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Off-Grid Solar System Calculator

Size your panels, battery bank, and inverter for complete energy independence

✓ Free estimate — no signup required

Off-Grid Solar: The Key Differences

Going off-grid means your solar system must supply 100% of your electricity — with no utility backup. Three components work together: panels (generation), batteries (storage), and an inverter/charger (AC conversion and battery management). Sizing all three correctly is critical.

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Oversize Panels

20–40% more than grid-tied to ensure charging in suboptimal weather

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Size Batteries

1–4 days autonomy based on your risk tolerance and climate

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Right-Size Inverter

Handle your peak simultaneous load plus battery charging

Off-grid sizing tip: Use the calculator below to get your base panel estimate, then add 25–35% to that panel count to account for battery charging overhead and worst-case weather days.

Enter your estimated monthly consumption to size your solar array

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Off-Grid System Sizing Reference

These are typical configurations for common off-grid scenarios:

ScenarioDaily kWhPanelsBattery BankAutonomy
Small Cabin / RV2–5 kWh1–3 kW10–20 kWh (LFP)2–3 days
Weekend Retreat5–10 kWh3–6 kW15–30 kWh (LFP)2–3 days
Full-Time Off-Grid Home15–30 kWh8–15 kW30–60 kWh (LFP)2–4 days
High-Consumption Off-Grid30–50 kWh15–25 kW60–100 kWh (LFP)2–3 days

LFP = lithium iron phosphate. Assumes 48V system with south-facing panels, average US sun hours, and 80% usable battery depth of discharge.

Off-Grid Solar — Frequently Asked Questions

How does an off-grid solar system differ from grid-tied?▾
In a grid-tied system, the utility grid acts as a virtual battery — you export surplus power and draw it back at night. In an off-grid system, there is no utility connection. Your panels charge a physical battery bank, and the inverter/charger draws from that bank to power your home. Off-grid systems require 20–40% more panel capacity than grid-tied systems of the same consumption, plus significant battery storage.
How do I calculate how many batteries I need for off-grid solar?▾
Start with your daily kWh consumption. Multiply by your desired autonomy days (how many days you want to run without sun). Divide by your battery's usable depth of discharge (80–90% for lithium, 50% for lead-acid). Example: 10 kWh/day × 2 days autonomy ÷ 0.85 usable = 23.5 kWh of battery capacity needed. A 200Ah 48V lithium bank provides roughly 9.6 kWh usable.
What size inverter do I need for an off-grid home?▾
Your inverter must handle your peak simultaneous load. Add up the wattage of everything you might run at once: well pump, refrigerator, microwave, lights, and a few outlets. A typical off-grid home needs a 3,000–6,000W continuous-rated inverter/charger. Brands like Victron MultiPlus, Schneider XW+, and Outback Radian are popular choices for residential off-grid systems.
Does the 30% federal solar tax credit apply to off-grid systems?▾
Yes — the federal Investment Tax Credit (ITC) applies to off-grid solar systems, including the battery storage component when charged primarily by solar. As of 2025, the ITC is 30% and extends through 2032. Battery storage added to an off-grid system (or standalone storage) also qualifies for a separate 30% credit under the IRA.
What backup generator do I need for an off-grid home?▾
A 5,000–10,000W propane or diesel generator is standard for off-grid backup. Generators handle extended cloudy periods and charge the battery bank when solar is insufficient. Most off-grid homeowners run their generator only 2–8 hours during extended cloudy stretches. Propane generators integrate well with off-grid systems because propane stores indefinitely and burns cleanly.

Related Solar Resources

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Grid-Tied Solar Calculator

Standard net-metered solar — most common and cost-effective

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Battery Backup Solar Calculator

Grid-connected with battery for outage protection

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Off-Grid Use Case Guide

Detailed considerations for fully off-grid living

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Cabin Solar Calculator

Seasonal and year-round off-grid cabin systems

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How Many Solar Panels Do I Need?

Complete sizing guide for any setup

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Main Solar Panel Calculator

Full calculator with custom inputs

Off-Grid Solar Resources by State

→California→Texas→Florida→Arizona→Nevada→North Carolina→Georgia→Colorado→New York

Disclaimer:Off-grid system sizing involves many variables beyond this calculator's scope, including battery chemistry, inverter efficiency, charge controller losses, seasonal sun variation, and load profiles. This is a planning estimate only. Consult a licensed off-grid solar installer and electrician for final system design.