In-depth FAQ Guide for Solar Panel Guide for RVs, Caravans, Vans & 4x4s

Author: Solar 4 RVs  

The questions below have been grouped into similar themes.

Click on the question and the answer will appear. To make an answer disappear click back on the question (i.e. clicking on the question toggles the answer on and off).

General Solar System Questions:

Solar cells in panels mounted on your RVs roof converts sunlight into Direct Current (DC) electricity. Batteries store this electricity, so it is ready for use at any time. An inverter can convert the DC electricity into Alternating Current (AC) electricity that you can use at your RVs power points. You do not need an inverter if you only want 12V power.

  • The biggest advantage is the independence you will acquire from not being reliant on mains power when travelling. It will give you the freedom to go wherever you want for however long you want.
  • It will add re-sale value to your RV.
  • Solar power is quiet unlike generators.
  • You will save money by avoiding tourist/caravan park fees for powered sites. With electricity prices continually rising so will tourist/caravan park fees. With solar power you have the option of a less expensive unpowered site or staying at a more remote location.
  • If you enjoy quiet locations without a crowd then solar power will let you enjoy outback isolation while still enjoying all your RV luxuries.
  • You can contribute to reducing the impacts of fossil fuel power stations such as greenhouse gas emissions and air pollution.
  • The components are long lasting, durable and low maintenance. For example, solar panels typically produce energy for at least 25 years with no maintenance other than the occasional clean off with water.
  • Australian has the highest solar radiation per square metre of any continent and consequently some of the best solar energy resource in the world (GeoScience Australia

Generally yes, although it does depend on where and when you use your caravan/ RV (location of travel and time of year) and how much power you consume each day.

Sizing the system for the worst-case scenario of an average winter day in Launceston is unlikely to be cost effective or practical. There is a greater than five-fold difference in the amount of solar energy per unit area between an average sunny summer day in Geraldton and an average winter day in Launceston. In Melbourne for example, an average summer day has more than three times the solar energy per unit area in mid-summer than in mid-winter. This is based on insolation data (solar intensity over a day) generated by a computer model held by the Bureau of Meteorology ( Data for a number of places, around Australia, including Geraldton, Launceston and Melbourne, is available from Sustainability Victoria.

We have designed a Solar Power Estimate Calculator (SPEC) that lets you work out how much electricity you would regularly use and what your power needs are. Based on this we recommend a solar system kit that meets your consumption needs. Go to the ‘Assess your needs’ page of this website.

No. Solar systems (photovoltaic arrays) convert sunlight into electric current to operate appliances and lights. This is different to the products with solar thermal panels that involve water circulating through tubes to be heated by the sun for water heating.

Solar panels take light from the sun and make electricity. Solar hot water systems take heat from the sun to heat water.

Solar 4 RVs can provide complete solar power kits with all-you-need for installation including:

  • Solar panels to collect the sun’s rays. The solar panels are connected together and the output from the panels is fed into batteries via a solar charge controller.
  • A solar charge controller (sometimes also called a solar regulator) converts the solar power from the panels to charge the batteries. Some also display how much power is being generated throughout the day.
  • Batteries that store the solar power ready for when you need it. At night solar panels will not produce any electricity as they require sunlight, so batteries store the electricity allowing you to use it when you want, such as in the evenings.
  • An inverter that converts battery voltage to 240 volts so it can be used at your power points. Some also provides information such as the amount of power being used.
  • Installation components such as a fuses, cables and a suitable sealant. The comprehensive installation instructions are simple to understand and supported with diagrams and photos.

Solar 4 RVs focus only on high quality products that are designed specifically for mobile and marine applications, ensuring they are lightweight, robust and efficient.

It is recommended that the batteries are placed at floor level above the axle(s) which avoids changing the tow ball weight and worsening pitching (front lifts or descends in relation to the back) and yawing (deviating temporarily from a straight course). Locating equipment at other locations is at the responsibility of the RV owner. Our product information includes the weight of each individual product.

The best method to ensure your system is functioning correcting is a battery monitor, it will show state of charge, current in/out, voltage, and time until discharge.

Some insurance companies allow small systems to be covered under the existing insurance policy. Your insurance company is best able to answer your questions. It is important that the products, the system design, the installation workmanship complies with all applicable regulations and standards. This is detailed in our installation instructions.

Solar Panel Questions:

A solar panel is a connected assembly of solar cells capable of producing a voltage when exposed to radiant energy (sunlight).

Photovoltaic (PV) panels are often referred to as just solar panels. Photovoltaic is a combination of the prefix 'photo', which means light, and the word 'voltaic', which means to produce a voltage or electric current. An installation of multiple PV panels is known as a PV array.

Sunlight on photovoltaic panel produces direct current (DC) electricity which is used to charge a battery.

There are several types of solar panel technologies, some of which are: monocrystalline, polycrystalline and thin film amorphous.

Monocrystalline photovoltaic (PV) solar panels are the most common, they have the best conversion efficiency (the conversion ratio is typically between 16 and 24% which means one square metre of panels exposed to full sun of 1000 Watt per square metre will generate 160W to 240W of electricity) which means they can get more out of each square meter of light than any other type of solar panel. Therefore, they are able to generate a significant amount of energy in a small amount of space.

There are many types of monocrystalline solar panels such as p-type, n-type, heterojunction transistor (HJT), passivated emitter rear cell (PERC) each with varying cost and performance.

Monocrystalline have a good power-to-size ratio, and an excellent lifespan. They experience a reduction in output at increasing temperatures. A reduction of between 12% and 15% can be expected on a very hot day.

Polycrystalline solar panels are similar to monocrystalline and are still widely used but the cells cost marginally less to produce, however as the cost of monocrystalline panels decreases, polycrystalline panels will eventually be made obsolete.

Amorphous Thin Film technology has optimal efficiency in hot weather and is less effective in cooler conditions. They perform well in partial shade but have a shorter lifespan and their conversion efficiency of sunlight to electricity is much less than polycrystalline or monocrystalline panels. Amorphous panels will require about twice as much space as other types of panels which limits their application on RVs because of the limited roof space. They are typically used in portable roll-up camping panels however they have a limited number of watts for the surface area (often 30 W and 60 W is offered).

This depends on how much sun shines onto your panels (Solar Irradiance) over time and how much electricity you use in your RV. The amount of battery storage you have will dictate how much energy you can store.

Solar Irradiance is the amount of solar energy that arrives at a specific area at a specific time. Solar irradiance varies depending on:

  • Time of day (elevation angle varies)
  • Season (elevation angle and strength varies)
  • Cloud cover, pollution (strength varies)
  • Shadowing

Solar insolation is a measure of solar irradiance on a given area over of period of time - typically over the period of a single day. Australian Government weather and climate agencies have this data across the Australian continent, and thus we can compare the average daily amount of solar energy that will "hit" the solar panels on our RV when it is in any part of Australia across an average year. Using this data we can predict how many solar panels you will need for Hobart in winter, or Darwin in summer, to meet your power needs.

The size of your solar system is defined in Watts (W) which indicates how big your solar system is (like a car engine size) not how much it will produce (speed). If you install a higher power system it will produce more electrical energy (a bigger car engine is more powerful). However, the amount of energy your solar cells produce is dependent on the amount, and intensity, of sun it receives (like fuel in a car). A car will go faster when you give it more fuel by pressing the accelerator. A solar panel will charge batteries faster if it receives direct sunlight for a long period. That is why we talk about Solar Irradiance.

The size of your solar system will usually be proportional to the amount of power you will use in your RV. We have designed a Solar Power Estimate Calculator (SPEC) that lets you work out how much electricity you would regularly use and what your ultimate power needs are.

Space and weight limitations and financial budget constraints may also limit or dictate the size of the solar system you choose.

Typically, a small RV with minimal electrical appliances may need as little as 100W, while a large RV with air conditioning may benefit from 1000W.

Plot the measurements of your roof space and mark out any obstacles.  Then using standard solar panel sizes see which panels will fit on the roof to maximise the power output.

Suitable Very High Bond (VHB) acrylic double-sided tape, structural silicone, bi-adhesive, eyelets are some methods able to be used. 

If a roof-mounted system proves impractical, then portable/blanket panels can be used.

Flexible solar panels are now designed to last over 25 years to match or exceed rigid solar panels.

Shade does reduce a panel’s efficiency but on a cloudy day there is usually still sufficient light providing energy to the panels. Under a light overcast sky, panels might produce about half as much as under full sun. Ideally the panels should receive no shading between the hours of 8am – 4pm. A bright sunny day that is cool or mild produces the greatest efficiency. On a really hot day the solar panels lose some efficiency, but summer is still the best time of year because of the stronger sunlight and longer daylight hours.

When the sun doesn’t shine on your solar panel (at night), it produces no power. The electricity that has flowed into your batteries while the sun was shining is stored so you can use that electricity at night.

Battery Questions:

Solar panels only produce electricity when the sun is shining. On cloudy days the output is less and at night there is none. Batteries store the power generated by the solar panels so you can use your appliances even when the solar panels are not producing electricity. Appliances are therefore being powered by the batteries not the solar panels. Batteries can be recharged by either the solar panels or mains power.

Lithium Iron Phosphate (LiFePO4), AGM, gel, OPzV, lead carbon all have good and bad properties. It is not as simple as thinking one is always better than another.

LiFePO4 have the highest energy density but are the most costly and do not perform in temperatures near zero.  Most LiFePO4 batteries house Battery Management Systems (BMS) internally.  The BMS will balance the cells to ensure a long lifespan and protect the battery from under/overvoltage by opening MOSFETS located inside the battery.  Approximately 20% of the cost of a lithium battery is the BMS, which is also the most likely and common point of failure.

AGM, gel and lead carbon are the cheapest but have the shortest lifespan.

OPzV have a long lifespan but are not practical for small applications.

An Amp-hour (Ah) describes a battery's capacity, or in other words, how long it will run before it is flat/drained/empty. The Amp-hour rating for a given battery is the maximum amperage that can be drawn continuously until the battery is completely discharged, flat, empty, drained, dead, over a specific time period.

Battery Capacity (Amp-hour) ÷ Solar Controller Output (Amps) = Charging Time (hours). Your battery will therefore take longer to charge with a smaller solar panel. Charging time will depend on the strength of sunlight, capacity of the battery and how much energy still remains in the battery.

Yes, the batteries can be charged by mains power, generator or from your vehicle. A mains chargers can be paralleled with other charging methods at the battery, so that you do not have to manually switch between chargers.

Over discharging a battery, for example by inadvertently leaving a light on, can result in permanent damage or failure of your battery.

To prevent this possibility, a low voltage load cut-off switch should be installed. This is a simple voltage sensing relay and is suitable for lead-acid batteries, including gel, AGM and lead carbon.

The new lithium-ion batteries have a very stable voltage during discharge, so it is generally not possible to determine the remaining battery capacity based on voltage alone. If a smart battery computer is installed, this can activate a load cut-off relay switch at a set remaining level of charge defined by the user (instead of low voltage). This type of load cut-off is also suitable for all types of lead-acid batteries including gel, AGM and lead carbon.

The number of batteries you require depends on how many electrical appliances you intend to use. Appliances draw electricity directly from the batteries, which are constantly being recharged by the solar panels through the solar charge controller. The number of solar panels you have, and how much sunlight they regularly receive determines how quickly your batteries are recharged.

We have designed a Solar Power Estimate Calculator (SPEC) that lets you work out how much electricity you will regularly use and what your ultimate power needs are. We then recommend a kit of the appropriate number and size of solar panels, batteries and other components. See our 'Assess your needs' page on the website.

Other Product Questions:

The solar charge controller charges the battery. In other words, it lets you store the energy being produced by the solar panels in the batteries so you can use the power when you need it. It also regulates the voltage and current from the solar panels and adjusts it to suit the batteries.

Each solar cell has a point at which the current (I) and voltage (V) output from the cell result in the maximum power output of the cell. A PV panel has a maximum efficiency at only one point in the V vs I load curve. An MPPT solar controller automatically and constantly tracks the maximum power point of the PV Panel and ensures that you get the most power possible from your solar panels at any point in time.

It is particularly effective during low light level conditions. During low light level situations, it will compensate for the low light level and find the new point at which the solar cell delivers its maximum power output. Note that the MPPT of the panel moves with solar intensity, temperature and aging of the panel.

The battery computer display shows the remaining level of charge of the battery like a “fuel gauge for the battery”.

The battery computer constantly measures the battery voltage together with the current into and out of the battery. It must also have knowledge of the battery capacity - it "learns" this after installation when the user puts the battery through a full charge and discharge cycle. Thereafter, by monitoring of the charging and discharging current, together with programmed characteristics of the battery type, the precise level of charge of the battery will be constantly calculated and shown on the display in remaining charge (%) or in remaining Amp-hours (Ah). It also shows the battery voltage and charging or discharging current.

An inverter converts 12V DC from your battery into 240V AC. If you only need 12V power then you do not need an inverter. Portable inverters provide 240V at the inverter itself, while the output of suitable inverters can be permanently wired by a licensed electrician into the 240V circuit of your caravan / RV.

Australian Standard AS-4763, "Safety of portable inverters" defines three types of portable inverter, of which two types may be permanently installed and connected to the electrical circuits in you caravan or RV.

A portable inverter complying with Australian Standard AS-4763, "Safety of portable inverters" with a socket outlet can be used in a caravan. In this case the user simply plugs an appliance directly into the socket outlet of the inverter. No installation takes place in this case, so an electrician is not required.

In regard to the permanent connection of inverters into a caravan / RV, Australian Standard AS-3001, "Electrical installations-Transportable structures and vehicles including their site supplies", requires that inverters placed into RVs and caravans must comply with Australian Standard AS-4763, "Safety of portable inverters" and be of the isolated or RCD protected type. AS-3001 makes no provision for the installation of any other type of inverter.

Where the AS-4763 compliant inverter is of the isolated type, AS-3001 permits the inverter to have a socket outlet into which the electrician makes the connection to the caravan mains circuit.

Where the AS-4763 compliant inverter is of the RCD protected type, AS-3001 requires that the inverter is permanently connected, i.e not via a socket outlet.

The permanent connection of an inverter into a fixed electrical circuit in a caravan must be carried out by an electrician in accordance with AS-3001. The caravan mains circuits shall include circuit breakers and RCDs and be wired in accordance with AS-3001.

The information provided here is a summary written in layman terms. Australian Standards and State Laws must always be complied with

Non-true sine wave (often called modified sine wave) inverters are generally smaller, lower cost, lower power devices and are suitable for most equipment. However, even if equipment can tolerate the modified wave-shape it will often will not operate as efficiently with excess heat being produced; AC motors particularly may overheat. Non-suitable devices may not work properly or be permanently damaged.

Pure sine wave inverters produce a similar quality wave shape as provided from the grid into your home, and thus guarantees that all equipment will work just the same as in your home.

Only pure sinewave inverters compliant with AS-3001 and AS-4763 should be permanently connected into the fixed mains circuits in an RV. This agrees with AS-4509 Stand-alone power systems Part 2: System design, which requires that inverter selection considers the harmonic content of the waveform. Modified sine wave inverters have a high harmonic content dependent on their design, whereas true sine wave inverters have a total harmonic distortion (THD) of generally better 3%. A user would reasonably expect that when an appliance is plugged into a socket outlet in the caravan it will work properly and not be damaged. Therefore, using a pure sinewave inverter eliminates the possibility of (expensive) damage to an appliance or device when plugged in by current owners, guests, future owners, or service people.

Note: grid-feed inverters (not used in RVs) have a separate specific requirement for the quality of the waveform (harmonic content).

The information provided here is a summary written in layman terms. Australian Standards and State Laws must always be complied with

Several different types of cable are used, each for a different purpose.

Solar Cable: The cable from the PV Panels to the solar controller is the same standard as that required by Australian Standard AS-5033 for use in residential installations, namely PV1-F which is tested and approved to TUV standard 2 Pfg 1169/08.2007.

12V Cable: Automotive grade cable to AS-3191 with insulation to V90 or V90HT grade. The appropriate size cable is provided to minimise cable voltage losses, but at the same time avoid adding unnecessary weight.

Mains Cable: Mains cables in transportable vehicles must comply with AS-3001 which requires that conductor cross-sectional area is not less than 1 mm2 and not less than seven strands consisting of either - (a) multi-strand insulated and sheathed cables; or (b) flexible cords. In practice, flexible cord is preferable as this is best able to handle the stresses induced into the cable due to vibration and movement. The flexible cable often installed into caravans is a 2.5mm 3-core thermoplastic PVC, V-90 sheathed cable to AS-3191, Electric Flexible Cords.

The information provided here is a summary written in layman terms. Australian Standards and State Laws must always be complied with.

Installation Questions:

Installation is generally straightforward, although knowing where to locate the equipment can sometimes be a challenge due to space limitations. As we provide the necessary cable for the installation, the location of all equipment items and cable runs need to be determined before placing an order for a kit.

Prior to the commencement of installation, to ensure personal safety and the safety of the equipment, the detailed installation instructions must be read through in their entirety.

The ideal location for the batteries is over the axle(s) as this will not change the tow ball weight and provides the best towing dynamics. However, there is often little or no space adjacent space over the axle for the solar controller and inverter, noting that the mounting orientation of the solar controller and inverter, together with venting requirements must be observed.

The space behind the fridge is often the best place to run the cables from the roof to the solar controller. The cable distance between the solar controller and the battery should be kept to a maximum 2m; as the cable length increases the efficiency of the battery charging will reduce. The distance between the battery and inverter should also be minimised, less than 1 metre is ideal. Again, increasing distance leads to losses in the cable and thereby reducing the real useable capacity of battery.

Assuming that suitable locations have been established for all items and cable runs, the actual installation is straightforward. Care needs to be observed if equipment is installed behind external grills because washing the RV with a hose could lead to water being sprayed into equipment.

The solar panels are attached to the roof of your RV with a suitable very high bond acrylic double-sided tape, structural silicone or securing through eyelets. The cables are run via a roof cable gland box so that the cables enter the RV at a convenient location. Until the panels are wired to the solar controller the solar panels should covered to avoid any voltage appearing at the end of the cables.

Installation (i.e. mounting and connecting up sequence) and commissioning (i.e. powering up and testing) inside the RV follows a logical order of installing each item of equipment and connecting the cables, but leaving the fuses removed until the commissioning phase. Installation of equipment connected to mains voltages, cables, isolation and protective devices must be installed and commissioned by a licensed electrician if 240V.

The commissioning sequence and intermediate checks are detailed in the sequence is, however a summary of the sequence is:

  1. Connect the solar controller to the battery and check solar controller status
  2. Connect the solar controller to the solar panels – then remove the cover from the panels. And check the solar controller status and the battery monitor.
  3. Connect the battery to the load (power consumers) and check operation.

Connect the inverter to the batteries. Check inverter status, battery status, mains status and operation of the system running various loads

You do not need an electrician to install a 12V kit. For a 240V non-portable kit you will need an electrician if the inverter outlet is connected to fixed wiring in the caravan / RV.

To explain this further: Section 45 of the Electricity Safety Act 1998 states only certified persons and organisations can undertake “Prescribed Electrical Installation Work”. Certified organisations and professionals must themselves comply with the Australian Standards. On the internet, there are many instances of incorrect interpretations of parts of the Australian Standards. State laws may place additional requirements to those in the standards.

What this means is that an electrician is required to install an inverter that is connected into the a mains circuit as this is covered under “Prescribed Electrical Installation Work”. In the context of RVs, “Prescribed Electrical Installation Work” covers equipment, isolation and protective devices connected to mains voltages, other than consumer appliances connected via socket outlets. Note that although the solar panel, 12/24V equipment and cabling need not be installed by a qualified tradesperson, there are still some requirements in the Australian Standards to be observed. For example, The Wiring Rules, AS3000, requires that 12/24V (which is within the range of Extra-Low-Voltage defined in AS3000) and mains voltages (defined as Low Voltage in AS3000) must be separated. The standard defines several methods by which this can be achieved, all of which requires physical insulation barriers. With the automotive cable used for the 12/24V, the only method that is feasible is to run the mains cable in a conduit in all compartments or cable runs where automotive and mains rated cable are present. A misconception on one web-site states that a 50mm separation is all that is required, however this requirement relates to minimising electromagnetic coupling between mains cabling and communication cabling.

In accordance with AS3000, the electrician is required to conduct insulation resistance tests between the mains and 12/24V system to verify isolation between the two systems. Hence if the RV owner installs the 12/24V equipment and cabling, this must be done prior to the electrician installing the inverter and mains cabling and protective devices.

The information provided here is a summary written in layman terms. Australian Standards and State Laws must always be complied with.

Maintenance Questions:

Solar PV panels have no moving parts and require no maintenance other than the occasional cleaning as needed. A build-up of dust, sap from trees and bat or bird droppings will decrease power output so if the panels require a clean this can be done with a low pressure spray from a garden hose and brush/broom or sponge. High pressure jet should be held sufficiently far away so that the pressure on the surface is no more than the low pressure spray from a garden hose.

The inverter and solar controller should be checked periodically to ensure that venting is kept clear.

Under the Australian Consumer Law (ACL) a consumer has specific rights in regard to the purchases and services they acquire. These are automatically granted and do not have to be purchased. The ACL guarantees that all goods:

  • are of acceptable quality;
  • match the description, sample or demonstration model;
  • are fit for their disclosed purpose;
  • will have spare parts and repairs available for a reasonable amount of time after purchase unless stated otherwise.

Depending on whether it is a major or minor failure, ACL states a consumer may be entitled to a repair, replacement, refund or compensation