Do I need a permit to install a standby generator?
Usually needs a permit
A permanently installed generator is two permitted trades at once — the electrical connection and the fuel supply — and the transfer switch is the part that is never optional.
What changes the answer
- Permanently installed standby generator — an electrical permit, plus a gas permit where it runs on natural gas or propane
- A transfer switch or an approved interlock is required, so the generator can never be connected to the utility at the same time
- Placement is regulated: clearance from the building, from openable windows and from the meter, per the manufacturer's listing and the code
- A portable generator with extension cords to appliances — not an installation, and generally not permitted work
- Backfeeding through a dryer or range outlet is not a legal method anywhere, whatever it is called online
These thresholds come from the model code and are commonly amended locally, which is usually where people get caught.
Why it matters
The transfer switch exists to protect people you will never meet. A generator backfed into house wiring while the utility is down energises the service drop and the transformer steps that voltage back up on the line outside — which is a lethal hazard to the line workers restoring your power. The second risk is carbon monoxide from exhaust placed too near a window, which kills people every storm season.
Confirm the requirement with the authority that would issue the permit before deciding.
The version of this people actually ask
Do I need a permit for a portable generator?
Not for owning or running one on extension cords — no installation has taken place. It changes entirely if you connect it to the house wiring: doing that legally means an inlet and either a transfer switch or a listed panel interlock, and that is permitted electrical work. Running a portable generator is otherwise a carbon monoxide question rather than a permit one, and the answer is that it belongs well away from the building and never in a garage, open door or not.
Do I need a permit for a transfer switch or an interlock kit?
Yes, and this is the item most worth permitting even where enforcement is unlikely. An interlock is a mechanical device that makes it physically impossible to close the generator breaker and the main at the same time; a transfer switch does it automatically. Both are cheap, both are inspected quickly, and both exist to prevent energising a line that someone else believes is dead.
Where can a standby generator be placed?
Governed by the manufacturer's listed clearances and by code requirements on separation from the building and from openings — the concern being exhaust near a window, a door or an air intake, and combustion air for the unit. Placement is also frequently constrained by things outside the building code: setbacks, noise ordinances, and in many jurisdictions distance from the gas meter and the property line.
Do I need a gas permit for a natural gas generator?
Generally yes, in addition to the electrical one. The generator is a substantial gas appliance and the existing supply frequently cannot serve it alongside the furnace and the water heater at once — so the job commonly includes upsizing the line, and sometimes the meter. The finished line has to be pressure tested, which is a large part of what the inspection is for.
This is the typical rule, not your answer
This is the typical rule in the United States and not a decision about your property — permitting is run by more than 22,000 separate authorities and any of them can amend the code it adopts, so confirm with your local building department before you start. Put a ZIP in to see what applies in that state, and how to reach the office that decides.
Not in the IRC R105.2 exemptions. Optional standby systems are covered by NEC Article 702, which requires transfer equipment preventing inadvertent interconnection with the utility; the fuel connection falls under IRC Chapter 24 / the International Fuel Gas Code, and appliance clearances under IRC M1307.
Other projects
- Build a deckA permit is usually required once a deck is more than 200 square feet, more than 30 inches above grade, serves an exit door, or is attached to the house.
- Put up a fenceFences under 7 feet are typically exempt from a building permit — but height limits, corner-visibility rules and pool-barrier requirements are set locally and catch people constantly.
- Add a shed or small outbuildingOne-story detached sheds are typically exempt up to 200 square feet under the residential code — but the number people quote is 120, and both are right depending on which code your jurisdiction adopted.
- Replace a water heaterReplacing a water heater almost always requires a permit, even though it is routinely done without one.
- Remove or open up an interior wallIf the wall is load-bearing, a permit and engineered drawings are required. If you are not certain whether it is load-bearing, assume it is.
- Upgrade or replace an electrical panelPanel and service work always requires a permit, and in most places must be done by a licensed electrician.