grid. If it is connected to house wiring while the house is still tied to the utility, that power can flow out through your meter. OSHA's portable generator guidance is blunt: never attach a generator directly to a building's electrical system "unless a qualified electrician has properly installed the generator with a transfer switch," because doing so "can energize wiring systems for great distances" and creates "a risk of electrocution for utility workers." A federal worker-safety fact sheet on power outages explains the mechanism. Current fed into a household circuit can travel back to the grid and "increase in voltage" on the way, which is how a small backup source becomes a hazard on a line crew's wire. That rules out the male-to-male cord into a wall outlet entirely: it bypasses any transfer equipment.

Ford's home-backup instructions for its trucks say the same thing in consumer language. Never connect vehicle power outlets to a premises "unless using proper equipment and only after obtaining any necessary approvals from your utility," because the alternative "may create backfeed to utility lines."

What the electrical code requires (NEC Article 702)

A home backup source you choose to install is an optional standby system under NEC Article 702. As summarized by code educator Mike Holt, the core rules are:

• Transfer equipment is required to connect the backup source to premises wiring (702.5(A)). It must be listed and installed to prevent the inadvertent interconnection of all sources of supply.
• Size for what you'll run at once. With manual transfer, the system must be sized to supply all the loads intended to operate at one time (702.4(A)).
• A warning sign at the power inlet must state what type of generator may be connected to it (702.7(C)).

Your state may enforce a different NEC edition with local amendments, which is one more reason the permit office and a licensed electrician should be involved.

Option 1: a manual transfer switch

A manual transfer switch is a small panel mounted next to your main panel. A handful of circuits you choose, such as the fridge, furnace blower, some lights and a few outlets, are rewired through it. Each has a switch that selects LINE (grid) or GEN (backup). Reliance Controls, a common brand, explains why this is safe in its manual: "the double-throw action of these switches prevents feeding generator power to the utility and, conversely, prevents feeding utility power to the generator." Transfer switches like this are evaluated to UL 1008, the standard for transfer switch equipment.

• Good fit if: you want a short, fixed list of essential circuits and a power station or generator that can't run the whole house anyway.
• Trade-off: you choose circuits once at install time. Adding another later means another visit from the electrician.

Option 2: an interlock kit on your main panel

An interlock kit is a sliding plate on the main panel's deadfront. It physically prevents the main breaker and a dedicated backup breaker from being on at the same time. According to UL's guidance published in IAEI Magazine, panelboard interlock kits are recognized "transfer equipment" under NEC 702.5. They are evaluated as part of the panelboard (UL 67), and field-installed kits are covered when the panel's markings identify that kit for use with it. In practice that means the kit has to be the one made for your panel's brand and model, not a generic plate.

• Good fit if: you want to be able to pick any circuit during an outage.
• Trade-off: every circuit in the panel is available, so you have to manage the load yourself. Turn off big loads before switching over, and stay under the power station's continuous rating.

Option 3: the power station maker's smart panel

Several large power stations have a matching panel that does the transfer automatically and talks to the battery through the maker's own cable. These are brand-specific. None of them turns a different brand's power station into a home backup system.

Smart panels cost more than a manual switch, but they remove the two mistakes people make most often with manual setups: forgetting to switch back, and plugging in the wrong cord or adapter.

The inlet box and cord

With a manual transfer switch or an interlock, the power station never comes inside. An electrician mounts a power inlet (a male receptacle in a weatherproof box) on an outside wall. A cord runs from the power station's outlet to that inlet. The inlet's shape tells you what the system expects:

The cord must be rated for the outlet, and the inlet must carry the 702.7(C) sign saying what can be plugged into it.

The TT-30-to-L14-30 adapter trap

This is where many DIY setups go wrong. The power station has a TT-30 outlet, the inlet is an L14-30, and an adapter seems to solve it. It doesn't, at least not without trade-offs you need to understand.

• Unbridged adapter: a TT-30 has only one hot. An adapter that wires it straight through feeds only one of the L14-30's two hots, so every transfer-switch circuit on the other leg stays dead.
• Bridged adapter: these are sold specifically for this job. AC Works, for example, markets a TT-30P-to-L14-30R adapter with "two hots bridged" and a maximum operating power of 3,750 W. It energizes both legs, but from the same 120 V source. 240 V loads such as a well pump or electric water heater won't run.
• The neutral problem: older and some newer homes have multi-wire branch circuits, where two 120 V circuits share one neutral wire. The setup depends on the two circuits being on opposite legs, so their neutral currents cancel. Reliance's transfer switch manual requires both circuits of a multi-wire branch to be connected to opposing legs with a handle tie, and warns that "failure to properly install a multi-wire branch circuit could result in overloading the neutral wire." A bridged adapter defeats that design: the two currents add instead of cancel.

If your power station also has a true 120/240 V output, using that is the cleaner route. If it only has 120 V, tell your electrician up front. They can identify any shared-neutral circuits and plan the transfer equipment around a 120 V-only source, rather than leaving you with an adapter workaround.

Sizing: what the power station can actually run

Under 702.4(A) the system has to cover what you'll run at once, and in practice the power station's continuous output is the ceiling. As a worked example, 3,600 W at 120 V is 30 A total (3,600 ÷ 120), shared by every backed-up circuit. A well pump, a fridge and a microwave starting together can exceed that, and it's the reason you pick circuits deliberately. Check the continuous and surge ratings in your power station's manual, not the battery capacity in kWh. The kWh number only tells you how long it lasts.

Who should do this work

All three options involve working inside or beside the main panel, so this is a job for a licensed electrician and, in most places, a permit and inspection. That isn't caution for its own sake: OSHA, Reliance, EcoFlow and Jackery all say so in their own documents. EcoFlow's manual has the installer pulling the permit. Reliance's says installation "must be performed by a qualified electrician in compliance with all applicable electrical codes." Treat any video showing a different shortcut as a red flag.

If your backup source is a gas generator rather than a battery, the connection rules are the same but carbon monoxide becomes the bigger risk. See home battery vs generator for the CDC and CPSC placement rules. If you drive an EV, some can power a house too; see can an EV power your house.