Standby Generator Installation Cost Calculator

In 2026, standby generator installation typically costs $8,000 to $18,000 for a complete system, with most homeowners paying around $10,000 to $15,000 for a whole-home unit including the generator, the automatic transfer switch, and the electrical and fuel connections. On a per-kilowatt basis, standby generator systems run about $750 to $900 per kW installed. A smaller essential-circuits system (10-14 kW) can be $6,000-$10,000, while a large whole-home unit (22-26 kW) with a service upgrade, a propane tank, and a long fuel/electrical run can exceed $20,000-$25,000. The cost depends mainly on the generator's capacity in kilowatts (the biggest driver — a whole-home unit is typically 18-26 kW, while essential-circuit coverage needs 10-14 kW), the fuel type (natural gas connected to your utility line is the most convenient, liquid propane from a tank suits homes without gas, and diesel is for larger loads), the transfer switch (a whole-home automatic transfer switch, a load-managed switch, or an essential-circuits switch), the electrical work (a simple panel tie-in, a moderate subpanel/rewire, or a complex service upgrade), and the distance from the electrical panel and fuel source to the generator pad. A standby (whole-home) generator is a permanently-installed backup generator that sits outside the home (like an AC unit) and automatically powers the home during a utility outage — it's hardwired to the electrical panel through an automatic transfer switch (ATS) that detects the outage, disconnects from the grid, and switches to generator power within seconds (then switches back when utility power returns). It runs on natural gas, propane, or diesel (no refueling for gas/propane connected to a supply). Installation involves placing and mounting the generator (on a pad), connecting the fuel (gas line or propane tank), installing the transfer switch, wiring it to the electrical panel, and commissioning/testing the system. Add-ons like a concrete mounting pad, a propane tank and line, a gas line extension, permits and inspection, WiFi monitoring, and a maintenance plan add to the total. Pricing varies by region, the unit size/brand, the fuel, the electrical complexity, and the installer. A smaller essential-circuit system is at the lower end, while a large whole-home unit with electrical and fuel work is at the higher end. This calculator lets you set the capacity, fuel, transfer switch, and electrical work to estimate your project. A standby generator provides automatic, reliable backup power and adds home value.

The size of standby generator you need depends on how much of your home you want to power during an outage — a whole-home generator (powering everything) typically needs 18 to 26 kW for an average home, while an essential-circuits or 'managed' approach (powering just the critical items) can work with a smaller 10 to 14 kW unit. A professional performs a load calculation to size it correctly for your specific home. Here's how sizing works. Two approaches to sizing: Whole-home coverage — to power the entire home (everything, including large loads like central AC, electric range, electric water heater, well pump) during an outage, you need a larger generator (typically 18-26 kW for an average home; larger homes with multiple AC units or heavy electric loads may need 26-48 kW). This powers everything automatically — the most convenient (you don't notice the outage). The most popular for full backup. Essential/managed coverage — to power just the essential circuits (refrigerator, furnace/heat, some lights, outlets, sump pump, well) — not everything at once — a smaller generator (10-14 kW) can suffice, often with load management (the system sheds/prioritizes loads so the smaller generator handles the essentials). More economical, but you may not run everything simultaneously (e.g., not the AC and the range at once). A good budget option. How a pro sizes it (load calculation): Identify the loads — list the appliances/systems you want to power (and their wattage), especially the large ones (central AC — the biggest, often 3-5+ tons; electric heat/furnace blower; well pump; electric range/oven; electric water heater; etc.). Starting loads — account for motor-starting surges (AC compressors, well pumps, motors draw extra wattage on startup). The generator must handle the surge. Sum and size — total the running and starting loads to determine the required kW, then size the generator (with some headroom). A pro does this calculation. Load management — if you want a smaller (cheaper) generator, load management (smart switches that prioritize/shed loads) lets a smaller unit cover the essentials (managing peak demand). Common sizes: Essential circuits (managed) — ~10-14 kW. Whole-home (average home) — ~18-26 kW (a 22 kW unit is a very common whole-home size). Large home / heavy loads — ~26-48 kW. Small/critical only — some use smaller (but for a whole-home standby, 18+ is typical). Factors that affect the size: Home size — larger homes (more square footage, more loads) need more. AC — central air conditioning is a major factor (it's a big load); the number/size of AC units matters a lot. Heating — electric heat (vs gas) adds significant load. Electric appliances — an electric range, water heater, dryer, and EV charger add load (vs gas versions). Well pump — adds a starting load. Future needs — sizing for additions or an EV charger. Don't undersize (or oversize): an undersized generator can't handle the load (it overloads, or can't start the AC). An oversized one costs more than needed (and runs inefficiently). Right-sizing (via a load calculation) is key — which is why a professional assessment matters. Recommendation: have a professional perform a load calculation based on your home's specific loads (especially the AC and any electric heat/appliances) and your coverage goal (whole-home vs essentials). They'll recommend the right kW. Don't guess — proper sizing ensures reliable backup. Considerations: a whole-home standby generator typically needs 18-26 kW (more for large homes/heavy electric loads), while an essential-circuits/managed approach can use 10-14 kW. A pro performs a load calculation (factoring the AC, heat, and appliances) to size it. This calculator lets you enter the kW. So the standby generator size you need depends on your coverage goal — 18-26 kW for whole-home backup (more for large or heavy-electric homes), or 10-14 kW for essential circuits with load management. A professional load calculation (accounting for your AC, heating, and appliances) determines the right size. Get a pro assessment to size it correctly — proper sizing ensures reliable whole-home or essential backup power.

The best fuel for a standby generator depends on what's available at your home and your priorities — but for most homes, natural gas is the best and most popular choice if you have a utility gas line (unlimited fuel, no refueling, convenient), while propane is the best option for homes without natural gas (clean, stores well), and diesel is best for very large loads or commercial use. Here's the comparison. Natural gas: Best for — homes with a natural gas utility connection (the most common and convenient choice for them). How it works — the generator connects to your home's natural gas line (the utility supply) — providing a continuous, unlimited fuel supply. Pros — Unlimited fuel — connected to the utility, it runs indefinitely (no refueling, no running out during a long outage). The biggest advantage. Convenient — no fuel storage, no refilling, always ready. Clean-burning — burns cleaner than diesel. Lower fuel cost — natural gas is typically economical. No tank — no fuel tank to install/maintain. Cons — requires a natural gas line (not available everywhere/rural); depends on the gas utility (which usually stays on during outages, but not always — e.g., some disasters); slightly lower power density than propane/diesel (may need a slightly larger unit). The go-to for gas-connected homes. Propane (LP): Best for — homes without natural gas (rural, or no gas line) — the most common alternative. How it works — the generator runs on liquid propane from an on-site tank (which you fill/refill). Pros — No gas line needed — works anywhere (you supply a tank). Clean-burning — burns clean, like natural gas. Stores indefinitely — propane doesn't degrade in storage (unlike diesel/gasoline) — good for standby use. High energy content — slightly more power-dense than natural gas. Widely available — propane delivery is common. Cons — finite supply — limited by the tank size (a large tank lasts a long time, but can run out in a very long outage — refill needed); requires a propane tank (install/rent/buy) and refills; fuel cost varies. The best choice for homes without natural gas. Diesel: Best for — very large loads, commercial/industrial use, or where preferred (less common for typical homes). Pros — power-dense and efficient, durable engines (good for large/long runs), and diesel is energy-dense. Cons — requires a fuel tank and refueling (and diesel degrades over time — needs fuel maintenance/treatment for standby use); louder; emissions; less clean than gas/propane; more maintenance. Used more for large/commercial standby. Less common for homes. How to choose: Have natural gas — use natural gas (unlimited, convenient, no refueling). The top choice for gas-connected homes. No natural gas — use propane (a tank) — the best option for homes without gas. Very large/commercial — diesel may suit (or large gas/propane). Convenience priority — natural gas (no refueling) wins; propane is close (with a large tank). The most popular: for residential standby generators, natural gas (if available) is the most popular and recommended (unlimited fuel, no refueling), followed by propane (for homes without gas). Diesel is mainly for large/commercial. Considerations: natural gas is the best standby generator fuel if you have a utility gas line (unlimited, convenient, clean), propane is best for homes without natural gas (clean, stores well, needs a tank), and diesel suits very large/commercial loads. Choose based on what's available at your home. This calculator includes all three fuels. So for most homes, natural gas is the best standby generator fuel if you have a gas line (unlimited fuel, no refueling, convenient and clean), while propane is the best choice for homes without natural gas (clean and stores indefinitely, but needs a tank), and diesel is mainly for large or commercial loads. Pick the fuel based on what's available — natural gas if you have it, otherwise propane. Both keep your home powered reliably.

An automatic transfer switch (ATS) is the device that safely and automatically switches your home's electrical supply between the utility grid and the standby generator — and you need one because it's what makes a standby generator 'automatic' (detecting an outage and starting/connecting the generator within seconds, then switching back when power returns) and, critically, it prevents dangerous backfeed that could harm utility workers or damage equipment. It's an essential, required part of a standby generator system. What an automatic transfer switch does: Monitors the utility power — the ATS constantly monitors the incoming utility power. Detects an outage — when it detects a utility outage (power loss), it signals the generator to start. Transfers to generator power — once the generator is running and ready (a few seconds), the ATS disconnects the home from the utility grid and connects it to the generator — restoring power automatically (typically within ~10-30 seconds of the outage). Transfers back — when utility power returns (and is stable), the ATS switches the home back to the grid and signals the generator to shut down (after a cooldown). All automatic. No manual action — all of this happens automatically, without you doing anything (unlike a portable generator, which you manually start and connect). You don't even need to be home. Why you need one (it's essential): Makes it automatic — the ATS is what makes a standby generator 'standby/automatic' — it provides seamless, automatic backup (the whole point of a standby system) without manual intervention. Without it, the generator couldn't auto-start/transfer. Safety — prevents backfeed (CRITICAL) — the ATS isolates the home from the utility grid when on generator power. This prevents 'backfeed' — generator power feeding back into the utility lines — which could electrocute utility workers repairing the lines (a deadly hazard) and damage equipment. The transfer switch's isolation is a critical safety function (and required by code). Never connect a generator without proper transfer equipment. Protects the generator/home — it ensures the generator and grid are never connected simultaneously (which would damage the generator/electronics when utility power returns). The ATS manages the transition safely. Code requirement — a transfer switch (ATS or a manual transfer switch) is required by electrical code for connecting a generator to a home's wiring. It's not optional. Types: Whole-home ATS — transfers the entire electrical panel (the whole home) to generator power — for whole-home coverage. Essential-circuits / load-managed switch — transfers only select essential circuits (or uses load management to prioritize loads) — for partial coverage with a smaller generator. Manual transfer switch — (for portable generators) requires manually switching — but standby systems use an automatic one. The role in the system: the ATS is the 'brain' that connects the generator to the home safely and automatically. It's installed near the electrical panel and wired between the utility, the panel, and the generator. A pro installs and configures it. The bottom line: the automatic transfer switch is an essential, code-required component that makes the standby generator automatic (auto-detect, auto-start, auto-transfer) and, critically, ensures safety (preventing dangerous backfeed) and protects the equipment. You can't have a proper automatic standby generator without one. Considerations: an automatic transfer switch (ATS) automatically switches your home between utility and generator power (detecting outages and transferring within seconds, both ways) — and it's essential because it makes the generator automatic and, critically, prevents dangerous backfeed (protecting utility workers) and is code-required. This calculator includes transfer switch options. So an automatic transfer switch is the essential device that automatically switches your home's power between the grid and the standby generator (detecting outages and transferring within seconds) — and you need one because it makes the generator automatic and, critically, prevents dangerous backfeed that could electrocute utility workers. It's a required, safety-critical part of any standby generator system. A professional installs it as part of the system.

Yes — standby generator installation almost always requires permits (electrical, and often gas/fuel and building permits) and should absolutely be done by professionals (a licensed electrician, and often a gas fitter/plumber for the fuel) — given the high-voltage electrical work, the fuel (gas/propane) connections, the transfer switch and backfeed-prevention requirements, and the code/inspection requirements. This is not a DIY project. Permits required: Electrical permit — connecting a generator and transfer switch to the home's electrical panel requires an electrical permit and inspection (it's significant electrical work — high voltage, the panel, the transfer switch). Required by code. Gas/fuel permit — connecting the generator to a natural gas line, or installing a propane tank and line, typically requires a gas/plumbing permit and inspection (for safe fuel connections). Often required. Building/mechanical permit — placing the generator (the pad, location, clearances) may require a building or mechanical permit (and must meet placement codes — distance from the house, windows, property lines, etc.). Local requirements — permit requirements vary by locality (and sometimes HOA rules) — the installer handles the permits. Why permits — they ensure the installation meets electrical, gas, and safety codes (for your safety and proper, legal, insurable operation). Skipping them risks safety, code violations, and insurance/resale issues. Why professional installation is essential: High-voltage electrical work — connecting to the electrical panel, installing the transfer switch, and wiring the generator is serious high-voltage work — dangerous if done improperly (shock, fire). A licensed electrician is needed (and required). Transfer switch / backfeed — the automatic transfer switch must be properly installed to safely isolate the home from the grid (preventing dangerous backfeed that could kill utility workers). This is safety-critical and code-required — a pro ensures it's done right. Fuel connections — connecting natural gas (or installing a propane tank/line) requires a qualified gas fitter/plumber — gas leaks are dangerous (fire/explosion, CO). Proper, leak-free, code-compliant connections are essential. Proper sizing/setup — a pro sizes the generator (load calculation), selects the right transfer switch, and configures/commissions the system (testing it works). Placement/codes — the generator must be placed correctly (clearances from the house, windows, combustibles, property lines — for safety and code, and exhaust/CO considerations). A pro ensures compliant placement. Code compliance/inspection — the installation must meet electrical and gas codes and pass inspections — a pro ensures this (and pulls the permits). Manufacturer warranty — professional installation is typically required for the generator's warranty to be valid (and often for the extended warranty). Commissioning — the system must be commissioned (started, configured, tested) — often by an authorized dealer/technician (sometimes required for warranty). Why not DIY — the high-voltage electrical, the gas/fuel connections, the safety-critical transfer switch/backfeed prevention, the code/permit/inspection requirements, and the warranty all make this a professional job. DIY is unsafe, likely illegal (without permits/licensing), and would void the warranty. The right approach: hire a qualified installer — typically a licensed electrician (often an authorized generator dealer/installer) who handles the electrical, transfer switch, and commissioning, and a gas fitter/plumber for the fuel (or a company that does both). They pull the permits, install to code, and commission the system. Many generator brands have authorized installer networks. Considerations: standby generator installation requires permits (electrical, gas/fuel, often building) and must be done by professionals (a licensed electrician and a gas fitter) — given the high-voltage work, fuel connections, safety-critical transfer switch, code/inspection requirements, and warranty. It is not DIY. This calculator includes a permit add-on and estimates professional installation. So yes, standby generator installation requires permits (electrical, gas/fuel, and often building) and must be done by professionals — a licensed electrician for the high-voltage and transfer-switch work, and a gas fitter/plumber for the fuel connections. The safety-critical electrical and fuel work, code requirements, and warranty make professional installation essential. Hire a qualified, authorized installer who handles the permits, code-compliant installation, and commissioning. Never DIY a standby generator.

Standby generator installation typically takes 1 to 3 days of on-site work, though the overall project timeline (from order to a running system) is often 4 to 8 weeks when you factor in unit lead times, permits, and any fuel/electrical preparation. The hands-on installation itself is usually completed in a day or two for a standard job. The on-site installation: Standard installation — for a typical whole-home standby generator with natural gas (existing line nearby) and a straightforward electrical tie-in, the physical installation is usually 1-2 days: placing/mounting the generator (on the pad), connecting the fuel line, installing the transfer switch, wiring it to the panel, and commissioning/testing. Often done in a day or two. More complex — installations needing more work take longer (2-3+ days): a propane tank installation, a long fuel line or electrical run (trenching), an electrical service upgrade, a complex panel/subpanel setup, or difficult access/placement. With site prep — if a concrete pad needs to be poured (and cured), or significant trenching/excavation is required, that adds time (pad curing, digging). The overall project timeline (order to running): Unit lead time — the generator unit may need to be ordered (lead times vary — from in-stock to several weeks, depending on the size/brand/availability). This is often the longest part. Permits — pulling the electrical, gas, and building permits takes time (days to weeks, depending on the locality). Required before/around installation. Scheduling — scheduling the installer (and any utility/gas coordination) — popular installers may have a lead time. Fuel coordination — coordinating the gas line (utility) or propane tank delivery/install. Inspection — after installation, inspections (electrical, gas) are scheduled (and the system commissioned). So while the hands-on installation is 1-3 days, the full project (order, permits, prep, install, inspection) often spans 4-8 weeks (sometimes more if the unit has a long lead time or permitting is slow). Planning ahead is wise (especially before storm season). The phases: Site assessment/sizing — a pro assesses and sizes the generator (and quotes). Order — order the unit (lead time). Permits — pull permits. Site prep — pad, trenching, fuel line (as needed). Installation — place the generator, connect fuel, install the transfer switch, wire to the panel (1-3 days). Commissioning/inspection — start, configure, test, and inspect the system. Factors: the unit lead time, permit timelines, the fuel type (a propane tank adds time), the electrical complexity (a service upgrade adds time), site prep (pad, trenching), and installer scheduling. So while the actual standby generator installation is typically a 1-3 day job on-site, plan for a 4-8 week overall timeline (order to running) accounting for unit lead times, permits, and prep. This calculator estimates the cost; plan the timeline with your installer. The hands-on install is quick (1-3 days), but order early — the full project often takes several weeks. Plan ahead, especially before storm season.