Diesel Generator for Sale
Quick Sizing Estimator
Enter your estimated total power requirements to get a sizing recommendation. For critical applications, consult with a professional electrician.
💰 Typical Price Ranges (2024)
Portable (5-15 kW)
Wheeled, gas start
$3K - $10K
Home Standby (15-30 kW)
Automatic transfer switch
$8K - $20K
Commercial (30-150 kW)
Three-phase capability
$15K - $80K
Industrial (150-500 kW)
Heavy-duty continuous
$80K - $300K
* Prices are for generator only. Add $3K-$40K for professional installation depending on complexity.
🏆 Top Diesel Generator Brands
Premium Tier
- • Cummins - Industry leader, 30K-50K hour life
- • Caterpillar - Industrial powerhouse
- • Kohler - Quiet residential specialists
- • Generac - Home standby market leader
Value Tier
- • Perkins - Solid reliability, lower cost
- • John Deere - Agricultural heritage
- • Kubota - Compact and reliable
- • Yanmar - Budget-friendly option
🔧 Maintenance Requirements
• Monthly: Exercise run (30 min at 50%+ load)
• Every 100 hours / Annually: Oil & filter change, fuel filter, air filter, battery check, load test
• Every 400 hours / 2 years: Coolant replacement, fuel system service
• Every 1,000 hours / 3-5 years: Valve adjustment, injector service, battery replacement
Professional maintenance contracts available: $400-$1,200/year depending on size
📋 New vs Used Decision Guide
Choose NEW if:
- ✓ Critical backup application (hospitals, data centers)
- ✓ Long-term ownership (20+ years)
- ✓ Latest emissions compliance required
- ✓ Manufacturer warranty important
- ✓ Financing needed (better rates)
Choose USED if:
- ✓ Budget-constrained (save 40-70%)
- ✓ Temporary/short-term need
- ✓ Non-critical backup application
- ✓ Immediate availability essential
- ✓ Experienced in generator maintenance
🛒 Where to Find Diesel Generators
• Authorized Dealers: Cummins, CAT, Kohler, Generac dealer networks (new + service)
• Industrial Equipment Distributors: Nationwide suppliers with multiple brands
• Online Marketplaces: MachineryTrader, EquipmentTrader (used equipment)
• Auction Sites: Ritchie Bros, IronPlanet (heavy equipment auctions)
• Rental Companies: United Rentals, Sunbelt (used rental fleet sales)
⚠️ Always get pre-purchase inspection for used units ($300-$800 well spent!)
About This Calculator
Compare diesel generator options by power output, fuel consumption, runtime, and total cost of ownership. Find the right generator size for residential, commercial, or industrial backup power needs.
Frequently Asked Questions
What size diesel generator do I need for my home or business?
Generator sizing depends on total wattage of equipment you need to run simultaneously. Residential: Small home (essential circuits — fridge, lights, sump pump): 5-8 kW. Average home (HVAC, kitchen, lights): 10-20 kW. Large home with central AC: 20-30 kW. Commercial: Small office/retail: 20-50 kW. Restaurant: 50-100 kW. Small manufacturing: 100-500 kW. Data center/hospital: 500-2,000+ kW. Sizing formula: List all equipment wattage, add 25% buffer for starting surge (motors require 2-3x running watts to start). Example: Central AC (5,000W running, 15,000W starting) + fridge (700W) + lights (1,000W) + sump pump (1,500W) = peak 18,200W. Select 20 kW generator. Always size for peak/starting load, not just running load — undersized generators cause voltage drops that damage sensitive electronics.
How much does a diesel generator cost to buy and operate?
Purchase price by size (2025, new units): 5-10 kW portable: $2,000-5,000. 10-20 kW standby: $5,000-12,000. 20-50 kW commercial: $10,000-25,000. 50-150 kW industrial: $20,000-60,000. 150-500 kW prime power: $40,000-150,000. 500+ kW: $100,000-400,000+. Installation adds $3,000-10,000 for standby units (concrete pad, transfer switch, fuel tank, electrical connection). Operating costs: Fuel consumption averages 0.06-0.07 gallons per kWh. A 20 kW generator at 75% load burns 1.0-1.2 gallons/hour. At $4/gallon diesel, that is $4-5/hour or $100-120/day for continuous operation. Annual maintenance: oil changes ($100-300 every 250-500 hours), filter replacements, coolant service — budget $500-1,500/year for residential, $2,000-5,000 for commercial units. Diesel generators cost 15-25% more upfront than gas generators but consume 30-40% less fuel per kWh.
What are the advantages of diesel generators over gas or propane?
Diesel generator advantages: (1) Fuel efficiency — diesel engines are 30-40% more fuel efficient than gasoline engines at equivalent power output. A diesel generator produces more kWh per gallon, reducing long-term operating costs. (2) Durability — diesel engines operate at lower RPM (1800 vs 3600 for gas), have no spark plugs or carburetors, and last 20,000-30,000 hours vs 5,000-10,000 for gas. (3) Fuel stability — diesel fuel stores safely for 6-12 months (with stabilizer), while gasoline degrades in 3-6 months. (4) Safety — diesel is less flammable than gasoline (higher flash point: 126°F vs -45°F). (5) Availability during emergencies — diesel is prioritized for emergency vehicles and generators during disasters. Disadvantages: higher upfront cost (15-25% more than gas), louder operation (85-100 dB vs 65-80 dB for gas), cold-start challenges below 0°F (requires block heater), and stricter emissions regulations (EPA Tier 4 compliance adds cost). Best for: extended runtime needs, commercial/industrial use, and backup power systems requiring high reliability.
How do I maintain a diesel generator for maximum lifespan?
Diesel generators last 20,000-30,000 hours (15-25 years of standby use) with proper maintenance. Essential maintenance schedule: Every 250-500 hours (or annually for standby): Change engine oil and oil filter. Replace fuel filter. Check/replace air filter. Inspect belts and hoses. Test battery voltage and connections (starting batteries fail more than engines). Every 1,000-1,500 hours: Replace coolant and thermostat. Clean/test fuel injectors. Inspect alternator brushes and bearings. Load-bank test at 75%+ capacity for 2 hours. Every 5,000 hours: Major overhaul inspection (valve adjustment, cylinder compression test, turbocharger inspection). Critical practices: (1) Run the generator under load for 30 minutes monthly — prevents wet stacking (carbon buildup from unburned fuel). (2) Keep fuel tank full to prevent moisture condensation. (3) Use fuel biocide additive to prevent algae growth in stored diesel. (4) Test the automatic transfer switch quarterly. Biggest maintenance mistake: letting generators sit idle for months then expecting them to start during an emergency.
Should I buy a new or used diesel generator?
Used generators can save 40-60% over new but require careful evaluation. Buy new when: critical application (hospital, data center), warranty is important (typically 2-5 years), emissions compliance required (EPA Tier 4 regulations), and budget allows. Buy used when: backup/standby use only, short-term need (construction site, event), experienced maintenance staff available, and budget is constrained. Used generator inspection checklist: (1) Hour meter reading (under 5,000 hours = low use, 5,000-15,000 = moderate, 15,000+ = high — negotiate accordingly). (2) Maintenance records — no records = assume worst case. (3) Load bank test results — should hold rated output without excessive exhaust smoke or temperature rise. (4) Coolant and oil analysis ($50-100 test) — reveals internal wear. (5) Transfer switch condition. (6) Fuel system inspection for algae/corrosion. Pricing guide: used generators typically sell for 30-60% of new price depending on hours, condition, and brand. Caterpillar, Cummins, and Kohler hold value best. Avoid generators that have been rental fleet units — they often have high hours with inconsistent maintenance.