INTERLOCK KIT
Mechanical interlock at the panel for portable generator backfeed. Code-compliant, listed for the panel brand, faster and cheaper than a transfer switch.
Keil Electric installs generator interlock kits across San Diego County and the Austin metro for homeowners who want to power circuits from a portable generator without a transfer switch. We install panel-brand-listed interlock kits, the inlet receptacle, and the backfeed breaker, all to code.
Same scope on either side. Pick the shop that covers your area and we will route you to the right crew.
An interlock kit is a sliding metal plate that mechanically prevents the main breaker and the generator backfeed breaker from being on simultaneously. The customer turns off the main, slides the plate, turns on the generator breaker, and powers selected circuits from the portable generator.
Interlock kits are listed for specific panel brands and series (Square D QO, Eaton CH, GE THQL, Siemens). Cross-brand or generic kits are not code-compliant and can void the panel listing. We use only panel-listed kits.
The generator inlet is the weatherproof outlet on the exterior of the home where the generator cord plugs in. Common is the 30A L14-30 (3,600W) or 50A 14-50 (7,200W) configuration. We site the inlet for accessibility, run cable to the panel, and terminate at the backfeed breaker.
Most jurisdictions require a permit for generator interlock installs. We pull it, install per code, and schedule any inspection. The customer leaves with documented, code-compliant backfeed capability.
We verify the panel brand and series, confirm a listed interlock kit is available, and inspect for available breaker space.
Walk the exterior, pick the inlet location, and confirm the cable route to the panel.
Inlet receptacle, cable run, backfeed breaker, and interlock kit installed.
Test the interlock function, confirm no simultaneous-on condition, document the install for the customer.
Not every job requires a permit. When the local AHJ requires one, we pull it, schedule the inspection, and stay with the job until it passes. No paperwork on you.
Written warranty: 5-year on outlets, fixtures, and EV chargers; 10-year on wire and breakers; lifetime on panelboxes and surge protection. Parts and labor. Transfers with the home.
Backfeeding a generator into a panel without a code-compliant interlock is illegal and dangerous. The interlock physically prevents the main breaker and the generator breaker from being on at the same time, which protects utility lineworkers from backfed power.
Real work from our San Diego and Austin shops. Same standards, same warranty, every job.
For generator interlock switch installation, here's the honest comparison. We'd tell you the same thing if we weren't trying to win the job.
Most generator interlock switch installation calls start when the homeowner is planning ahead: a renovation, an addition, an EV charger, a generator, a panel upgrade, or any project where the existing electrical needs to be sized correctly for the new load. The earlier we walk the property, the cleaner the project sequencing. Bringing us in before the drywall closes saves rework. Bringing us in before the contract is signed with the GC saves scope confusion. We are happy to walk a property at the planning stage even if the install is still months out.
A walk of the property with attention to the panel (age, capacity, available breaker space), conduit accessibility, attic / crawlspace conditions, and the load picture (current loads + planned future loads). For installs that touch the service drop, we factor utility coordination from the start. The estimate we leave with is fixed for the scope as walked. Change orders only happen for genuinely new findings during the work, you hear about them before we proceed.
Generator interlock installation is the budget-conscious alternative to a full transfer switch. The customer keeps a portable generator, runs an extension cord into the inlet receptacle, manually transfers the panel via the interlock plate, and powers select circuits during an outage. The install is faster and cheaper than a transfer switch, and the operation is manual rather than automatic.
A transfer switch is automatic or manual, switches between utility and generator, and is a separate piece of equipment. An interlock kit is a manual mechanical device installed at the panel that physically prevents both sources from being on at once. Interlocks are cheaper but require manual operation.
Most modern panels (Square D QO, Eaton CH, GE THQL, Siemens) have listed interlock kits available. Older panels or unusual brands sometimes do not. We confirm compatibility before quoting.
Depends on what you want to power. A 3,600W generator runs essential refrigeration, lighting, and small loads. A 7,200W generator runs more, including a window AC or microwave. Sizing depends on what you actually need during an outage.
Yes. Backfeeding through a "suicide cord" or any setup that does not include a listed interlock or transfer switch is a code violation and a serious safety risk to utility lineworkers. We will not do those installs.
Total cost includes the interlock kit, the backfeed breaker, the inlet receptacle, cable, and labor. We quote in writing after the panel check.
A licensed electrician confirms panel compatibility, kit availability, and inlet location, then writes the install in fixed-price terms.
