How much does a whole house generator cost?

A standby generator unit costs $3,000-$15,000+ depending on size. Installation adds $3,000-$7,000 (transfer switch, electrical, gas line, pad, permits). Total installed cost: $7,000-$12,000 for a basic 14-16 kW system or $10,000-$16,000 for a popular 20-24 kW whole house system. Larger 30+ kW units cost $15,000-$25,000+ installed. What size generator do I need for my house?

What size generator do I need for my house?

For essential circuits only (lights, fridge, furnace, sump pump): 10-16 kW. For most of the house without central AC: 14-20 kW. For whole house including central AC: 20-30 kW. The most popular residential size is 20-24 kW, which handles most homes with central AC. Add up your appliance wattages and account for starting watts (motors need 2-3x running watts). Is natural gas or propane better for a generator?

Is natural gas or propane better for a generator?

Natural gas is best if you have a gas line — unlimited fuel supply, no storage tank, $2-$5/hour operating cost. Propane is best in areas without natural gas — stored in a tank, higher BTU output, $3-$6/hour. A 500-gallon propane tank runs a 20-24 kW generator for 5-7 days. Dual-fuel models offer maximum flexibility. How long do whole house generators last?

How long do whole house generators last?

Quality standby generators last 15-30 years with proper maintenance. They require annual service ($200-$500) including oil changes, filter replacements, and battery checks. Most generators exercise automatically for 10-15 minutes weekly to stay ready. Natural gas units tend to have slightly longer lifespans than propane units.

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Woodworking & Lumber

Whole House Generator Guide: Types, Sizing, Cost & Installation

Lumberama Editorial Team, Home Power & Electrical Specialists Sep 5, 2026 9 min read

Types of Generators

Portable generators: Gasoline or dual-fuel powered. Manual start and connection. Output: 3,000-12,000 watts. Cost: $300-$3,000. Requires manual setup during outage. Not whole house backup (powers select circuits).

Standby generators (whole house): Permanently installed outside home. Automatic startup within 10-30 seconds of outage. Output: 10,000-50,000+ watts. Natural gas or propane fuel. Cost: $3,000-$15,000+ (unit only). Automatic transfer switch included. True whole house backup.

Inverter generators: Clean power for sensitive electronics. Quieter operation. Lower output (2,000-7,500 watts). Cost: $500-$5,000. Best for supplemental or RV use.

Sizing Your Generator

Calculate your load: List all circuits and appliances you want to power. Add wattage for each item. Account for starting watts (motors need 2-3x running watts).

Common wattage requirements: Central AC (3-5 ton): 3,500-6,000 running / 7,000-12,000 starting. Refrigerator: 150-400 running / 1,200 starting. Furnace blower: 500-700 running / 1,500 starting. Well pump: 750-1,500 running / 2,500 starting. Sump pump: 500-1,000 running / 2,000 starting. Lighting (whole house): 1,000-3,000 running. Electric range: 3,000-5,000 running. Electric water heater: 4,500 running.

Sizing guidelines: Essential circuits only: 10-16 kW. Most of home (no central AC): 14-20 kW. Whole house with central AC: 20-30 kW. Large home with all electric: 30-50 kW.

Most popular residential sizes: 20-24 kW handles most homes with central AC.

Fuel Types

Natural gas: Unlimited fuel supply (utility connection). No fuel storage needed. Slightly lower BTU output than propane. Best choice if natural gas line available. Cost per hour of operation: $2-$5.

Propane (LP): Stored in tank on property (250-1,000 gallon). Must be refilled periodically. Higher BTU output than natural gas. Good for areas without natural gas. 500-gallon tank runs 20-24 kW generator for 5-7 days. Cost per hour: $3-$6. Tank cost: $1,500-$3,500 (500 gallon).

Diesel: Most efficient fuel consumption. Longer engine life. More expensive units. Fuel storage required. Best for commercial or very large residential.

Dual fuel: Runs on natural gas or propane. Maximum flexibility. Cost: 10-20% more than single fuel.

Cost

Generator unit: 10-14 kW: $3,000-$5,000. 16-20 kW: $4,500-$7,500. 22-24 kW: $5,500-$9,000. 30-48 kW: $8,000-$15,000+.

Installation: Automatic transfer switch: $500-$1,500. Electrical work: $1,000-$3,000. Concrete pad: $200-$500. Gas line extension: $500-$2,000. Permits: $200-$500. Total installation labor: $3,000-$7,000.

Total project (unit + install): Basic (14-16 kW): $7,000-$12,000. Mid-range (20-24 kW): $10,000-$16,000. Premium (30+ kW): $15,000-$25,000+.

Ongoing costs: Annual maintenance: $200-$500. Fuel (during outage): $2-$6/hour. Exercise cycle fuel: $10-$30/month.