Whole Home Backup vs Partial Backup: What You Need

Whole-Home Backup

Power output determines whole-home capability. Read our Tesla Powerwall 3 review for specs.

Whole-home battery backup systems are designed to power everything in your house during a grid outage, just as if the utility were still delivering electricity. This means your air conditioner, electric dryer, oven, pool pump, and every light and outlet continue operating normally. Achieving this capability requires substantial battery capacity and power output, making whole-home backup the most expensive configuration.

A typical whole-home backup system requires 20 to 40+ kWh of battery storage and an inverter capable of delivering 10 to 20 kW of continuous power. For reference, a central air conditioner alone draws 3 to 5 kW when running, and an electric water heater pulls 4 to 5 kW. Powering these high-demand appliances simultaneously requires significant battery capacity.

Costs for whole-home backup range from $15,000 to $30,000+ after federal tax credits, depending on home size and electrical loads. While expensive, whole-home backup provides complete lifestyle continuity during outages, eliminating any need to change behavior or sacrifice comfort.

Partial Backup (Essential Loads)

Battery capacity determines backup duration. Understand battery degradation.

Partial backup focuses on powering only critical circuits during an outage, reducing required battery capacity and cost significantly. A typical essential loads backup system provides 10 to 15 kWh of storage and 5 to 8 kW of power output, sufficient for maintaining safety, communication, food preservation, and basic comfort.

Partial backup requires installing a dedicated "essential loads panel" (also called a critical loads panel or backed-up loads panel). Your electrician moves selected circuits from your main panel to this new panel, which receives battery power during outages. Only these selected circuits remain powered; everything else goes dark.

Most homeowners find partial backup provides the best value, covering truly important needs while avoiding the high cost of whole-home systems. With smart load management, even smaller partial backup systems can provide meaningful comfort during extended outages.

Typical Essential Circuits

Circuits commonly included in partial backup configurations:

• Refrigerator and freezer: 150-300W running, essential for food preservation
• Some lighting: LED circuits in kitchen, bathroom, bedroom, living areas
• Internet and router: 10-20W, critical for communication
• Medical equipment: Any required medical devices
• Furnace blower or heat pump: 500-1,500W for climate control
• Well pump: 1,000-2,000W (surge), essential for water supply
• Security system: 20-50W for safety monitoring
• Phone charging outlets: Select outlets for device charging

Comparison

Load Management Strategies

Smart load management can extend partial backup runtime significantly:

Stagger Usage: Run the refrigerator for an hour, then the microwave, then the well pump. Avoid running multiple high-draw appliances simultaneously.

Propane Alternatives: Using propane for heating, cooking, and water heating eliminates major electrical loads, extending battery backup for truly essential circuits.

Smart Panels: Advanced electrical panels like Span automatically manage loads during outages, temporarily shedding non-essential circuits to extend backup duration.

Hybrid Approaches

Some homeowners choose a middle path between whole-home and minimal partial backup:

• Medium backup (15-20 kWh): Powers essentials plus one high-draw appliance like AC
• Generator + battery hybrid: Battery handles brief outages; generator starts for extended events
• Expandable systems: Start with partial backup and add batteries later as budget allows

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Making Your Decision

Choose whole-home backup if:

• Budget is not a primary constraint
• You experience frequent multi-day outages
• Medical needs require continuous full power
• You work from home and need uninterrupted full power

Choose partial backup if:

• You want backup power at reasonable cost
• Outages are typically brief (under 24 hours)
• You can adapt behavior during outages
• Daily rate arbitrage value is also important

Most homeowners find that partial backup provides the optimal balance of outage protection and cost-effectiveness. With thoughtful circuit selection and load management, a modest battery system can maintain comfort and safety during the vast majority of grid outages.