VanLife Off Grid Solar Sizing Calculator

📖 Overview

This calculator translates appliance plans into battery and panel sizing numbers you can buy.

It accounts for system losses and local sun availability so off grid setups are less likely to fail in real use.

🧪 Example Scenarios

Use these default and higher-pressure example inputs to explore how sensitive this calculator is before using your real numbers.

ExampleExample: using daily appliance load (wh) = 1900, system loss factor (%) = 20, battery autonomy days = 2, peak sun hours per day = 4.5 gives you a fast baseline before testing your own numbers.

Input	Base Case	Higher Pressure Case
Daily Appliance Load (Wh)	1,900	2,185
System Loss Factor (%)	20	24
Battery Autonomy Days	2	2.4
Peak Sun Hours Per Day	4.5	5.4
Panel Wattage (W)	100	115

⚙️ How It Works

Sizes off-grid systems by converting daily load into adjusted energy demand then mapping that demand to battery reserve and panel count.

The Formula

Adjusted Load = Daily Wh × (1 + Loss %) | Panels ≈ Adjusted Load ÷ (Sun Hours × 0.8 × Panel Wattage)

Daily Load	Total planned appliance energy per day in Wh
Loss Factor	Percent inefficiency across inverter wiring and conditions
Autonomy Days	Days of battery backup required without charging
Peak Sun Hours	Usable daily solar generation window
Panel Wattage	Rated power of each panel module

💡Designing for shoulder-season sun hours instead of summer peak hours usually avoids underbuilt systems.

Quick Reference

Adjusted Daily Load	Sun Hours	Array Needed	100W Panels
1,200 Wh	5.0	~300W	3
2,100 Wh	4.5	~583W	6
3,000 Wh	3.8	~987W	10

When To Use This

Use this tool when you need a fast decision during active planning or execution.
Use this before committing money, time, or tradeoffs that are hard to reverse.
Use this to compare options using the same assumptions across scenarios.

Edge Cases To Watch

Results can be misleading if key inputs are missing, stale, or unrealistic.
Very small or very large values may amplify rounding effects and interpretation risk.
If assumptions change mid-decision, recalculate before acting.

Common Mistakes

Mixing units or time periods between inputs.
Using rounded or outdated numbers when the decision depends on precision.
Reading the result without checking whether the default assumptions match your situation.

Practical Tips

💡 Validate appliance duty cycles instead of nameplate-only estimates.

💡 Add margin for winter and cloudy-day variability.

💡 Keep battery depth-of-discharge limits in your final design.

Frequently Asked Questions

❓ What is the vanlife off grid solar sizing calculator?

It is a free tool for calculating vanlife off grid solar sizing from the inputs shown on the page.

❓ Can I change the default values?

Yes. Replace the defaults with your own numbers, then rerun the calculator to compare scenarios.

❓ How should I interpret the result?

Use the result as a practical estimate for travel planning, then check the formula notes and related calculators for context.

❓ Why include an 0.8 performance factor?

Real systems lose output to temperature, wiring, controller, and panel angle effects.

❓ Does this replace full electrical design?

No. It is a planning tool and should be followed by component-level design checks.