generator installation
Pure Home Electric offers generator installation for homeowners throughout the St. Louis metro area. Licensed and insured.*24/7 emergency service available.
protect your biggest asset with a home generator installation in st louis
Standby Generator
Installation
Licensed, permitted, and done right the first time.
St. Louis loses power. Ice storms load up service drops until masts snap. Summer thunderstorms push straight-line winds through tree canopy and into overhead lines. In the 2006 ice storm alone, over 500,000 households and businesses in the metro lost power, some for more than a week. In 2025, a single severe weather event knocked out service to over 136,000 Ameren Missouri customers in one evening. These are not rare events. They are the expected pattern in a metro area that sits at the intersection of every major storm track that crosses the Midwest.
A standby generator restores power to your home within seconds of an outage, automatically, without anyone needing to be home to start it. Pure Home Electric installs residential standby generators throughout the St. Louis metro, including St. Louis City, St. Louis County, and St. Charles County. We handle the full installation: generator placement, concrete pad, automatic transfer switch, electrical panel integration, fuel line connection coordination, permitting, and Ameren coordination.
Call (314) 649-8687 for a free estimate.
helpful info about generators
About
Standby Generators
A standby generator is a permanently installed unit that sits outside your home on a concrete pad, connected to your natural gas line or a propane tank and wired into your electrical panel through an automatic transfer switch (ATS). It monitors the utility power feed continuously. When grid power drops, the ATS detects the loss, signals the generator to start, and transfers your home’s electrical load from the grid to the generator. The entire sequence takes 10 to 30 seconds depending on the unit.
When Ameren restores grid power, the ATS detects the return, transfers the load back to the utility feed, and signals the generator to shut down. No manual intervention at any point. If you are at work, traveling, or asleep when the outage hits, the generator handles it.
Standby generators run a brief self-test cycle weekly (typically 15 to 20 minutes) to keep the engine and battery in ready condition. Beyond that, they sit idle until needed.
Sizing: How Much Generator Do You Need
Generator sizing is not a guess. It is a load calculation based on the specific circuits and equipment in your home that need to run during an outage. Undersizing means the generator overloads and shuts down when too many loads run at once. Oversizing means you paid for capacity you will never use.
The sizing question comes down to a choice between powering select circuits (a managed-load approach) or powering the entire home.
Essential circuits only (10kW to 16kW). This approach powers the loads that matter most during an outage: the refrigerator, freezer, lighting, sump pump, well pump (if applicable), a few outlets, and the HVAC blower or a window unit. It does not power the electric range, the clothes dryer, the electric water heater, or the central AC compressor simultaneously. For homes with natural gas HVAC and a gas water heater, a 10kW to 16kW unit covers the essentials comfortably. This is the most common configuration for budget-conscious installations.
Whole-home coverage (16kW to 22kW). A 16kW to 22kW unit can power most St. Louis homes in their entirety, including central air conditioning. A 22kW generator is the sweet spot for a typical three- to four-bedroom home with a 200A service, one central AC unit, and standard residential appliances. This is the configuration that lets life continue normally during an outage. The AC runs, the kitchen works, the home office stays online, and the sump pump never stops.
Large homes and high-demand installations (22kW to 48kW and above). Homes with multiple HVAC zones, pools, workshops, EV chargers, or all-electric systems may need 30kW or more. At this scale, load management systems can selectively cycle non-critical loads to keep the generator within its rated capacity, reducing the required generator size and cost.
We perform a load calculation during the estimate based on your panel schedule, your installed equipment, and what you want running during an outage. The calculation determines the generator size, not a sales pitch.
Fuel Options: Natural Gas vs. Propane
Standby generators in the St. Louis area run on natural gas or liquid propane (LP). The right choice depends on what is available at your property.
Natural gas. If your home has an existing Ameren Missouri natural gas connection, natural gas is usually the best option. The fuel supply is continuous. There is no tank to refill, no fuel to go stale, and no delivery truck to schedule. The generator runs as long as the gas line has pressure, which means it can sustain power through extended outages lasting days or weeks. Natural gas is also the lowest cost per hour of operation. Most residential standby generators in the metro install on natural gas.
Propane. Propane is the solution for homes without a natural gas connection. It requires a dedicated propane tank (typically 250 to 500 gallons for a whole-home generator) installed at the proper setback distance from the home and any other structures. Run time depends on tank size and generator load. A 500-gallon tank powering a 22kW generator at 50% load provides roughly 4 to 5 days of continuous operation before refueling. Propane does not degrade over time the way gasoline or diesel does, which is an advantage for equipment that sits idle for months between outages.
Natural gas generator installations require coordination with Ameren Missouri’s gas division to verify the existing gas line can supply the required BTU load and, in some cases, to upgrade the gas meter or service line. We coordinate this as part of the installation process.
Maintenance
A standby generator that never gets maintained is a standby generator that fails on the night you need it. These are internal combustion engines with oil, filters, spark plugs, and coolant (on liquid-cooled units). They need the same periodic maintenance as any engine.
Manufacturer-recommended maintenance intervals for most residential standby generators include an oil and filter change every 200 hours of operation or annually (whichever comes first), air filter inspection and replacement, spark plug inspection, battery check, and a full operational test. Most homeowners spend $200 to $400 per year on professional maintenance.
The weekly self-test cycle is not a substitute for annual maintenance. The self-test confirms the engine starts and the ATS functions. It does not check oil condition, filter cleanliness, coolant level, or battery health.
We offer maintenance service for generators we install. Ask about maintenance plans during your estimate.
rules and regulations
Transfer Switches:
ATS vs. Manual
The NEC requires a transfer switch for all generator installations to prevent backfeeding. Backfeeding occurs when generator power feeds back through the panel, through the meter, and onto the utility lines. It can electrocute utility workers repairing downed lines and is a code violation that fails inspection every time.
Automatic transfer switch (ATS). Standard on standby generator installations. Detects outage, starts generator, transfers load, and reverses the process when utility power returns. No one needs to be home. This is what makes a standby generator a standby generator.
Manual transfer switch. Used with portable generators. Requires the homeowner to start the generator, run a cord to the power inlet box, and manually flip the transfer switch to move selected circuits from utility to generator power. Less expensive but entirely manual. If you are not home when the power goes out, the generator does not run. We install manual transfer switches for homeowners who already own or plan to purchase a portable generator, but for permanent standby installations, an ATS is the standard.
Under the 2023 NEC, a whole-house transfer switch installed outside the home can serve as the required exterior emergency disconnect (NEC 230.85) if it is listed as suitable for use as service equipment. This can simplify the installation on homes that would otherwise need a separate emergency disconnect. We evaluate this option on every installation where the 2023 NEC applies.
our generator installation process
What the Generator Installation
Includes
A standby generator installation is not just setting a unit on a pad and plugging it in. It is an electrical, mechanical, and permitting project with multiple coordination points.
Site assessment and load calculation. We evaluate your panel, your electrical service, your fuel source, and the physical location for the generator. Placement must meet manufacturer clearance requirements, NEC setback distances, local zoning setbacks, and Ameren specifications (the generator must be at least 6 feet from the electric meter and 3 feet from the gas meter). We also evaluate the concrete pad location for drainage, accessibility for maintenance, and noise impact on adjacent living spaces and neighboring properties.
Concrete pad. The generator sits on a level concrete pad or a prefabricated composite pad rated for the unit’s weight. The pad must be sized to the generator footprint and level within the manufacturer’s tolerance.
Automatic transfer switch (ATS). The ATS is the bridge between the utility feed, your panel, and the generator. It is required by the NEC (Article 702.5) for all generator installations. The ATS must be rated for the connected load and installed per the manufacturer’s specifications. On whole-home installations with a 200A service, the ATS is typically a 200A unit installed between the meter base and the main panel. On managed-load installations, a smaller ATS or a load-center-style switch may serve selected circuits only.
Electrical connections. We run properly sized conductors from the generator to the ATS and from the ATS to the panel. Wire gauge is determined by the generator’s output capacity, the distance of the run, and the ATS configuration. All connections are made in compliance with the current NEC edition adopted by your municipality.
Fuel line connection. For natural gas installations, a dedicated gas line is run from the existing gas supply to the generator. This work may require a licensed plumber depending on your municipality’s requirements. We coordinate with the plumber and with Ameren Missouri’s gas division to ensure the gas service is adequate for the combined household and generator load. For propane installations, we coordinate with the propane supplier for tank placement and line installation.
Permitting and inspection. Generator installations in the St. Louis metro typically require both an electrical permit and a mechanical or fuel permit. Some municipalities require a separate building permit for the concrete pad if it exceeds a certain size. We handle the permit applications and schedule the inspections. The installation is not complete until it passes inspection.
Ameren coordination. On whole-home installations where the ATS is installed between the meter and the main panel, Ameren may need to pull the meter during installation. We coordinate the disconnect and reconnect. For natural gas installations, we verify the gas meter sizing with Ameren’s gas division before the installation date.
Startup and commissioning. After passing inspection, we power up the generator, run it through its startup sequence, simulate a utility outage to verify automatic transfer, and confirm that all intended circuits receive power. We walk you through the weekly self-test cycle, the maintenance schedule, and the manual override procedure.
FAQs
Frequently Asked
Questions
What Does Generator Installation Cost?
Total installed cost for a residential standby generator in the St. Louis area typically falls between $6,000 and $15,000. That range covers the generator unit, the automatic transfer switch, the concrete pad, electrical connections, fuel line work, permitting, and labor.
Where a specific installation lands within that range depends primarily on the generator size. A 10kW essential-circuits unit is at the lower end. A 22kW whole-home unit with a 200A ATS is in the $10,000 to $15,000 range. Units above 22kW, installations requiring gas line upgrades, homes needing a panel upgrade to accommodate the ATS, and propane installations with tank costs push toward the higher end or above.
The generator unit itself accounts for roughly half to two-thirds of the total cost. A 22kW natural gas unit runs approximately $5,000 to $6,000 for the equipment. Installation labor, the ATS, the pad, fuel line work, and permits account for the balance.
We provide a fixed, all-inclusive price before any work begins. The estimate includes every component listed above. No separate invoices from subcontractors, no permit surcharges, no surprise fuel line costs.
How long does a generator installation take?
Most residential standby generator installations take one to two days of on-site work once permits are approved and the equipment is on hand. The concrete pad may need to cure before the generator is placed, which can add a day. The overall timeline from signed contract to operational generator is typically two to four weeks, depending on permit turnaround in your municipality and equipment availability.
Will a generator power my entire house?
It depends on the generator size and your home’s electrical load. A 22kW unit powers most three- to four-bedroom homes in their entirety, including central air conditioning. Smaller units (10kW to 16kW) power essential circuits only. We perform a load calculation during the estimate to match the generator size to your specific requirements and budget.
Can I install a generator if I don't have natural gas?
Yes. Propane-fueled standby generators work anywhere a propane tank can be placed. The tank is installed at a code-required setback distance from the home and any other structures. We coordinate with a propane supplier for tank placement and service. Propane units are functionally identical to natural gas units in how they operate and integrate with your electrical system.
How loud is a standby generator?
Most modern residential standby generators operate between 60 and 70 decibels at the manufacturer’s rated measurement distance, which is comparable to a normal conversation or a central air conditioner condenser. Air-cooled units (common at 22kW and below) tend to run slightly louder than liquid-cooled units (24kW and above). Generator placement matters: positioning the unit away from bedroom windows and neighboring property lines reduces perceived noise. Local zoning may also specify noise limits or minimum setback distances.