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Generator Basics
ENERGY
GENERATOR = GUARANTEED POWER: When sun isn't shining and batteries are low, a generator delivers. But it burns fuel, makes noise, and needs maintenance.
Goal: Right-sized backup that runs when needed, sips fuel, and lasts for years.
Generator Types
Gasoline
- Power range: 1kW portable to 10kW+ stationary
- Fuel availability: Everywhere, but stores poorly (6-12 months max)
- Cost: Cheapest to buy ($300-2000 portable)
- Runtime: 8-12 hours per tank typical
- Noise: Loud unless inverter type
Gasoline degrades. Add stabilizer when storing. Rotate fuel supply annually.
Propane
- Power range: 2-20kW+
- Fuel availability: Tanks delivered, stores indefinitely
- Cost: Moderate ($500-3000)
- Runtime: Depends on tank size. 20lb grill tank = 2-5 hours. 100 gallon = days.
- Noise: Similar to gas
Propane never goes bad. Best fuel for long-term backup. Large tank = weeks of runtime.
Diesel
- Power range: 5-50kW+ (industrial sizes common)
- Fuel availability: Gas stations, fuel distributors
- Cost: Expensive ($2000-10000+)
- Runtime: Large tanks common. 12-24 hours per fill typical.
- Noise: Loudest, but enclosed units available
Diesel engines last longest (10,000+ hours). Best for frequent use. Fuel stores 1-2 years with treatment.
Dual/Tri-Fuel
- Power range: 3-10kW typical
- Fuel flexibility: Gasoline + propane, or gas + propane + natural gas
- Cost: Moderate ($500-2500)
- Runtime: Depends on fuel choice
Best of all worlds. Run on propane for storage, switch to gas if propane runs out. Conversion kits available for many generators.
Inverter Generators
- Technology: Produces DC, inverts to clean AC
- Power range: 1-4kW typical (larger available)
- Benefits: Quiet, fuel-efficient, clean power for electronics
- Cost: Premium ($500-2000)
Honda EU series is the gold standard. Predator, Champion, Westinghouse offer good value alternatives.
Quick Comparison
| Type | Cost | Fuel Life | Runtime/Tank | Best For |
|---|
| Gasoline | Low | 6-12 mo | 8-12 hrs | Occasional use, budget |
| Propane | Medium | Forever | Varies | Long-term backup |
| Diesel | High | 1-2 yrs | 12-24 hrs | Frequent/heavy use |
| Dual-fuel | Medium | Propane store | Varies | Flexibility |
| Inverter | High | Gas/propane | 8-20 hrs | Electronics, quiet |
Sizing Your Generator
Calculate Running Load
Add up watts of everything you want to run simultaneously:
- Refrigerator: 150-400W running
- Freezer: 150-400W running
- Lights: 10-100W total
- Phone chargers: 10-30W each
- Furnace fan: 300-800W
- Well pump: 500-1500W
- Microwave: 1000-1500W
- Window AC: 500-1500W
Running watts = Sum of all devices you'll use at once
Account for Surge
Some devices need 2-3x their running watts to start:
- Refrigerator/freezer: 2-3x running watts for 1-3 seconds
- Well pump: 2-3x running watts
- Air compressor: 3-5x running watts
- Power tools: 2-4x running watts
Surge capacity needed = Highest surge in your list
Generators have two ratings: Running watts (continuous) and Starting watts (surge for seconds). Size for running, verify surge covers your biggest startup.
Sizing Examples
Essentials only (2000W): Fridge, lights, phone chargers, furnace fan. Portable inverter works.
Comfort backup (5000W): Above + freezer, microwave, TV, window AC in one room.
Whole house (10,000W+): Everything including well pump, electric water heater, multiple AC units.
Run Schedule
For Battery Charging
When solar can't keep up, run generator to charge batteries efficiently:
- Load: Run generator at 50-75% rated load for best efficiency
- Duration: Run long enough to complete bulk charge (2-4 hours typical)
- Timing: Run during battery bulk phase, not during absorption/float
- Frequency: Only when batteries drop to 50% (lead-acid) or 20% (lithium)
Generator is most efficient at 50-75% load. Running at 10% load wastes fuel. Run hard, then shut off.
For Direct Power
During extended outages, run generator in blocks:
- Morning block: 2-3 hours. Run fridge, freezer, charge devices, run well pump to fill pressure tank
- Evening block: 2-3 hours. Cook dinner, run fridge/freezer again, charge devices
- Overnight: Shut off (unless medical equipment or heating needs it)
6 hours of runtime per day can keep essentials going for weeks on modest fuel supply.
Fuel Storage & Rotation
Gasoline
- Shelf life: 6-12 months with stabilizer
- Storage: Approved containers only (5-gallon cans common)
- Rotation: Use in car, refill cans. Every 6 months minimum.
- Stabilizer: Add STA-BIL or similar when storing. Extends life to 12 months.
NEVER store gasoline inside living space. Garage with ventilation or shed. Keep away from ignition sources.
Propane
- Shelf life: Indefinite. Never goes bad.
- Storage: 20lb grill tanks, 30lb RV tanks, 100lb cylinders, 100+ gallon tanks
- Rotation: Not needed. Tanks can sit for years.
- Safety: Store outdoors, away from ignition sources. Tanks have pressure relief.
Five 20lb tanks = roughly 15-25 hours of runtime for 3000W generator. Scale to your needs.
Diesel
- Shelf life: 12-24 months with biocide and stabilizer
- Enemy: Algae grows in diesel. Water contamination causes problems.
- Storage: 5-gallon cans to 55-gallon drums to bulk tanks
- Rotation: Use in diesel vehicle or equipment. Treat annually.
Diesel farms often have 100+ gallons on hand. Add biocide when storing, test periodically.
Exhaust Safety
CARBON MONOXIDE KILLS: Generator exhaust contains CO. You cannot see or smell it. Running a generator indoors or near open windows can be fatal in minutes.
ALWAYS: Run generators outdoors, at least 20 feet from any building opening. Point exhaust away from structures.
Safe Placement
- Outdoors only: Never in garage (even with door open), basement, or enclosed space
- Distance: Minimum 20 feet from windows, doors, vents
- Exhaust direction: Point away from buildings and people
- Weather: Protect from rain/snow but don't enclose. Canopy or generator tent is OK.
- CO detector: Install battery-powered CO detector in home as backup warning
Maintenance
Before Each Use
- Check oil level
- Check fuel level
- Inspect for leaks, damage
- Verify exhaust area is clear
Monthly (When Stored)
- Run generator for 15-30 minutes under load
- Keeps fuel fresh in carburetor
- Lubricates internal parts
- Verifies it works when you need it
"Exercise" your generator monthly. Generators that sit for months often won't start when needed.
Annual Service
- Change oil (typically after 50-100 hours or annually)
- Replace spark plug
- Clean or replace air filter
- Check fuel filter
- Inspect fuel lines for cracks
DIY: Most generator maintenance is simple. Oil change, spark plug, air filter. Keep spare parts on hand.
Common Mistakes
- Undersizing: Generator can't handle startup surge, trips breaker or stalls
- Running indoors: CO poisoning. This kills people every year.
- Bad fuel: Old gas gums up carburetor. Generator won't start when needed.
- No exercise: Sitting for months = stuck valves, gummed carb, dead battery (electric start)
- Overloading: Running more than rated watts shortens life, can damage appliances
- Backfeeding: Plugging generator into house outlet without transfer switch = illegal, dangerous, kills lineworkers
- Wrong extension cord: Too thin or too long = voltage drop, damaged equipment, fire risk
Transfer Switch Basics
Why You Need One
To power your house panel from a generator, you need a transfer switch. It prevents backfeeding the grid (killing lineworkers) and isolates generator power from utility power.
- Manual transfer switch: Flip switch to choose grid or generator. $300-600 + installation.
- Interlock kit: Slide plate prevents both main and generator breaker on simultaneously. $50-150 + installation.
- Automatic transfer switch: Detects outage, starts generator, switches over automatically. $500-2000 + installation.
Backfeeding (generator into wall outlet) is illegal and dangerous. It energizes the grid side of your panel and can kill utility workers repairing lines.
Checklists
Before Outage Season
- [ ] Run generator 30 minutes under load
- [ ] Change oil if due
- [ ] Check/clean air filter
- [ ] Verify fuel supply (fresh gas or propane full)
- [ ] Test with actual loads you'll use
- [ ] Confirm extension cords are correct gauge
- [ ] Stock spare oil, spark plug, air filter
Before Starting
- [ ] Generator outdoors, 20+ feet from openings
- [ ] Exhaust pointed away from buildings
- [ ] On dry, level surface
- [ ] Oil level checked
- [ ] Fuel valve on (if equipped)
- [ ] Choke set (cold start)
- [ ] Loads disconnected until running
During Extended Run
- [ ] Check oil every 8-12 hours
- [ ] Refuel when cool (not while running)
- [ ] Monitor for overheating, unusual sounds
- [ ] Keep exhaust area clear
- [ ] Rotate loads to avoid overloading
Scenario Drills
Generator won't start
- Check fuel level and fuel valve
- Check oil level (low oil shutoff)
- Try fresh fuel if gas is old
- Check spark plug connection
- Check choke position
- Pull cord slowly until resistance, then pull firmly
- If electric start, check battery
Generator runs but no power
- Check circuit breaker on generator
- Verify outlets aren't GFI tripped
- Check extension cord connections
- Test with different load (light bulb)
- If inverter type, may need reset - check manual
Generator surging or hunting
- Likely fuel issue - check for water or debris in fuel
- Try fresh fuel
- Check air filter (clogged filter = rich mixture)
- Carburetor may need cleaning (old fuel varnish)
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