DIY Off-Grid Inverter & Battery Bundles for Reliable Backup

Discover off-grid solar bundles, designed for cabins, tiny homes, remote workshops, and emergency backup. Each bundle pairs Fortress Power inverters with lithium batteries, giving you reliable, DIY-friendly energy without relying on the utility grid.

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Frequently Asked Questions

🙋 We’ve gathered the questions people ask most, so you can quickly find the answers you need.

1. How do I calculate inverter size for my solar system?

When calculating inverter size for your PV system, consider your system type and appliance power. For off-grid systems, the inverter must handle all household loads plus startup surges. For grid-tie or on-grid hybrid solar inverters, size it to match your solar array’s peak output, while the grid handles extra surges.
2. What factors should I consider when sizing an inverter for solar panels?

Check both continuous wattage (appliance running power) and peak/surge wattage (2–3× higher for motors, pumps, air conditioners, etc.). Your inverter’s continuous rating should be at least 25% above total running load, and its surge rating should cover the highest combined startup load. This ensures safe operation when sizing inverter for PV system.
3. What inverter size do I need for a 3.6 kW solar array?

Off-grid: At least a 6.5 kW inverter to cover loads and surges.
Grid-tie / on-grid hybrid solar inverter: Match to 3.6–4.0 kW, or go up to 8 kW for surge capacity and future expansion.

Not Sure What You Need?

Choosing the right solar battery depends on your energy goals, inverter, and how much backup time you need. Use our Solar System Design Tool for instant recommendations — or reach out to our support team for one-on-one help.

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