Whole house generators range from $3,000 to $15,000+ depending on wattage and fuel type, but the real cost includes installation, permits, and ongoing maintenance. Getting an accurate price means understanding what size you need, comparing fuel options, and knowing what to expect from the quote-to-installation process. Here's how to navigate the decision without overpaying.
Understanding Generator Size and Wattage
Your home's power needs determine the generator size you'll buy. Most homes use between 5 kW and 20 kW; a 10 kW unit covers average household loads like HVAC, water heater, and appliances, while larger homes or those with electric heating may need 15–20 kW or more.
Get a professional load calculation during your quote process—don't guess. The installer will review your electrical panel, assess which circuits you want to back up, and recommend an appropriately sized unit. Oversizing wastes money; undersizing leaves you without critical power.
Comparing Fuel Types and Running Costs
Natural gas generators are the most popular choice. They cost $4,000–$10,000 installed and run on your existing gas line, eliminating fuel storage concerns. Monthly operating costs are typically $15–$30 if you run a monthly test cycle.
Propane units ($5,000–$12,000 installed) work well in rural areas without natural gas. You'll need an on-site tank (500–1,000 gallons), and propane prices fluctuate seasonally.
Diesel generators ($6,000–$14,000+) are rugged and fuel-efficient but noisier and require more maintenance. Diesel fuel can degrade in storage, so you'll need fuel stabilizers.
Dual-fuel models offer flexibility but cost more upfront ($7,000–$15,000+). They're worthwhile if you want backup fuel options during extended outages.
What's Included in the Quote
When you request a generator quote, the price should break down into:
- Unit cost: The generator itself (typically $2,000–$8,000 depending on brand and wattage)
- Installation labor: $1,500–$3,500 for site prep, electrical connections, and fuel line installation
- Permits and inspections: $300–$1,000 (varies by municipality; some jurisdictions bundle this with labor)
- Transfer switch: $500–$2,000 (this critical safety component automatically switches your home to generator power)
- Disconnect safety switch: $200–$500 (required by code in many areas)
- Fuel tank or line setup: Free if you use natural gas; $500–$2,000 for propane tank installation
Ask your installer to itemize every line. Vague quotes hide surprises during installation.
Installation Timeline and Logistics
Plan for 2–4 weeks from quote approval to completion, depending on permit wait times. The actual installation takes 1–3 days.
During installation, the installer will:
- Pour a concrete pad or secure the unit to your foundation
- Run fuel lines and electrical conduits
- Install the transfer switch and disconnect switch
- Connect to your electrical panel (requires a licensed electrician in most states)
- Test the unit under load
- Provide you with operation and maintenance manuals
Your electrician must pull permits in your jurisdiction. Some areas require inspections after rough-in (before drywall or final connections) and again after completion. Budget time for these inspections—they typically take 1–2 weeks to schedule.
Maintenance and Warranty Costs
Whole house generators need annual service: filter changes, fluid checks, load testing, and spark plug replacement. Budget $150–$300 per year for professional maintenance.
Most units come with 5–10 year warranties covering parts and labor. Extended warranties ($500–$1,500) can protect you beyond that timeframe. Read the fine print—some warranties only cover factory defects, not wear-and-tear items like filters.
Getting Multiple Quotes
Always compare at least three quotes. Reputable installers will ask detailed questions about your home's power needs, fuel availability, and budget. If a quote is significantly lower than others, ask why—cheaper doesn't mean better workmanship or equipment.
Mercoly helps you compare and find trusted generators and backup power providers in your area, so you can review quotes side by side without wasting time on cold calls.
Frequently Asked Questions
Q: How long can a whole house generator run continuously? Most units are designed to run 24/7 during an outage, but you'll need to refuel propane tanks or monitor fuel levels; natural gas units run indefinitely as long as your gas supply is active.
Q: Do I need a permit to install a whole house generator? Yes—virtually all jurisdictions require electrical and building permits because generators connect to your home's main electrical system and must meet code for safety and grounding.
Q: Will my generator automatically start when the power goes out? Yes, most modern whole house generators have automatic transfer switches that detect an outage and start the engine within seconds, though manual-start models are cheaper ($500–$1,000 less) if you're comfortable starting it by hand.
Get quotes from multiple installers today and compare pricing, timelines, and included services.