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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.

Prepared by the Solar Calculator HQ editorial team. Review our formula, source and limitation standards.

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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