Quick Answer
Partial-home (essential circuits) backup systems cost $7,000-$12,000 installed while whole-home systems range from $12,000-$25,000. Essential-circuit setups use 10-14kW generators versus 18-26kW for whole-home coverage. Choose partial backup for budget-conscious protection; whole-home for complete lifestyle continuity during outages.
Why Backup Configuration Matters
Your generator configuration affects:
- Upfront investment (thousands of dollars difference)
- Fuel consumption during outages
- What works and what doesn’t during power loss
- Long-term operating costs
- Future expandability
Configuration Comparison Overview
| Factor | Partial Backup | Whole Home |
|---|---|---|
| Generator size | 10-14 kW | 18-26 kW |
| Equipment cost | $3,000-$6,000 | $5,000-$12,000 |
| Installation cost | $4,000-$7,000 | $6,000-$13,000 |
| Total project | $7,000-$12,000 | $12,000-$25,000 |
| Fuel consumption | Lower | Higher |
| Coverage | Selected circuits | Everything |
Essential Circuits (Partial Backup)
What’s Typically Covered
Essential circuits power critical items only:
| Circuit Type | Typical Load | Priority Level |
|---|---|---|
| Refrigerator/freezer | 600-800W | Essential |
| Lighting (selected) | 500-1,000W | Essential |
| Furnace/heat pump | 1,500-3,500W | Essential |
| Water heater (if electric) | 3,000-4,500W | Often excluded |
| Well pump | 1,000-2,500W | Essential (rural) |
| Sump pump | 800-1,500W | Essential (if present) |
| Garage door | 500-800W | Useful |
| Microwave | 1,000-1,500W | Often included |
| select outlets | 500-1,000W | As capacity allows |
What’s NOT Covered
Partial backup typically excludes:
- Central air conditioning (5,000W+)
- Electric stove/oven (3,000-8,000W)
- Electric dryer (4,000-6,000W) | Electric water heater (3,000-4,500W) | Pool equipment (1,500-3,000W) | Electric vehicle charging (7,000W+)
Transfer Switch Options
| Switch Type | Circuit Count | Cost | Best For |
|---|---|---|---|
| Manual transfer switch | 6-10 circuits | $400-$800 | Budget installations |
| Automatic transfer switch | 8-16 circuits | $600-$1,200 | Standard partial backup |
| Load-shedding switch | Variable | $800-$1,500 | Maximizes smaller generators |
Whole-Home Coverage
What’s Included
Whole-home generators power everything simultaneously:
| Load Category | Typical Demand | Included? |
|---|---|---|
| All lighting | 2,000-4,000W | Yes |
| All HVAC | 4,000-8,000W | Yes |
| All appliances | 4,000-8,000W | Yes |
| Water heater | 3,000-4,500W | Yes |
| Electric cooking | 3,000-8,000W | Yes |
| Well pump | 1,000-2,500W | Yes |
| Everything else | 2,000-4,000W | Yes |
Sizing Requirements
Whole-home generators must handle startup surges:
| Home Size | AC Size | Generator Needed | Reason |
|---|---|---|---|
| 1,500 sq ft | 3 ton | 14-16 kW | Smaller loads |
| 2,000 sq ft | 3-4 ton | 16-18 kW | Standard home |
| 2,500 sq ft | 4-5 ton | 20-22 kW | Larger home |
| 3,000 sq ft | 5 ton | 22-24 kW | Larger AC |
| 3,500+ sq ft | 5+ ton | 24-30 kW | Maximum loads |
Cost Comparison Scenarios
Scenario 1: 2,000 sq ft Home
Partial Backup (Essential Circuits Only)
| Item | Cost |
|---|---|
| 12 kW generator | $3,500 |
| 10-circuit transfer switch | $600 |
| Installation labor | $4,500 |
| Permits and fees | $400 |
| Total | $9,000 |
Whole-Home Backup
| Item | Cost |
|---|---|
| 20 kW generator | $5,500 |
| 200A transfer switch | $900 |
| Installation labor | $5,500 |
| Permits and fees | $500 |
| Total | $12,400 |
Difference: $3,400
Scenario 2: 3,000 sq ft Home
Partial Backup (Essential + Some Convenience)
| Item | Cost |
|---|---|
| 14 kW generator | $4,500 |
| 16-circuit transfer switch | $800 |
| Installation labor | $5,000 |
| Permits and fees | $450 |
| Total | $10,750 |
Whole-Home Backup
| Item | Cost |
|---|---|
| 24 kW generator | $7,500 |
| 200A transfer switch | $1,000 |
| Installation labor | $6,500 |
| Permits and fees | $550 |
| Total | $15,550 |
Difference: $4,800
Runtime and Fuel Considerations
Fuel Consumption Comparison
At typical outage loads:
| Configuration | Load % | NG (therms/hr) | Propane (gal/hr) |
|---|---|---|---|
| 12 kW partial | 60% | 1.1 | 1.1 |
| 14 kW partial | 55% | 1.2 | 1.2 |
| 20 kW whole-home | 50% | 1.8 | 1.8 |
| 24 kW whole-home | 45% | 2.0 | 2.0 |
Extended Outage Fuel Costs
For 5-day outage (120 hours):
| Configuration | NG Cost @ $1.50/thm | Propane Cost @ $3.00/gal |
|---|---|---|
| 12 kW partial | $198 | $396 |
| 20 kW whole-home | $324 | $648 |
| 24 kW whole-home | $360 | $720 |
Whole-home uses ~60-80% more fuel during extended outages
Pros and Cons Comparison
Partial Backup Advantages
- Lower upfront cost: $3,000-$8,000 savings
- Smaller footprint: Less space for unit
- Lower fuel consumption: Saves during outages
- Lower maintenance costs: Smaller engine
- May fit existing panel: No upgrade needed
Partial Backup Disadvantages
- Limited coverage: AC, cooking often excluded
- Manual choices: Decide what to power
- Lifestyle disruption: Some normalcy lost
- May need load management: Shedding during peaks
Whole-Home Advantages
- Complete coverage: Everything works normally
- Automatic operation: No decisions during outage
- Lifestyle continuity: Full normalcy maintained
- Resale value: Higher perceived value
- Future-proof: Covers additions/upgrades
Whole-Home Disadvantages
- Higher cost: Significant investment
- Larger footprint: More space needed
- Higher fuel consumption: More expensive to operate
- May need panel upgrade: Additional cost
- Oversizing risk: Inefficient if underloaded
Decision Framework
Choose Partial Backup When:
- Budget is primary concern
- Outages are infrequent and short
- AC isn’t critical (mild climate) | You’re comfortable with tradeoffs
- Panel capacity is limited
Choose Whole-Home When:
- Budget allows for full coverage
- Outages are frequent or extended
- Climate control is essential
- Lifestyle continuity is priority
- You want maximum home value
Consider Upgradability
Many systems can expand later:
| Starting Point | Upgrade Path | Cost Later |
|---|---|---|
| 12 kW partial | Add circuits | $200-$500 |
| 12 kW partial | Upgrade to 18 kW | $4,000-$6,000 |
| 14 kW + load shedding | Add managed circuits | $500-$1,500 |
| 18 kW whole-home | Upgrade to 24 kW | $3,000-$5,000 |
Related Guides
For comprehensive sizing and cost planning:
- Standby Generator Size vs Cost Estimator
- Home Standby Generator Installation Cost Calculator
- Transfer Switch Upgrade Cost Calculator
- Generator Fuel Consumption Cost Calculator
FAQ
Can I add more circuits later?
Yes, if your generator has capacity and your transfer switch supports it. Budget $200-$500 per additional circuit for labor and materials.
Will a partial backup run my air conditioner?
Most 10-14 kW generators cannot start central AC units (5,000W+ starting surge). Some 16 kW units with load management can run smaller AC systems.
What if I need AC but have a partial system?
Options include: mini-split for one room ($2,000-$4,000), window AC on generator circuit ($200-$500), or upgrade to larger generator ($3,000-$6,000).
How do I decide which circuits to include?
List your essentials: refrigeration, heat, water (if well pump), sump pump, lighting, medical equipment. Then add convenience circuits as capacity allows.
Can I mix partial and whole-home?
Some homeowners use a small standby for essentials plus a portable generator for occasional AC use. This hybrid approach costs $8,000-$10,000 total.
Will partial backup affect my home’s resale value?
Partial backup still adds value but less than whole-home. In outage-prone areas, any generator is a selling point. Whole-home systems command higher premiums.
Next Step
Use the Home Standby Generator Cost & Outage Payback Simulator to compare partial versus whole-home configurations for your specific electrical load requirements. Request quotes for both options from contractors to see actual pricing differences in your area.