A manual transfer switch is a separate box that moves selected circuits to the generator. An interlock kit is a mechanical slide on your main panel that keeps the main breaker and a generator breaker from being on together. Both need a power inlet box and a licensed electrician.
The two approaches
| Manual transfer switch | Interlock kit | |
|---|---|---|
| What it is | A separate switch box wired to selected circuits | A mechanical slide fitted to your main breaker panel |
| Which circuits get power | Only the circuits wired to the switch (for example 6 or 10) | Any circuit on the panel, within the generator's watts |
| Panel fit | Works with most panels; wiring by the electrician | Specific to your panel's brand and model |
| Typical advantage | Chosen circuits are protected from overload by design | Lower hardware cost; flexible circuits |
| Typical risk | Fewer circuits; installation cost | Easy to overload a generator by switching on too much |
| Installer | Licensed electrician, with permit and inspection | Licensed electrician, where code allows |
Both usually connect to the generator through a power inlet box mounted outside and a generator cord of matching amperage.
What must match
- Amperage through the whole chain: generator outlet, cord, inlet box and switch. 30 A and 50 A are the common ratings.
- Connector type at each end, such as L14-30 or 14-50.
- Generator watts against the circuits you choose; watts = amps × volts.
- Panel brand and model for an interlock kit.
Browse transfer switches, interlock kits, inlet boxes and cords and use the matrix.
Why an electrician
Some battery systems and home-backup kits use the maker's own transfer hardware; the same rule applies — a licensed electrician installs it.
Questions readers ask
Can I install an interlock kit myself?
Do I need a transfer switch for a power station?
Figures marked as Wattstanding calculations show their working; product figures come from the sources on each product page. How we work