Portable gen, no transfer switch? Don't backfeed.
Portable generators must connect through a transfer switch or interlock kit — never through an outlet (which backfeeds and can kill PG&E workers). Emergency install possible.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Portable generator emergency hookup options: (1) Interlock kit on existing panel — most cost-effective ($600-$1,200 install), allows selected circuits to be powered from generator via mechanical interlock that prevents simultaneous utility+generator. (2) Manual transfer switch — purpose-built switch ($1,200-$2,500 install) for 6-10 selected circuits. (3) Whole-house transfer switch — full transfer ($2,000-$4,000 install) for entire panel. (4) NEVER: backfeeding through a dryer outlet or any outlet — illegal, dangerous, can electrocute PG&E lineworkers. Emergency install possible in some cases; we explain trade-offs.
01Why backfeeding kills.
When you plug a portable generator into a dryer outlet (the most commonly suggested wrong way), or any outlet, while utility power is off, the generator energizes your home's wiring. That wiring is connected at the panel to the service entrance, which is connected to the utility transformer, which is connected to the distribution lines. PG&E lineworkers expect those lines to be de-energized during the outage — that's why they're working on them. Backfeeding from a portable generator energizes the line they're touching. People have died from this.
Beyond the lineworker risk, backfeeding creates other problems: when utility power returns, your generator and the utility are out of sync, producing a destructive surge that can damage the generator, panel, and connected equipment. There's no overcurrent protection on the backfed connection. The 'easy' solution of plugging a generator into a dryer outlet creates multiple safety failures simultaneously. Don't do it, regardless of what YouTube tutorials suggest.
02Proper hookup options compared.
Interlock kit — most cost-effective
Mechanical plate installed on the panel that physically prevents the main breaker and a designated generator inlet breaker from being on simultaneously. You connect generator to an inlet receptacle on the exterior, flip the main breaker off, then turn on the generator inlet breaker, then selectively turn on which circuits you want powered from generator. Cost: $600-$1,200 install. Requires panel that's interlock-compatible (most common panels are; some aren't).
Manual transfer switch — dedicated circuits
Separate transfer switch installed alongside panel, with 6-10 individually transferable circuits selected during install. Each circuit can be set to UTILITY, OFF, or GEN. More expensive but cleaner installation, easier operation. Cost: $1,200-$2,500 typical.
Whole-house transfer switch — full panel
Transfer switch handles entire panel. Generator must be sized for total load (or you manage load manually during use). Cost: $2,000-$4,000 typical. Best for owners planning to upgrade to standby generator later (transfer switch is reusable for automatic transfer when generator is upgraded).
03Emergency vs scheduled install.
Emergency install during active outage: possible but with caveats. The work itself takes 3-6 hours typically (interlock kit faster, transfer switch longer). Work requires the panel to be de-energized during install — which is already true if utility power is out, but means your portable generator can't be running during the install either. Plan: schedule install during a quiet period of the outage (not the first hours when you're triaging more urgent needs).
Better: schedule install before outage season. October pre-AR-season is ideal. You buy the portable generator (or already have one), we install the proper connection point, and when the next outage hits you're ready immediately. Cost is the same; convenience is significantly better. Most homeowners who experience one outage scramble end up doing this within a few months.
Common questions.
What size portable generator do I need?
Depends on which circuits you want to power and your usage. Common Marin scenario: refrigerator + freezer + a few lights + furnace blower + electronics = 3,500-5,500 watts typical (need a 5,000-6,500W generator to allow startup surges). Adding well pump, electric stove, AC, or EV charging increases requirements. We help size during consultation. Note: portable generators are loud — neighbors will hear it during multi-day outages.
Can I just run an extension cord from the generator to my refrigerator?
Yes, and that's a legitimate option that requires no electrical work — heavy-gauge extension cords from generator outdoors through a window to powered appliances. Limitations: only powers what you can reach with the cord, requires open window or door (security and weather issues), can't power hardwired equipment (furnace blower, well pump). Many Marin homeowners use cord-only approach for short outages and transfer switch for serious outage preparedness.
Is interlock kit really safe?
Yes when properly installed. The mechanical interlock physically prevents both breakers from being on at the same time — no software, no failure modes, just metal. Code-compliant. Inspected. Used by hundreds of thousands of homes. The risk with portable generators is operator error (backfeeding through outlets) not the interlock approach. Interlock + portable generator is widely accepted as proper hookup.
Can I do this myself if I'm handy?
Service entrance and panel modification is licensed electrician scope in California. Interlock kit and transfer switch installation both involve panel work, permit, and inspection in Marin County. DIY isn't a legal option for this scope. Generator selection, fuel management, and operation are owner scope; the electrical interface is electrician scope.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
Emergency response across Marin County.
Same-day dispatch for safety scenarios. Typical on-site time 1-3 hours weekday, 1-4 hours after-hours.