Solar Battery Capacity Sizing Calculator
Enter your daily energy load and backup days — get required battery capacity in kWh and Ah for LFP, NMC and lead-acid chemistries side by side. Preliminary sizing for RFQ, not a substitute for engineered system design.
OmniSol sources and coordinates LFP battery modules and rack-mount ESS from manufacturers certified to IEC 62619 and UN 38.3 for residential, C&I and small utility-scale solar projects.
Load & System Parameters
Total AC load per day. Read from energy meter or sum appliance watt-hours. Residential: 5–20 kWh/day; C&I: 50–500+ kWh/day
Backup duration without solar input. 1 day is common for grid-tied hybrid; 2–3 days for off-grid with sun variability
48V and 51.2V are equivalent for LFP packs. Confirm against inverter spec
Covers battery discharge and DC-to-AC inverter losses. LFP + quality inverter: 90–95%. Lead-acid: 80–85%.
Applies chemistry-specific capacity derate: LFP 0–10°C →15% derate; LFP below 0°C →25%. Lead-acid much more sensitive.
Maximum simultaneous AC load. Used for minimum inverter continuous output sizing.
Estimates daily solar generation at ~4 peak sun hours (conservative, mid-latitude). Enter 0 to skip.
Typical DoD by Chemistry
Enter your load and system parameters and click Calculate
Results compare LFP, NMC and lead-acid side by side
LFP (LiFePO₄)
90% DoD
NMC (Li-Ion)
80% DoD
Lead-Acid (AGM/Gel)
50% DoD
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Frequently Asked Questions
How do I calculate solar battery capacity?
Required gross capacity (kWh) = (Daily energy use × Backup days) ÷ (Depth of Discharge × System efficiency). For example, 10 kWh/day for 1 day backup with LFP at 90% DoD and 92% efficiency gives 10 ÷ (0.90 × 0.92) ≈ 12.1 kWh gross. Convert to Ah by dividing gross kWh × 1000 ÷ system voltage.
What is the best battery chemistry for solar storage?
LFP (LiFePO₄) is the most widely specified chemistry for solar storage — 3,000–6,000 cycle life at 90% DoD, excellent thermal stability and no memory effect. NMC offers higher energy density but shorter cycle life. Lead-acid has lower upfront cost but only 50% usable DoD and 400–800 cycle life.
What is depth of discharge (DoD) and why does it matter?
DoD is the percentage of total capacity that can be used before recharging. LFP is typically rated at 90% DoD; lead-acid should not exceed 50% to protect cycle life. A higher usable DoD means less gross capacity required for the same backup energy.
Should I use 48V or 51.2V for my solar battery system?
48V is the nominal label; 51.2V is the actual nominal voltage of a 16-cell LFP pack (16 × 3.2V). For preliminary sizing the difference is negligible. Always confirm against your inverter's battery voltage input range.
Does OmniSol supply LFP batteries for solar projects?
Yes. OmniSol sources and coordinates LFP battery modules and rack-mount ESS for residential, C&I and small utility-scale projects from manufacturers certified to IEC 62619 and UN 38.3. Contact us with your kWh requirement and project details for a sourcing quotation.
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