Battery Education · Backup Configuration
Whole-Home vs.
Partial Battery Backup
Most homeowners don't need to back up their entire home — and most can't afford to. Here's the honest breakdown of what each option protects, what it costs, and how to decide what's right for your Fresno home.
Partial Backup
Critical loads only
A critical load panel is installed alongside your main panel. During an outage, the battery powers only the circuits in the critical load panel — typically refrigerator, lights, outlets, and medical equipment.
What it backs up
- Refrigerator and freezer
- LED lighting (selected circuits)
- Outlets for phones, laptops, medical equipment
- Router and internet
- CPAP or other medical devices
What it does NOT back up
- −Central air conditioning
- −Electric range or oven
- −Electric water heater
- −Clothes dryer
- −EV charging
Whole-Home Backup
Everything including AC
The battery system is sized and configured to power your entire home during an outage — including central air conditioning, kitchen appliances, and all other loads.
What it backs up
- Everything in partial backup, plus:
- Central air conditioning
- Electric range (limited use)
- All lighting and outlets
- EV charging (reduced speed)
What it does NOT back up
- −Electric water heater (too high draw)
- −Electric dryer (too high draw)
- −Multiple heavy loads simultaneously
How a Critical Load Panel Works
A critical load panel (also called a backup load panel) is a subpanel installed alongside your main electrical panel. During normal operation, it functions like any other subpanel — circuits in it are powered by the grid like everything else. During an outage, the battery system disconnects from the grid and powers only the critical load panel.
The circuits you put in the critical load panel are your choice. We work with you during the design phase to identify which circuits matter most. Typical selections:
Always Include
- • Refrigerator circuit
- • Kitchen outlets (GFCI)
- • Master bedroom outlets
- • Hallway lighting
- • Router/modem outlet
Usually Include
- • Living room outlets
- • Home office circuit
- • Bedroom lighting
- • Bathroom outlets
- • Garage door opener
Optional (sizing dependent)
- • Window AC circuit
- • Mini-split circuit
- • EV charger (reduced)
- • Outdoor lighting
- • Security system
Our Recommendation for Most Fresno Homeowners
For most Fresno, Clovis, and Madera homeowners, we recommend starting with partial backup (one Powerwall 3 + critical load panel) paired with solar. Here's why:
- Partial backup covers the loads that matter most during an outage — food preservation, lighting, medical equipment, and communication.
- With solar recharging, one Powerwall 3 provides indefinite backup for essential loads — even during a 5-day PSPS event.
- You can always add a second Powerwall later if you want whole-home backup capability.
- The exception: if you or a family member has a medical condition that requires air conditioning, whole-home backup with AC capability is worth the additional investment.
Frequently Asked Questions
What is the difference between whole-home and partial battery backup?
Partial backup powers only selected "critical loads" — circuits you designate as essential (refrigerator, lights, outlets, medical equipment). Whole-home backup powers everything in your home, including central air conditioning, electric range, and other heavy loads. Partial backup requires less battery capacity and costs less. Whole-home backup requires more capacity and costs more, but provides complete protection.
What is a critical load panel?
A critical load panel (also called a backup load panel or essential load panel) is a subpanel that contains only the circuits you want backed up during an outage. When the grid goes down, the battery powers only the circuits in this subpanel — not the whole home. This allows a smaller battery to provide longer backup time for the most important loads.
How do I decide which loads to put on my critical load panel?
We recommend prioritizing: refrigerator and freezer (food preservation), lighting (safety and comfort), outlets for phone charging and medical equipment, router and internet, and any medical devices. Secondary priorities include window AC units, fans, and entertainment. Central AC, electric range, and water heater are typically excluded from partial backup due to their high power draw.
Can I upgrade from partial to whole-home backup later?
Yes. If you start with partial backup and want to add whole-home capability later, you can add battery capacity (additional Powerwall units, for example) and reconfigure the critical load panel to include more circuits. We design systems with future expansion in mind.
Does whole-home backup require a larger battery in Fresno?
Yes — significantly. Essential loads in a Fresno home typically draw 0.5–1 kW. Whole-home loads including central AC draw 4–8 kW. For whole-home backup with AC in Fresno's summer heat, we typically recommend 2–3 Tesla Powerwall 3 units (27–40.5 kWh) or equivalent capacity.
What is the cost difference between partial and whole-home backup?
Cost depends on your existing system, electrical panel, and the specific battery configuration that fits your home. We provide a free, itemized quote — contact us to schedule your free assessment.
Let's Size Your Backup System
We assess your home's energy usage and backup priorities and design the right system. Free assessment in Fresno, Clovis, Madera, and 70+ Central Valley communities. Licensed contractor #1063682.
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