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Caravan, Motorhome & Camper Trailer Solar Calculator

Free Australian caravan solar calculator: enter daily Wh, peak sun hours and battery type — get panel wattage, battery Ah, MPPT controller and inverter size for caravans, motorhomes and camper trailers.

Caravan & Motorhome Solar Calculator

Battery capacity
867 Ah
Recommended solar wattage
720 W
MPPT controller size
80 A
Inverter rating
1,150 W

What this calculator does

This caravan solar calculator sizes a complete 12 V or 24 V off-grid system for any Australian recreational vehicle — touring caravan, camper trailer, fifth-wheeler, motorhome or self-converted van. Enter your daily energy use in watt-hours, peak sun hours, leisure battery chemistry and peak 240 V load, and it returns four numbers: battery bank capacity in Ah, solar panel wattage, MPPT controller amp rating, and inverter wattage.

Every result includes the AS/NZS 3000 125% continuous-load factor on the charge controller — the multiplier a licensed electrician applies on the installation certificate.

The four numbers every caravan solar build needs

A complete caravan solar setup is four components matched together: panels, MPPT controller, battery bank and inverter. Undersize any one and the whole rig fails: too few panels and the bank never recharges; too small a battery and you wake to a flat system; an undersized controller throttles array output; an inverter that can’t handle peak 240 V loads trips offline mid-microwave.

1. Battery capacity (Ah)

Battery Ah = (Daily Wh × Days of autonomy) ÷ (Battery V × Depth of Discharge)

For a 2,600 Wh daily load on a 12 V AGM bank at 50% DoD with 2 days of cloudy reserve: 2600 × 2 ÷ (12 × 0.50) = 867 Ah. That’s four 220 Ah Century, Giant Power or Optima AGMs wired series-parallel.

LiFePO4 changes the maths. Same 2,600 Wh, same 2 days, DoD at 80%: 2600 × 2 ÷ (12 × 0.80) = 542 Ah. Three Enerdrive ePOWER 200 Ah, two BMPRO 230 Ah, or one Itechworld 600 Ah cover it. Lithium weighs 14 kg per 100 Ah versus 30 kg for AGM — significant for ATM-compliant towing on a single-axle van. The Clean Energy Council off-grid sizing guide notes LiFePO4 cycle life of 3,000–6,000 versus 400–800 for lead-acid, putting levelised cost per cycle below AGM.

2. Solar panel wattage (W)

Panel W = Daily Wh ÷ (Peak Sun Hours × System Efficiency)

For 2,600 Wh per day at 5.2 PSH (Outback QLD/NT average): 2600 ÷ (5.2 × 0.80) = 625 W. Round up to 720–800 W. Australian PSH varies sharply: BoM data shows Darwin at 5.8 year-round, Brisbane 5.0 summer / 4.0 winter, Hobart 4.5 summer / 2.0 winter. Size for the lowest month you’ll tour.

3. MPPT charge controller (A)

Controller A = Panel W ÷ Battery V × 1.25

The 1.25 factor reflects AS/NZS 3000 Section 2.5 — continuous-load conductors and protective devices must be rated above the design current. A 720 W array on a 12 V bank needs 720 ÷ 12 × 1.25 = 75 A → 80 A MPPT (REDARC Manager30 with secondary, Enerdrive ePOWER 60 DCDC+, or Victron SmartSolar 150/85). Going to 24 V halves it: 720 ÷ 24 × 1.25 = 37.5 A → 40 A.

Always check the controller’s PV input voltage limit against the array Voc at the coldest temperature you’ll camp at. Australian Alpine routes can push panel Voc 10–15% above STC on frosty mornings.

4. Inverter (W)

Inverter W = Peak simultaneous 240 V load × 1.25

A 1,000 W microwave with an 800 W kettle and a 30 W phone charger needs 1,830 × 1.25 = 2,288 W → 3,000 W pure-sine (Enerdrive ePOWER 3000, REDARC RS3000, or Projecta 3000W). For TV, laptop and small appliances, a 1,500 W pure-sine is plenty. Pure-sine only.

Sample sizing for common Australian caravan setups

Weekend touring caravan (2,000 Wh/day, 12 V, AGM) — A retired couple in a Jayco Silverline running LED lighting, Engel 50L compressor fridge, vent fan and laptop. 2,000 ÷ (5.0 × 0.80) = 500 W → 600 W array (two 300 W panels). Battery: 2,000 × 2 ÷ (12 × 0.50) = 667 Ah → four 165 Ah Century AGMs in series-parallel. Controller: 600 ÷ 12 × 1.25 = 62.5 A → 80 A MPPT. Inverter: 1,500 W. Australian DIY parts via hipages-listed installers and Service.com.au quotes in 2025–2026: A$4,200–6,200 DIY, A$7,800–10,500 dealer-fitted.

Full-time motorhome (5,000 Wh/day, 12 V, LiFePO4) — A family in a Winnebago Cooper with a 240 V residential fridge, satellite TV, induction cooktop and instant pot. 5,000 ÷ (5.0 × 0.80) = 1,250 W → 1,400–1,600 W array. Battery: 5,000 × 2 ÷ (12 × 0.80) = 1,042 Ah LiFePO4 — five Enerdrive ePOWER 200 Ah, four BMPRO 260 Ah or two Itechworld 600 Ah. Controller: 1,600 ÷ 12 × 1.25 = 167 A — split across two 80 A MPPTs. Inverter: 3,000 W pure-sine. Installed DIY: A$11,500–16,000.

Camper trailer with off-road kit (2,800 Wh/day, 12 V, LiFePO4) — A weekend off-roader in a Trackabout XR Goliath running a Dometic fridge, LED strip lights, an Aircommand and 12 V tyre pump. 2,800 ÷ (5.0 × 0.80) = 700 W → 800 W array (200 W fixed + 200 W foldable on tow-vehicle bonnet + 400 W solar blanket). Battery: 2,800 × 2 ÷ (12 × 0.80) = 583 Ah LiFePO4 — two Enerdrive 300 Ah or three 200 Ah modules. Controller: 800 ÷ 12 × 1.25 = 83 A → 100 A or split 2 × 60 A MPPT. Inverter: 1,500 W for occasional kettle. A$6,400–9,500 DIY.

Wiring and code references (Australia)

Australian caravan solar must comply with:

  • AS/NZS 3001 — Electrical installations — connectable installations and caravan sites. Covers 240 V side of caravans, motorhomes and registered campers.
  • AS/NZS 3000 — Wiring Rules. Sections 2.5 (continuous loads) and 5.6 (overcurrent protection) drive the 125% factor and cable sizing.
  • AS/NZS 5033 — Installation and safety requirements for photovoltaic arrays. Conductor sizing, string fusing, plug/socket isolation.
  • AS/NZS 4509.2 — Stand-alone power systems design. Used for cabin and full off-grid; the principles apply to caravans.

DC-side cabling, MPPT controllers and battery banks can be DIY but must follow AS/NZS 3000 / 5033 conductor sizing — use the solar panel wire size calculator. Any 240 V wiring, inverter hard-install, AC bus and RCD work in a registered caravan must be done by a licensed electrician (state-specific license).

Common Australian caravan solar mistakes

  • Sizing for Darwin in July (5.5 PSH) when touring Hobart in June (2.0 PSH). The same array delivers a third as much energy. Size for the lowest PSH you’ll camp in.
  • Mixing battery ages. Adding a new AGM to an existing string drags the new battery down to the old one’s capacity within months. Replace whole banks.
  • Skipping the 125% AS/NZS factor. A 60 A MPPT exactly matched to a 720 W array on 12 V (60 A nominal) thermally cycles and fails within a year of regular outback use.
  • Wiring panels in parallel only. Two 12 V panels in parallel produce 12 V × 16 A — that pushes cable size to 16 mm² over a 5 m roof run. The same panels in series at 24 V draw 8 A and run cleanly on 6 mm².
  • Using a non-LiFePO4-profile MPPT with lithium batteries. AGM, gel and LiFePO4 have different bulk/absorb/float voltages. Use a controller and converter with explicit lithium profile (Victron, Enerdrive, REDARC) or halve the battery life.

Sources

Frequently asked questions

How many watts of solar do I need on my caravan in Australia?
An average Australian touring caravan with LED lighting, a 12 V compressor fridge (Engel/Waeco/CFX), an Aircommand vent fan and 12 V outlets draws 2,200–2,800 Wh per day. At Outback Queensland averages of 5.2–6.0 peak sun hours, that needs 530–675 W of panels with an 80% efficiency factor — most rigs run a 600–800 W rooftop array. Full-time travellers running a 240 V residential fridge, microwave and an inverter air-con push 5,000–8,000 Wh and need 1,500–2,400 W. Clean Energy Council off-grid guidance suggests adding a 20% buffer for the winter southern states (VIC/TAS) where June PSH drops to 2.0.
What size battery for caravan solar in Australia?
Battery capacity in amp-hours equals daily Wh times days of autonomy, divided by battery voltage times depth-of-discharge. For 2,600 Wh daily on a 12 V AGM bank at 50% DoD with 2 days of cloudy reserve: 2600 × 2 ÷ (12 × 0.50) = 867 Ah. Switching to LiFePO4 at 80% DoD: 542 Ah. Most Australian caravan builds now run a single Enerdrive ePOWER 200 Ah lithium, an Itechworld 240 Ah or two BMPRO 100 Ah LiFePO4 instead of four 110 Ah Century or Giant Power AGMs — the 30 kg-per-100Ah weight saving matters for ATM-compliant towing.
MPPT or PWM controller for Australian caravans?
MPPT for any array above 200 W. Australian caravan solar is dominated by 60-cell and 72-cell monocrystalline panels (Enerdrive, Projecta, REDARC, Renogy AU) that produce 18–24 V open-circuit — well above the 12 V battery target. A PWM controller throws away 25–30% of array output as heat by pulling panel voltage down to battery voltage. A REDARC Manager30 MPPT, Enerdrive ePOWER 40DC+ DCDC charger, or Victron SmartSolar 100/30 MPPT recovers that loss at 96–97% efficiency. Price gap: $180–350 for a 30 A MPPT versus $80–140 for PWM.
How big an inverter for caravan use?
Size to the largest simultaneous 240 V load times 125% (AS/NZS 3000 continuous-load factor). A 1,000 W microwave running with an 800 W kettle needs 1,800 × 1.25 = 2,250 W — fit a 3,000 W pure-sine inverter (Enerdrive ePOWER 3000, REDARC RS3000, or Projecta 3000 W). For laptop, TV and 12 V appliances, a 1,000–1,500 W pure-sine handles it. Pure-sine only — modified-sine waveforms damage CPAP machines, induction cooktops and modern compressor fridges.
Does caravan solar work year-round in Australia?
Yes in most of the country. Cairns and Darwin run 5.0–6.5 PSH year-round. Sydney and Brisbane average 4.5 PSH in winter, 5.5 in summer. Hobart and southern VIC drop to 2.0–2.5 PSH in June — owners touring south in winter need to oversize 30–50% or accept that EHU/genset top-up will be needed on cloudy days. Bureau of Meteorology solar exposure data (table at /calculators/solar-irradiance-calculator/) gives precise PSH figures by post code and month.
Do I need an REC-accredited installer for caravan solar?
Caravan and motorhome 12 V/24 V solar work is exempt from REC accreditation requirements — those apply to grid-connected installations under the Small-scale Renewable Energy Scheme. However, AS/NZS 3001 (Electrical installations — connectable installations and caravan sites) governs the 240 V side: any AC wiring, inverter installation, EHU lead and RCD work in a registered caravan or motorhome must be done by a licensed electrician. DC-side solar wiring, MPPT controllers and battery banks can be DIY but should follow AS/NZS 3000 and AS/NZS 5033 conductor sizing and overcurrent protection.

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