Designing the right 12V caravan or camping solar setup ensures you can reliably power fridges, lights, pumps, Starlink, CPAP machines, laptops, fans, TV systems, and more — even on long off-grid trips.
This guide walks you through exactly how to size your panels, batteries, DC-DC charger, solar controller and inverter for a safe and efficient off-grid system.

Whether you’re setting up a caravan, 4WD canopy, camper trailer, motorhome, or off-grid shed, this article gives you a step-by-step method for sizing your entire system correctly.

1. Step 1 — List Your Daily Power Usage (Watts & Amp-Hours)

Start by listing everything you want to run:

• 12V fridge

• LED lights

• Water pump

• Phone/tablet chargers

• Starlink

• CPAP

• Fans

• TVs

• Diesel heater

• 240V appliances through the inverter (kettle, induction cooktop, coffee machine, microwave, etc.)

Calculate Daily Watt-Hours (Wh)

Use:
Watt-hours = Watts × Hours used per day

Example:

• 12V fridge (50W average × 24h) ≈ 1,200Wh/day

• Starlink (60W × 10h) = 600Wh/day

• Lights (20W × 4h) = 80Wh/day

• TV (40W × 3h) = 120Wh/day

Total daily usage ≈ 2,000Wh (2kWh)

This is your total daily energy consumption.

2. Step 2 — Convert Watt-Hours to Battery Size (Ah)

Most caravan systems are 12V, so convert Wh to Ah:

Amp-hours (Ah) = Watt-hours ÷ 12V

Example:
2,000Wh ÷ 12 ≈ 166Ah per day

Recommended Battery Capacity

To avoid damaging batteries, you size for 2+ days of autonomy, especially on cloudy days.

For 166Ah/day usage:

• 2 days = 332Ah minimum

• 3 days = 498Ah recommended for touring

Typical Battery Recommendations

LiFePO₄ is always recommended for caravan/camping due to 100% usable capacity and long cycle life.

3. Step 3 — Size Your Solar Panels (Wattage Needed)

Solar needs to replace your daily usage while also recharging the battery.

Rule of Thumb (Australia):

400W of solar ≈ 150–200Ah usable battery per day in good sun

Use This Formula:

Solar watts required = Daily Wh ÷ 4.5 (average Aussie peak sun hours)

Example:
2,000Wh ÷ 4.5 = 444W minimum solar

Real-World Performance Reminder

Panels rarely reach their rated wattage due to heat, angle, shading, and NOCT performance.

? See this guide:
Why Your 300W / 400W / 500W Solar Panel Doesn’t Always Produce Its Rated Watts
https://help-centre.starpoweradvancesolartechnology.com/support/solutions/articles/51000505520-topcon-vs-perc-vs-shingled-which-cell-tech-is-best-for-off-grid-

Recommended Solar Panel Size by Battery Bank

For caravans, fixed 500W shingled panels or 400W monocrystalline panels are ideal. For camping, use folding solar blankets.

4. Step 4 — Size Your MPPT Solar Controller

Your MPPT must support:

1. Maximum input voltage (Voc)

2. Maximum input current (A)

3. Output charging current (A) for the battery bank

MPPT Output Current Formula:

Controller Amps = Solar Watts ÷ Battery Voltage

Example:
500W solar ÷ 12V = 41.6A
→ Use a 40A or preferably 50A MPPT

? Relevant article:
Comprehensive Solar Panel Troubleshooting Guide
https://help-centre.starpoweradvancesolartechnology.com/support/solutions/articles/51000502643

5. Step 5 — Size Your DC-DC Charger (Vehicle Charging)

DC-DC chargers top up your battery while driving.

General Recommendations

• 100–150Ah battery → 25A DC-DC

• 200–300Ah → 40A DC-DC

• 400–600Ah → 40–60A DC-DC (depending on alternator & wiring)

Your DC-DC must support solar input if needed, and the alternator must be able to support the load.

6. Step 6 — Size Your Inverter (240V Appliances)

Your inverter must handle continuous load AND surge load (start-up load).

Common appliances:

Recommendations:

• Light users: 300–600W inverter

• Moderate: 1,000–1,500W inverter

• Heavy (coffee machine, induction, microwave): 2,000–3,000W pure sine wave

? See this article:
Can My Inverter Run Starlink, CPAP, Coffee Machine & Other Sensitive Loads?
https://help-centre.starpoweradvancesolartechnology.com/support/solutions/articles/51000505520

7. Example System Designs

Light Touring Setup

• 200Ah LiFePO₄

• 400W solar

• 40A MPPT

• 25A DC-DC

• 600–1,000W inverter
  → Runs fridge, lights, chargers, fan, TV

Medium Off-Grid Setup

• 300–400Ah LiFePO₄

• 600–800W solar (roof or ground deploy)

• 40–60A MPPT

• 40A DC-DC

• 1,500–2,000W inverter
  → Adds Starlink, laptops, pumps, small appliances

Heavy Full-Time Setup

• 500–600Ah LiFePO₄

• 1,000–1,500W solar

• 60A MPPT

• 40–60A DC-DC

• 2,000–3,000W inverter
  → Runs coffee machine, microwave, Starlink, induction cooktop

8. Additional Tips for Better Solar Performance

• Avoid any shading over the panel surface

• Angle panels toward the sun (north-facing in Australia)

• Keep panels clean and dust-free

• Use short, heavy-gauge cables to reduce voltage drop

• Avoid mixing different wattage/voltage panels

? Related guide:
Why Is My Solar Panel Only Producing a Fraction of Its Rated Watts?
https://help-centre.starpoweradvancesolartechnology.com/support/solutions/articles/51000502643

9. Need Help Designing Your System?

If you’re unsure about sizing your solar system, feel free to contact us through your support ticket — we’re happy to help design a setup based on your power needs.

? support@starpoweradvancesolartechnology.com