Backup power
Standby generator installs (natural gas or LP) and portable-generator interlock kits. Outage goal first, equipment selection second.
Backup power work at Keil Electric covers whole home generator installation (natural gas or LP) and generator interlock switch installation for portable generators. Every project starts with the outage goal - which loads need to stay on, panel condition, and where the generator will sit - before specifying equipment.
Same scope on either side. Pick the shop that covers your area and we will route you to the right crew.
Generator and Backup Power covers a few different jobs that look similar from the outside but are quite different in scope, cost, and timeline. Here is the version that helps you walk into the call already pointed at the right one. We will confirm or correct on the phone.
If you are planning the kind of work this covers, 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. Read the full generator interlock switch installation page.
If you are planning the kind of work this covers, Keil Electric installs whole-home standby generators across San Diego County and the Austin metro. Generac, Kohler, and Briggs & Stratton air-cooled units (typically 18-26kW). We size to actual load, coordinate the gas line and concrete pad, install the automatic transfer switch, and program the controller before commissioning. Read the full whole home generator installation page.
It is common to need more than one of these at once, especially on older homes or commercial buildings where one underlying issue surfaces in several places. We bundle the work under a single scope and a single permit when the project lines up that way, which usually saves time and money versus running each as a separate visit. If you are not sure which page fits, pick the closest one or call. We will sort it out.
Pick the job that matches what you need. Each one is a licensed install with the same written warranty as the rest of our work.
We size to NEC 220 demand factors, not square footage or "how big my neighbor went." The calc covers continuous loads, the largest motor load, and reasonable margin for inrush. Most residential installs land between 14kW and 22kW. Smaller homes with gas appliances can fit on 9kW. Larger or all-electric homes go 22kW or 26kW.
Natural gas is the default when service is available. LP is the right call when there is no gas service or when the homeowner wants fuel storage they control. Dual-fuel adds cost and rarely pays back in flexibility unless the fuel question is genuinely uncertain.
An ATS is hands-off and switches loads in seconds during an outage. A manual interlock costs less and is the right scope for portable generators where the homeowner is willing to roll out the unit and throw the switch. Both meet NEC 702.5 anti-back-feed requirements when installed correctly.
The pad has to be level, rated for the equipment weight, and meet NFPA 37 clearances (typically 5 feet from openings, 18 inches from the home for service access). We avoid AC condensers, pool equipment, and low overhangs. HOA review happens before pour where applicable.
Generator installs trigger both an electrical permit and a gas permit. We pull both, coordinate the gas-first inspection sequence, and meet any inspectors. The electrical inspection covers ATS, interconnect, bonding, and disconnect. The gas inspection covers pipe sizing per NFPA 54 and pressure testing.
We visit the property, walk through the loads the homeowner wants on during outages, photograph the panel and gas meter, and measure the gas pressure at the meter to confirm capacity for the proposed unit size.
We run the load calc with proper demand factors, recommend a kW rating with margin, and confirm whether the existing gas service can support the unit or needs a meter upgrade.
Based on size, fuel, and budget, we recommend a unit (Generac, Kohler, or Cummins are the common residential brands) and an ATS or interlock. The written quote separates generator, ATS, pad, gas work, electrical, permit, and inspection coordination.
When the local AHJ requires permits (electrical and gas), we pull them with the city. Permit requirements vary by district. We give the realistic timeline at quote so the calendar conversation happens before deposit.
The concrete pad cures while we wait for equipment delivery. Manufacturer lead times run 2-12 weeks depending on the unit. We sequence the pad pour to land near the equipment delivery window.
We connect the gas line and pressure-test it, install the ATS at the panel, run the generator interconnect, and bond the equipment to the grounding system. The home is off utility power for a portion of the day.
Gas inspector first, then electrical. After both sign off, we start the generator, run a transfer test (simulate an outage and watch the ATS switch), set the weekly exercise time with the homeowner, and walk through maintenance.
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.
Generator work has hard rules. Never run a portable generator inside any enclosed space (CO poisoning is fast and silent. NFPA 58 and CDC guidance both call this out). Never connect a portable generator to the home with a "suicide cord." Use a properly installed interlock or transfer switch. back-feeding into the utility lines can kill linemen working to restore power. Never refuel a hot generator. Never operate a generator in standing water or during heavy rain without weather-rated housing. Always keep the exhaust at least 20 feet from any window, door, or vent per CDC guidance. Schedule annual maintenance. generators that sit idle for years often fail to start when needed.
Real work from our San Diego and Austin shops. Same standards, same warranty, every job.
For generator and backup power, here's the honest comparison. We'd tell you the same thing if we weren't trying to win the job.
A whole home standby generator runs on natural gas or liquid propane, sits outside on a concrete pad, and starts automatically when utility power drops. The decision homeowners face isn’t usually “do I need backup power?” It’s “what gets backed up, for how long, and on what fuel?” We start every project there.
Standby generators are rated by kilowatts. A 9kW unit handles essential circuits like the refrigerator, sump pump, a few outlets, and lighting. A 14kW unit covers most circuits in a typical home including HVAC. 22kW and 26kW units handle larger homes or homes with heavier electrical loads. The wrong size produces three different failure modes. Undersized units shut down under peak load. Oversized units short-cycle and wear out the engine and alternator early. Units sized to instantaneous peak instead of NEC demand factors lock the homeowner into more fuel cost than necessary.
The math behind sizing comes from a real load calculation per NEC 220, the same calculation we use for service upgrades. We document the loads the homeowner wants on during outages, run the demand factors that account for what actually runs at the same time, and recommend a unit that covers the realistic peak with reasonable margin.
Sizing depends on the load list, not the home’s square footage. A 4,000 sq ft home with a gas furnace, gas water heater, and gas range needs less generator capacity than a 2,000 sq ft all-electric home with a heat pump and EV charger. We ask the homeowner three questions before specifying: which loads are critical during an outage, how long are the typical outages in this area, and what’s the budget for fuel.
From there the calc is straightforward. Continuous loads (refrigeration, well pump, medical equipment) plus the largest motor load (typically the AC compressor or heat pump) plus a margin for inrush. The result is the kW rating. We recommend a unit one size up from the calculated number when the homeowner wants headroom for future loads (an EV charger, a hot tub, an addition).
Natural gas is the easier path when the home already has gas service. The generator ties into the existing gas line, the fuel is essentially unlimited (the utility’s grid stays up during most local outages), and there’s no tank to maintain. The trade-off is that natural gas has lower BTU content than LP, so the same kW rating draws more fuel volume per hour, and gas pressure has to be high enough at the generator’s regulator (typically 5-7 inches WC for residential).
LP is the right call when there’s no natural gas service, when the home is in a rural area, or when the homeowner wants fuel storage they control. A 500-gallon LP tank can run a 22kW unit for several days at half load. The downsides are upfront tank cost, refill scheduling, and tank placement clearances per NFPA 58.
Some installs use dual-fuel generators that can switch between natural gas and LP. We recommend dual-fuel only when the fuel question is genuinely uncertain, since the added equipment cost rarely pays back in flexibility.
The transfer switch is the device that decides whether the home runs on utility power or generator power. An automatic transfer switch (ATS) does this in seconds, without homeowner intervention. The ATS senses the utility outage, signals the generator to start, waits for stable output, and switches the load over. When utility power returns, it reverses the process.
A manual interlock is the cheaper alternative for homes with portable generators. The interlock is a mechanical device on the panel that prevents the generator breaker and the main breaker from being on at the same time, which is what NEC 702.5 requires to keep the generator from back-feeding into the utility lines. The homeowner manually rolls out the portable generator, plugs it into an inlet, throws the interlock, and turns on the breakers for the loads they want powered.
For a whole home standby generator, the ATS is the standard. For homeowners who already own a portable generator and want safe back-feed, the interlock is the right scope. Both paths require permits and inspection.
The generator’s location is constrained by manufacturer specs and code clearances. Most residential standby units require minimum clearances of 5 feet from openings (windows, doors, vents) on all sides per NFPA 37, and minimum 18 inches from the side of the house for service access. The pad must be level, sized for the unit, and rated for the equipment weight.
Common locations are alongside the home in a side yard, behind the home in a fenced area, or on a corner with good airflow. We avoid spots near AC condensers (the generator’s exhaust temperature affects the AC’s efficiency), near pool equipment (clearance from chlorine vapor), and under low overhangs (manufacturer clearance to the top).
Generator installs require both an electrical permit and a gas permit in most jurisdictions. The electrical permit covers the ATS, the generator’s electrical interconnect, and the bonding. The gas permit covers the fuel line from the meter (or LP tank) to the generator regulator, including pressure testing.
The inspection sequence usually runs gas first, then electrical. When an inspection is required, the gas inspector verifies pipe sizing per NFPA 54, leak-tests the line, and signs off. When an inspection is required, the electrical inspector verifies the ATS installation, the generator interconnect, the bonding to the equipment grounding electrode, and the disconnect. We pull both permits and coordinate the inspections.
The install itself runs 2-4 days on site for a typical residential standby generator with an ATS. The longer drivers are equipment lead times (2-12 weeks depending on the manufacturer and the size. Generac, Kohler, and Cummins are the common residential brands), permit turnaround, and inspection scheduling. We tell the homeowner the realistic full timeline at quote so the decision happens with the calendar in mind.
The gas line is too small. Older homes have 3/4-inch gas service designed for a furnace, range, and water heater. Adding a 22kW generator can require upsizing the meter or running a larger line from the meter to the generator. We test the gas pressure during the site visit and flag the upsize as a separate scope.
The panel doesn’t have an open slot for the generator backfeed circuit, or the available slots are at the bottom of the panel where the ATS can’t physically connect cleanly. Sometimes the answer is a panel upgrade as a separate scope. Sometimes it’s an external sub-panel for the generator-fed loads.
The HOA has equipment-placement rules that the homeowner didn’t anticipate. Generators are loud at startup and during weekly exercise cycles (typically 15-30 minutes once a week). Some HOAs require visual screening, specific exercise time windows, or pre-approval of the equipment.
The home is in a flood zone. Generators in flood zones need to be elevated above the base flood elevation per local floodplain ordinance and FEMA guidance. The pad design changes, and so does the cost.
Plan for a power-down on install day. The ATS install requires the home to be off utility power for several hours while we make the connections. Critical equipment (medical, server, refrigerator with sensitive contents) needs a temporary plan.
The generator will exercise itself weekly. Most units run a 15-30 minute self-test once a week at a time the homeowner sets. Neighbors notice it the first week. We can move the exercise time and trim the runtime to reduce friction.
Keep up with maintenance. A whole home generator needs annual oil change, air filter, and spark plug service to hold its rated output. We can include a maintenance plan or hand off the schedule for the homeowner to manage themselves.
Fuel choice is one of the two biggest decisions in a generator install (sizing being the other). The right answer depends on what is available at the property and how long the unit needs to run during an outage.
If the property has a natural gas line and meter, natural gas is usually the default choice. Run time is unlimited as long as gas pressure holds at the meter, a key advantage during multi-day outages. The gas line capacity has to support the generator’s consumption rate plus any existing gas appliances (furnace, water heater, range, dryer). Most residential gas services support a 22-26 kW generator; some smaller services need an upgrade to the meter or service line.
NEC handles the electrical side of the install. NFPA 54 (the National Fuel Gas Code) governs the gas line. Gas line work either ties into the existing gas line at the meter or requires a new branch from the meter to the generator location. The gas pressure at the unit has to meet manufacturer specifications.
Propane is the alternative when natural gas is not available. Run time is determined by tank size and the generator’s consumption rate. A 22 kW generator at moderate load consumes roughly 2.5 gallons per hour; a 500-gallon tank stores ~400 gallons usable (tanks fill to ~80% for vapor expansion). That works out to ~160 hours of run time at moderate load before the tank is empty.
Tank sizing matters. A 250-gallon tank for a 22 kW unit only carries ~80 hours of continuous run, fine for a one-day outage, marginal for a multi-day freeze event. We recommend tank sizing for the worst-case outage the homeowner wants the unit to ride out.
Diesel is more common in commercial and large residential installs. Storage is on-site in a fuel tank, usually 50-200 gallons for residential. Diesel has higher fuel-to-runtime efficiency than propane but requires periodic fuel rotation (diesel deteriorates over time) and the tank itself adds cost and footprint.
The transfer switch separates utility power from generator power per NEC 702.5. Three categories cover most residential installs:
For whole-home automatic backup, ATS is the right choice. For partial backup of selected critical loads, manual transfer or interlock can work.
Generator installs are inspected for both the electrical and (in natural-gas installs) the gas-line work. Inspection points typically include:
When an inspection is required, it must be signed off before the unit is commissioned and put into service. Skipping a required inspection means the install is not legal and the homeowner’s insurance may not cover claims that arise.
A whole-home generator is not install-and-forget. Manufacturer maintenance schedules typically include:
The homeowner can perform some of this maintenance; many prefer a service contract that handles it on schedule. Maintenance is not optional, a generator that has not been started in two years is unlikely to start when the power goes out.
Commercial generator installs share the basics of residential installs but operate under different code sections and have different sizing logic:
Commercial scopes are coordinated with the building owner’s mechanical engineer and the AHJ. We work with the consulting engineer on commercial installs to ensure the generator and transfer switch are correctly sized for the actual load profile.
A whole home standby generator is automatic, runs on natural gas or LP, and powers selected (or all) circuits during an outage. An interlock kit lets a portable generator safely back-feed the panel through a breaker. Whole home is more expensive and hands-off; interlock is cheaper and requires you to start the generator manually.
Generator sizing starts with the loads you want to keep on (HVAC, refrigeration, well pump, medical equipment, lighting). We run the load calculation and recommend a size that matches without oversizing.
Outside the home on a concrete pad, away from windows and air intakes per manufacturer and code clearance rules. We confirm the pad location during the site visit.
Yes - both the electrical interconnect and the gas connection (or fuel storage for LP) typically require permits and inspection. We handle the permit application as part of the project.
A typical install runs 2-4 days on site once the equipment arrives, plus permit and inspection scheduling. Larger or more complex projects can extend; we confirm the timeline in the written scope.
Pick the location closest to your property to reach the local team and request a real plan.
