Should I Buy More Solar or More Battery?
Model your battery capacity, solar input, daily consumption and trip length together to see whether solar generation or battery capacity is limiting your setup.
Where's Your Bottleneck?
Estimated daily solar generation
720 Wh
Daily shortfall (battery must cover)
180 Wh
Your solar doesn't fully offset daily use, but your battery has enough usable capacity (1.9 kWh) to absorb the shortfall (180 Wh/day) across your 5-day trip. Your battery capacity is currently doing the heavy lifting — more solar would reduce how much you draw it down each day, which matters most if your trip extends beyond 5 days or sun conditions are worse than assumed.
This model compares your daily consumption against estimated daily solar generation (solar W × sun hours × 80% system efficiency) and checks whether your usable battery capacity can absorb any shortfall across your trip length. It's a planning estimate — actual weather and usage will vary.
Should I buy more solar or more battery?
It depends on your bottleneck. If your solar already covers your daily use, more battery mainly buys resilience against bad weather, not everyday balance. If your solar consistently falls short and your battery can't absorb the gap over your trip length, more solar (or reduced consumption) addresses the actual cause — extra battery alone just delays the same problem.
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Frequently Asked Questions
Is it better to oversize solar or oversize battery?+
For trips longer than a few days with regular sun, oversizing solar generally gives more day-to-day flexibility, since it reduces how much you draw the battery down daily. For short trips or unpredictable weather, more battery capacity provides a bigger buffer. Model your own numbers above to see which matters more for your situation.
What if I have no solar at all?+
Set solar wattage to 0 — the calculator will show your full daily use as the shortfall your battery alone must cover, which is the same calculation as the Off-Grid Days Calculator's 'no solar' scenario.
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