How to Set Up Solar on Your RV or Caravan: A Complete NZ Guide

Going off-grid in your RV or caravan means never hunting for powered sites again. A well-designed solar setup gives you reliable power for days at a time — whether you're parked on a remote beach or deep in the back country. This guide walks you through every component, how to size your system, and how to avoid the most common mistakes.

Why Solar Makes Sense for New Zealand Travellers

New Zealand's campervanning and caravanning culture is built around freedom camping — and solar is what makes that freedom real. NZ gets excellent solar irradiance, especially in the South Island and during summer months. Even in winter, a properly sized system will keep your essentials running without ever touching shore power.

The Four Core Components

1. Solar Panels

Monocrystalline panels are the standard choice for RVs — they're more efficient per square metre than polycrystalline, which matters when roof space is limited. A typical campervan or caravan setup runs between 200W and 400W total. Common configurations:

• 100–200W — suits a fridge, lighting, phone charging, and occasional laptop use
• 200–300W — comfortable for extended stays with moderate appliance use
• 300W+ — suits larger battery banks, air circulation fans, and heavier loads

Rigid panels are the most efficient and durable for permanent roof mounts. Flexible or blanket-style solar panels work well for temporary setups or where a rigid mount isn't practical.

2. MPPT Solar Controller

The solar controller sits between your panels and your battery bank, regulating the charge. Always choose an MPPT (Maximum Power Point Tracking) controller over a PWM — MPPT extracts significantly more power from your panels, particularly in partial shade or during morning and afternoon hours when the sun angle is low.

Key things to match when sizing your controller:

• Current rating — should handle your total panel wattage divided by your battery voltage (e.g. 300W ÷ 12V = 25A, so a 30A controller is the minimum)
• Voltage input — must accept your panel's open-circuit voltage (Voc), with headroom for cold temperatures which raise Voc
• Battery compatibility — must support LiFePO4 charging profiles if you're using lithium batteries

3. Battery Bank

This is where the biggest upgrade in RV power has happened over the last few years. Lithium iron phosphate (LiFePO4) batteries have largely replaced AGM as the go-to choice for serious travellers, and for good reason:

• Usable capacity — lithium gives you 80–100% usable capacity vs 50% for AGM. A 100Ah lithium battery is effectively equivalent to a 200Ah AGM.
• Weight — roughly half the weight of AGM for the same usable capacity
• Cycle life — 2,000–4,000+ cycles vs 400–500 for AGM
• Charge acceptance — lithium charges much faster and more efficiently from solar

For most campervan or caravan setups, a 100Ah LiFePO4 battery (or two in parallel for 200Ah) is a solid starting point. If you run a compressor fridge 24/7 and spend multiple consecutive cloudy days off-grid, 200Ah+ is worth considering.

4. Inverter (If You Need 240V)

If you need to run 240V appliances — laptop chargers, coffee machines, hair dryers — you'll need an inverter. Pure sine wave inverters are strongly preferred over modified sine wave; they're compatible with all appliances and won't cause issues with sensitive electronics or motor-driven loads.

Size your inverter for your peak load, not your average load. A 1,000W inverter handles most light appliances; 2,000W covers heavier loads like microwave or electric kettle use.

How to Size Your System

Sizing a solar system comes down to a simple calculation: how much power do you consume per day, and how much can your panels realistically generate?

Step 1 — Calculate your daily consumption
Add up the watt-hours (Wh) used by each appliance. For example:

• Compressor fridge (60W average): 60W × 24h = 1,440Wh/day
• LED lighting (20W): 20W × 4h = 80Wh/day
• Laptop (45W): 45W × 2h = 90Wh/day
• Phone charging: ~30Wh/day
• Total: ~1,640Wh/day

Step 2 — Factor in NZ solar hours
New Zealand averages 4–5 peak sun hours per day across the year (more in summer, fewer in winter). Using 4 hours as a conservative figure: to generate 1,640Wh/day you need 1,640 ÷ 4 = 410W of panels. In practice, system losses (heat, wiring, controller efficiency) mean you'd want 300–350W minimum for this load, accepting that cloudy days will draw down your battery.

Step 3 — Size your battery for autonomy
Your battery should hold at least 2 days of consumption without solar input — a buffer for cloudy weather. For 1,640Wh/day × 2 = 3,280Wh. At 12V: 3,280 ÷ 12 = 273Ah of usable capacity. With lithium (100% usable), that's roughly 280Ah of LiFePO4 battery.

Installation Tips

• Cable sizing matters — undersized cables cause voltage drop and heat. Use a cable size calculator and always err larger, especially on the battery-to-inverter run.
• Fuse everything — every cable run should be fused as close to the battery as possible
• Shade kills output — even partial shading on one panel can reduce output dramatically. Consider panel placement carefully, and use an MPPT controller with independent string tracking if shading is unavoidable.
• Mount panels flat or angled — a 10–15° tilt improves output and allows rain to clean the surface. Fixed roof mounts work well for most NZ travel.
• Monitor your system — a battery monitor (shunt-based) gives you accurate state-of-charge data. Guessing your battery level leads to either leaving energy on the table or unexpected flats.

Common Mistakes to Avoid

• Undersizing the battery — people often buy enough panels but skimp on battery storage. The battery is where your night-time and cloudy-day power comes from.
• Using a PWM controller with lithium batteries — most PWM controllers don't have LiFePO4 profiles and will charge incorrectly
• Mismatched components — your controller must be rated for your panel voltage and battery type. Check the specs carefully before buying.
• No battery management system (BMS) — all quality LiFePO4 batteries include a built-in BMS, but verify this before buying

Ready to Build Your System?

Viaggo stocks a curated range of quality solar and power components suited to New Zealand's RV and marine markets — including Sphere solar panels, Enerdrive MPPT controllers and inverters, Victron SmartSolar controllers, and LiFePO4 battery options from Victron, Enerdrive B-Tec, and Projecta. Everything you need for a complete, reliable off-grid setup.

If you're not sure where to start or want help speccing your system, get in touch at enquiries@viaggo.co.nz — we're happy to help you put together the right kit for your setup.