How Long Does It Take to Install a Whole-House Generator?
Quick Answer
1–3 days for the physical installation, but the full process including permits, gas line work, and inspections typically spans 2–6 weeks from purchase to first use.
Typical Duration
Quick Answer
The physical installation of a whole-house generator takes 1–3 days, but the complete process from purchase to operational status typically requires 2–6 weeks when factoring in permits, utility coordination, and inspections. Most of the elapsed time is spent waiting for permits and scheduling, not on hands-on work.
Full Project Timeline
| Phase | Duration | Notes |
|---|---|---|
| Site assessment and sizing | 1–2 hours | Electrician evaluates load requirements |
| Equipment ordering | 1–4 weeks | Popular models may have lead times |
| Permit applications | 1–3 weeks | Electrical, building, and gas permits |
| Concrete pad preparation | 1 day | Must cure 24–48 hours before placement |
| Generator placement | 2–4 hours | Crane or equipment for units over 250 lbs |
| Electrical wiring and transfer switch | 4–8 hours | Automatic transfer switch installation |
| Gas line connection | 2–4 hours | Licensed plumber or gas fitter required |
| Testing and commissioning | 1–2 hours | Load testing and programming |
| Final inspection | 1–2 weeks wait | Municipality scheduling dependent |
Installation Time by Generator Size
| Generator Size | Home Size | Installation Time | Typical Cost |
|---|---|---|---|
| 10–14 kW | Small (up to 1,500 sq ft) | 1 day | $3,500–$6,000 |
| 16–20 kW | Medium (1,500–2,500 sq ft) | 1–2 days | $5,000–$9,000 |
| 22–26 kW | Large (2,500–4,000 sq ft) | 2–3 days | $7,000–$12,000 |
| 30–48 kW | Estate/commercial | 2–3 days | $12,000–$20,000+ |
Key Factors Affecting Installation Time
Permit requirements vary dramatically by municipality. Some areas issue electrical permits within days, while others require 2–3 weeks for review. Natural gas connections may need a separate permit from the gas utility, adding another layer of scheduling.
Fuel source impacts complexity. Natural gas installations are generally faster because the gas supply line already exists at the home. Propane installations require tank placement (above or below ground) and dedicated supply lines, adding 4–8 hours of work.
Transfer switch type matters. An automatic transfer switch (ATS) senses power loss and starts the generator within 10–30 seconds. Installing a 200-amp ATS at the main panel takes 4–6 hours. Homes with subpanels or complex electrical systems may require a full day for electrical work alone.
Distance from the main panel and gas meter affects wiring and piping runs. Generators placed more than 25 feet from the electrical panel or gas meter require longer trenching and conduit runs, adding 2–4 hours.
Local code requirements may mandate specific setback distances from windows, property lines, and HVAC equipment. In some cases, the only compliant location requires longer utility runs or additional concrete work.
Permits Typically Required
| Permit Type | Processing Time | Required By |
|---|---|---|
| Electrical permit | 3–10 business days | Municipality |
| Building permit | 5–15 business days | Municipality |
| Gas permit | 3–10 business days | Gas utility or municipality |
| Plumbing permit (propane) | 5–10 business days | Municipality |
| HOA approval (if applicable) | 2–4 weeks | Homeowners association |
What to Expect on Installation Day
Day one typically covers concrete pad pouring (if not done in advance), generator placement, and electrical rough-in. Day two focuses on the transfer switch, gas line connection, and testing. A third day is only needed for large systems, complex electrical configurations, or when propane tank installation runs concurrently.
Most installers recommend scheduling the installation during dry weather, as concrete pads need 24–48 hours to cure and electrical work should not be performed in rain.