Three ways to connect a portable generator to your house. Two are legal in South Carolina. One is cheaper, faster, and works with any circuit. Inlet box + interlock, $1,197–$1,497 all in. Permit pulled, inspection included, done in a day.
Get my quoteWhen a storm takes the grid down, you have three options for getting power from your portable generator into your house. They differ on cost, safety, flexibility, and whether they'll pass an inspector.
A weatherproof inlet on your exterior wall feeds a new breaker in your main panel. A mechanical interlock slides between the main breaker and the generator breaker, making it physically impossible for both to be on at once (no back-feed risk). Every circuit in your panel is available — you just flip breakers based on what the generator can handle.
A separate sub-panel wired alongside your main. During install you pick 6–10 circuits to move under the transfer switch. When power goes out you plug the generator in, flip the transfer switch to generator mode, and those pre-selected circuits run. Un-selected circuits stay dead until the grid is back.
Run the generator outside, drop heavy-gauge extension cords through a window or door, plug appliances directly into the generator. No electrician, no permit — but you're limited to what you can plug into cords.
| Inlet + Interlock | Transfer Switch | Extension Cords | |
|---|---|---|---|
| Installed cost | $1,197–$1,497 | $1,800–$2,600 | $0 |
| Covers 240V loads | Yes | Yes (if selected) | No |
| Circuit flexibility | Any circuit | Pre-selected only | Corded only |
| Permit + inspection | Included | Included | Not required · none |
| Back-feed safety | Mechanical interlock | Physical switch | Dangerous if misused |
| Install time | 1 day | 1 day | 5 min |
Inlet + interlock is the right call if you want the lowest-cost code-compliant solution and you're comfortable flipping a few breakers during an outage.
Transfer switch is worth the upcharge if your panel is 40+ years old, already full, or you want a no-thinking pre-selected circuit set that non-technical family members can operate.
Extension cords are a last resort. Fine for a fridge and a lamp during a 4-hour outage, but not a real backup strategy.
Can I just run extension cords from my generator to appliances? Yes, but it's limited. Extension cords only power what you plug directly into them — fridge, lamps, one device at a time. You can't run hardwired items like well pumps, furnaces, or 240V water heaters. Never back-feed a dryer outlet — it's illegal and will kill a lineman working on the downed line.
What's the difference between a transfer switch and an interlock kit? A transfer switch is a separate sub-panel with 6–10 pre-selected circuits. An interlock is a mechanical slide inside your main panel — any circuit stays available, you just manage breakers. Interlocks are cheaper and more flexible; transfer switches are set-and-forget UL-listed systems.
How long does the install take? One day on-site, 3–5 hours. Full lead time including the permit is usually 1–2 weeks from quote to done.
Do I need a permit? Yes. Every jurisdiction we work in (Greenville, Spartanburg, Pickens counties) requires an electrical permit any time a panel is modified. We pull the permit, pay the fee, and stand for the inspection. Skipping it voids your homeowner's insurance if a fire ever involves the panel.
What size generator do I need? For basics (fridge, lights, WiFi, gas furnace blower) a 5,000–7,500W portable on a 30A inlet is plenty. For well pumps, electric water heater on reduced draw, or central A/C on smaller units, step up to a 10,000W+ portable on a 50A inlet.
Do you service my area? Yes — we cover all of Greenville, Spartanburg, and Pickens counties. See the 13 cities we serve.
Text us your address and generator model — we'll confirm the right inlet size and text you a locked-in quote.
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