A power outage lasting more than a few hours can mean spoiled food, failed sump pumps, and no heat in winter. Getting a backup generator sized and installed correctly is the difference between real protection and an expensive paperweight. Here's what you need to know before spending a dollar.
How Much Does Backup Generator Installation Cost?
Backup generator installation cost varies widely depending on generator type, fuel source, and home size. Here's a realistic breakdown:
- Portable generator (3,000–8,000W): $500–$2,000 for the unit, plus $300–$800 for a transfer switch installation
- Standby generator (8–20 kW, natural gas): $3,000–$6,000 for the unit, plus $1,500–$5,000 for installation
- Whole-home standby generator (20–22 kW): $5,000–$10,000 for the unit, plus $2,000–$6,000 installed
- Large whole-home or small commercial (25–45 kW): $10,000–$25,000+ fully installed
The biggest cost variables are trenching for gas lines, upgrading your electrical panel, permit fees, and whether you need a concrete pad poured for the unit.
Step 1: Calculate How Much Power You Actually Need
Don't guess. Pull out your appliances and add up wattage. Common loads include:
- Refrigerator: 150–200W running, 1,200W startup surge
- Central AC (3-ton unit): 3,500W running, 5,000–7,000W startup
- Electric water heater: 4,000–5,000W
- Sump pump: 800–1,000W running, 1,500–2,000W startup
- Lights and electronics: 500–2,000W depending on home
For most 2,000–2,500 sq ft homes running critical circuits only (HVAC, fridge, sump pump, some lighting), a 14–20 kW standby generator is the sweet spot. If you want whole-home coverage including electric dryers or EV chargers, plan for 22–30 kW minimum.
The startup (surge) wattage of motors is what kills undersized generators. Always size based on the largest motor's surge load, not just running watts.
Step 2: Choose Your Fuel Type
Natural gas is the most popular choice for standby units — no refueling, no storage, and utilities rarely go down during power outages. The downside is it requires a gas line run, which adds cost.
Propane works well in rural areas without natural gas. You'll need a 250–500 gallon tank on-site. Expect $800–$2,500 to install the tank, plus fuel costs.
Diesel makes sense for commercial or agricultural properties needing high output. It's less common in residential settings due to storage regulations and maintenance requirements.
Dual-fuel portable generators (running on gasoline or propane) offer flexibility for occasional use but aren't practical as permanent standby solutions.
Step 3: Understand the Transfer Switch Requirement
This is non-negotiable — never connect a generator directly to your home's wiring. It creates backfeed, which can electrocute utility workers.
You have two main options:
- Manual transfer switch: Less expensive ($300–$600 installed), but requires you to manually switch over during an outage
- Automatic transfer switch (ATS): Detects outages and starts the generator within 10–30 seconds automatically — standard with all standby generators, adds $500–$1,500 to portable generator setups
Whole-house automatic standby generators come with ATS included. It's installed between your utility meter and main panel.
Step 4: Plan for Permits and Inspections
Most jurisdictions require permits for standby generator installation. Expect:
- Electrical permit: Required in virtually every municipality
- Gas line permit: Required when running new gas service
- Building permit: Sometimes required for the concrete pad
Permit fees typically run $50–$300 depending on location. Skipping permits can void your homeowner's insurance coverage and complicate home sales later. Always use a licensed electrician and, where required, a licensed plumber or gas fitter for fuel line work.
Step 5: Hire the Right Installer
Generator installation isn't a DIY project for most homeowners. You need:
- A licensed electrician to handle the transfer switch and panel connection
- A gas fitter or plumber if new fuel lines are required
- Ideally a generator-certified installer familiar with your specific brand (Generac, Kohler, Briggs & Stratton, Cummins, etc.)
Get at least three quotes. Ask each contractor what's included — pad installation, permit pulling, fuel line work, and a load test after installation should all be part of the scope.
Mercoly makes it straightforward to compare and find trusted Generators & Backup Power providers in one place, so you're not cold-calling contractors or guessing at credentials.
What to Watch Out For
- Low-ball quotes that exclude permits, gas line work, or the transfer switch
- Undersized units sold just to close a deal quickly
- No load test performed after installation — always insist on one
- Incorrect placement — generators must be a minimum of 5 feet from windows, doors, and vents per most codes
Use Mercoly to find a qualified generator installer near you and get your backup power sorted before the next outage hits.