Whole-Home Solar Battery Sizing & Blackout Autonomy Calculator (2026)
Undersized solar batteries trip offline the moment a 240V well pump or 3-ton air conditioner compressor kicks on. Select your home appliances and backup mode below to compute your exact daily kWh consumption, continuous & surge inverter kW, and factory-direct UL9540 battery savings.
Home Circuits & 240V Loads
EcoFlow Delta Pro Ultra (18.3 kWh, 3x Battery) or EG4 18kPV + 2x 14.3kWh LFP
Spec: 12kW Continuous / 21.6kW Motor-Start Surge 240V · LiFePO4 (LFP) 6,000+ cycle chemistry · Zero proprietary installer lock-in.
💡 ENGINEERING FAQHow many kWh of battery storage do I need to run a 3-ton central AC during a blackout?
A 3-ton central air conditioner draws roughly 3,500W continuous running power (15 kWh per day with cycling) and requires 7,200W to 8,500W of Locked Rotor Amperage (LRA) startup surge. To back up a 3-ton AC alongside a refrigerator, lights, and Wi-Fi for 24 hours without solar recharge, you need 21.5 kWh to 28.6 kWh of LFP battery storage paired with a 12kW continuous / 18kW–21kW surge 240V split-phase hybrid inverter (such as an EG4 18kPV + 2x 14.3kWh PowerPro or dual EcoFlow Delta Pro Ultra).
💡 ENGINEERING FAQHow much battery capacity is needed for California NEM 3.0 peak rate arbitrage?
Under California's CPUC NEM 3.0 Net Billing Tariff, midday grid export credits drop to ~$0.04–$0.05/kWh while evening peak rates (4 PM – 9 PM) surge to $0.58–$0.82/kWh. Most California households consume 10 kWh to 14 kWh during that 5-hour evening peak window, making a single 12.2 kWh to 14.3 kWh LFP battery bank the mathematical sweet spot for a 4.1-year payback.
💡 ENGINEERING FAQWhy do turnkey solar installers charge $18,000–$22,000 for a single 13.5 kWh battery?
National solar installers mark up proprietary batteries by 110% to 150% to cover sales commissions and 30% lender dealer fees. Sourcing a UL9540-certified EG4 14.3kWh PowerPro + 18kPV hybrid inverter or EcoFlow Delta Pro Ultra directly from the distributor costs $7,200 to $8,500 before hiring a local licensed master electrician ($1,800–$2,500 labor), saving $9,000 to $11,500.
Skip the $14,000 Installer Markup: Direct-Purchase Hardware & Vetted Quotes
Turnkey solar salespeople routinely charge $3.60–$4.80/W by bundling 30% loan dealer fees and $12,000+ battery margins. Buying Tier-1 UL9540 hardware directly—either DIY or hiring a local licensed electrician ($1,500–$2,500)—cuts total cost by 50–65%.
EG4 18kPV Inverter + 14.3kWh PowerPro WallMount
The gold-standard UL9540 all-in-one hybrid system. Pair an 18kW PV input hybrid inverter (200A pass-through) with an indoor/outdoor IP65 14.3kWh LiFePO4 WallMount battery—saving $12,000+ vs turnkey quotes.
- 18kW PV Input / 12kW Continuous AC Output (200A Pass-Through)
- 14.3kWh LiFePO4 (8,000+ cycles @ 80% DoD)
- UL9540 & UL1741-SB Certified for Permit Approval
EcoFlow Delta Pro Ultra (6kWh–30kWh Modular)
Skip the $30,000 contractor quote and 6-month utility interconnection wait. Delivers 7.2kW–21.6kW continuous 120V/240V split-phase output and 5.6kW Solar Input right out of the box—expandable up to 90kWh.
- 7,200W–21,600W 120V/240V Split-Phase Output
- 6.1kWh LFP Stackable Battery (scales to 30kWh–90kWh)
- 5,600W Solar Input — Zero Roof Permit Required for Portable PV
Renogy 48V Off-Grid & Hybrid LFP Solar Kit
Complete modular 48V architecture combining high-efficiency N-type bifacial panels, a 48V 3,500W–5,000W MPPT inverter-charger, and smart modular LiFePO4 storage at ~$1.15/W hardware cost.
- 48V High-Efficiency Bus (75% lower copper wire loss)
- Modular 48V 50Ah / 100Ah Smart LiFePO4 Battery Bank
- Complete Plug-and-Play MPPT All-in-One Controller
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