A Guide To Solar Panels For Caravans and Motorhomes

A Guide To Solar Panels For Caravans and Motorhomes

Posted on June 27, 2014 by

Caravan with free standing solar panels

 

One of the major advantages of caravans and motorhomes is the freedom they give you to really get away from it all. Well, as far away from it all as you can get while still needing access to a pitch with electric hook-up, that is. What do you do if you want to go somewhere really remote and peaceful? Or if you don’t want the additional expense of an electric hook-up? Easy – you invest in some solar panels.

Ok, they won’t be cheap to start off with but just think of the opportunities. With some solar panels providing your electricity and hot water, you can go absolutely anywhere. And yes, they do work perfectly well in the less-than-tropical British sun! Although solar panels do involve some financial outlay, the savings they enable you to make mean this is well worthwhile.

More freedom, cheaper pitches, considerable cheaper power and instantly boosted eco-credentials – what’s not to like about solar panels?

If you’re considering making the switch, or are just interested in learning a bit more about this greener power source, you’ve come to the right place. Read on for our comprehensive guide to solar panels for caravans and motorhomes.

Types of solar panel

There are currently two main types of solar panel available – thin film and crystalline. Both are officially known as photovoltaic, or PV, panels.

  • Thin film PV panels are produced by spraying a thin layer of semiconductor material onto another surface (similar to the silvering on the back of a mirror). Typically, a thin film solar panel will last around ten years, which is less than the average crystalline panel. However, technological advances mean they are constantly improving and may soon be able to match the twenty-year lifespan of crystalline panels. Thin film panels are generally the significantly cheaper option.
  • Crystalline panels come in two types – mono-crystalline and poly-crystalline. Mono-crystalline panels are the most effective out of all types of solar panel, with each module formed from a single silicon crystal. However, while they are the most efficient solar panels, they are also the most expensive. Most of the crystalline panels you will come across will be mono-crystalline and made from a large number of small crystals. The difference in efficiency means that you will need a larger poly-crystalline panel to generate the amount of energy you need. It is worth bearing in mind that the difference is quite negligible when it comes to powering a caravan or motorhome, but may be an issue if you intend installing panels at home too.

You will also need to choose between free-standing and roof-mounted solar panels, each of which come with their own advantages and drawbacks (a lot of which depends on personal preference).

In general, free-standing solar panels make it easier to generate as much power as possible by positioning the panel to catch as much sun as it can. However, they can be cumbersome and difficult to store and transport when not in use, not to mention the fact you need to leave them unattended from time to time. A number of users also complain that these panels tend to attract flies and insects, which obscure the sun and somewhat defeat the purpose of being able to angle it!

Roof-mounted solar panels are permanently fixed to the caravan or motorhome, meaning they can’t be as easily angled to catch the sun. The major advantages of these are that they don’t take up storage space or need to be transported separately and there is no risk involved in leaving them to do their thing during the day.

As always, you will get what you pay for, so try to stay away from buying the cheapest option available. The most efficient model will rarely be the cheapest! Of course, this doesn’t mean you should be sceptical about all amazingly-priced solar panels – just remember to keep an open mind and research thoroughly.

How to choose the right solar panel

It’s important to spend a decent amount of time researching solar panels before making a purchase, as buying the wrong one for your caravan or motorhome is likely to be wasted money and enough to put you off solar energy for quite some time. If you choose one with too low an output, you’ll end up running out of power regularly and getting fed up; going for one which is too big and powerful means you’ll have spent more than you needed to and don’t really get value for money.

Before you buy a solar panel, take your caravan away for a short break and measure how much electricity you use. Set off with a fully-charged battery, stay away from the electric hook-ups and see how long the battery lasts for. Don’t overuse your appliances deliberately to use as much power as possible; use your caravan as normal to get a true picture of how much electricity you actually need. Do this over a few days as one day is unlikely to provide an accurate result.

Once you get home, use your battery’s rating to calculate your average energy use. For the purposes of calculating and converting battery power to solar panel requirements, the quick guide below should come in handy:

Power (watts) = current (amps) x voltage (v)

Energy (watt hours) = power (watts) x time (hours)

Battery capacity (amp hours) = energy (watt hours)/voltage (volts)

As an example, if you have an 110aH (amp hours) battery and it has lasted for two days on your trip, you need an average of 55aH per day.  Therefore, you will need to choose a solar panel which can provide 55aH of power per day. Bear in mind that your solar panel will only be able to recharge your battery during the daylight hours.

If you can’t get away on a short break to calculate your energy use, there is another way of doing it (albeit a less fun and more complex method).

Calculating your energy use manually requires the power ratings of every piece of electrical equipment or appliance you intend to use. As a battery uses around 12 volts to power electrical equipment, the power rating should be divided by 12 to work out how much that particular item will drain from the battery.

For example, a 16 watt light will require 1.33 amps per hour of usage. If you normally use that light for three hours per day, you will need 1.33amps x 3 hours = 4aH per day just for that particular light.

Repeat this calculation for each piece of electrical equipment and add all the results to find out how much power you will need your solar panel to generate. With regards to how much power your solar panel will be able to generate, you can normally expect around 6 or 7 hours of recharging time on a solar panel pointing towards the sun on a typical UK summer’s day. However, during the winter, this could drop to just 0.8 hours.

It is recommended that you include devices with built in solar power in your calculations too (such as solar-powered mobile phone chargers), as they will also require battery power during periods of little sunlight.

Now that you know how much power you need, use this table to work out which panel will do the job:

Solar Panel Rating

4W

10W

20W

25W

25W

80W

100W

150W

Summer Power Generation (per day)

24-28Wh

60-70Wh

120-140Wh

150-175Wh

300-350Wh

480-560Wh

600-700Wh

900-1050Wh

Winter Power Generation (per day)

3.2Wh

8Wh

16Wh

20Wh

40Wh

64Wh

80Wh

120Wh

Please note that the figures given in the table are intended as a guide only; the weather conditions at any given time will affect the amount of power which is actually produced.

This calculator may also come in handy. It has been designed for the US so, for the purposes of UK caravans and motorhomes, the wattage will remain the same but the current should be halved. This ready reckoner is also very useful (and aimed at the UK market).

 

Motorhome with solar panels on the roof

 

Regulators and charge controllers

If you intend to install a large solar panel, it is sensible to consider fitting a regulator too, to prevent your battery from being damaged through over-charging. To calculate whether or not you will need a regulator, divide the rating (Ah) of your battery by ten. If the power of your solar panel is less than this figure, you should be ok without a regulator. Otherwise, it is highly recommended to have one fitted to the circuit.

A charge controller will normally include a regulator and a diode which prevents energy from seeping back into the solar panel from the battery when it is dark. Check what the controller includes before buying, as not all manufacturers will use the same definition and naming convention.

It can also be a good idea to use an inverter to prevent you from running your battery down completely.  Some inverters that are available on the market will prevent you from totally discharging your battery and may have an alarm to warn you when it reaches a certain level.

Caravan and motorhome solar panel top tips

  • When using a crystalline solar panel, remember that even the tiniest shadow can affect the amount of power generated. Always ensure as many cells as possible are in direct sunlight.
  • Glass or plastic will dramatically reduce the amount of power produced by a solar panel, meaning it could take up to three times as much sunlight to recharge your battery. Again, you should always make sure as much of the panel as possible is in direct sunlight.
  • Before buying a new solar panel, check with your caravan or motorhome’s manufacturer that it will fit to your van easily. You may need to purchase special adapters if the standard clips will not be sufficient.
  • Position your solar panel to catch as much of the midday (strongest) sunlight as possible. This is normally directly overhead during the summer, but you will need to re-position the panels at other times of year.
  • Remember that your battery needs to be kept in excellent condition to be able to produce enough energy. Maintain and replace the battery as needed to ensure optimal performance.
  • If your caravan or motorhome is under warranty, be aware that fitting a solar panel may invalidate it, unless the work is carried out by the manufacturer’s own tradesmen
  • Although not much energy will be generated during the winter months, a solar panel of at least 20w should be enough to keep your stored caravan ticking over until you next need to use it
  • Replacing inefficient halogen bulbs with LEDs can make a huge difference to the amount of power you use and, therefore, the amount you need your solar panel to generate
  • Remember that pollution, dirt, traffic dust and bird droppings can prevent sunlight from reaching your solar panel. Clean your solar panels regularly with warm water and dishwashing soap to remove grime and keep your panels as efficient as possible. If you notice a drop in the amount of power produced, cleaning the panels is one of the most common and most easily rectified problems.

Where to buy solar panels

There are plenty of solar panel suppliers in the UK, with some of the most popular including the following:

This list has been provided to help make your research easier and is not a recommendation or endorsement of any products.

Whichever you decide to buy, make sure that you tell your insurance company so that they can be included within either your caravan or motorhome policy. If you would like a quote or advice on your insurance, call us on 01480 402460. We think you’ll be pleasantly surprised at the level of cover we offer and our low prices.

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Comments

Terry Walker 2nd August 2014

I have been using a “briefcase type” 13 watt double solar panel for about 14 years with excellent results. It is a Topray model and was on offer at £50 instead of £100.I never use hook-ups as I always go on remote fishing sites. Although I use TV in the evenings, this proves sufficient for topping up my 110Amp hour battery. An excellent buy.

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Chez 2nd August 2014

Hello and thank youfor an informative breakdown on using solar panels.

sadly I have two comments to make,
firstly, you say “Power (watts) = current (amps) + voltage (v)”, when in fact this should actually be Watts = Amps X (times) Volts
your equation would give a 5 amp load a power rating of 17 watts, when in actual fact it would be 60 watts

secondly, you later mention to use an inverter “to prevent your battery from running down completely”
An electrical inverter by definition will convert one voltage level to another but in the camping sense will step up the battery 12v DC upto 240v AC which is what we associate with mains electricity.
(Its transformers that act the other way around and transform, or step down one voltage to a lower one, although generally transformers are only used for alternating currents).

I have to question how your suggested use of an inverter would prevent the battery from running down? After all to use an inverter you would have to connect it to the battery and that would only allow you to use mains rated equipment, but the downside to this is that inverters do not work free of charge and there is always a power loss when in use, sometimes upto 50% depending on model, meaning half the battery power being consumed, is therefore wasted in the conversion, with the result that your battery would actually run down faster than if you could have used similar, but 12v rated products instead.

the only advantage to using an inverter would be because of its ability to shut down automatically should the battery voltage fall to a critical level whereby if it was crossed, could cause possible permanent damage to your battery

Thanks for a great article, but I hope you appreicate my comments too 🙂
Kind regards,
Chez

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    Sandra Hamilton 5th August 2014

    Hi Chez,

    Thank you for taking the time to comment and correct me – it is appreciated. I am always happy to correct mistakes or explain myself better.

    What I meant about the inverter was that they can be useful as some of them will protect you from discharging your battery totally – some apparently can sound an alarm when the battery power is getting low.

    I’ve updated the article accordingly.

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Al 2nd August 2014

Excellent article. Dropped into my inbox just as I was thinking about our next trip away and how we would cope without mains hook-up! Visited each of the websites mentioned and compared all the suitable kits and found one from Sunstore that met all my criteria!

Many Thanks.

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J Montgomery 9th August 2014

Another advantage worth considering is that fitted solar panels will keep your batteries always fully charged. I have a Hymer motorhome with 2 panels fitted-I never have to charge my batteries and am always ready to go.

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jim beveridge 14th August 2014

I use 40 watt suitcase, totally satisfied put it up through sky light safe and secure.

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Dave Minikin 17th August 2014

I have just fitted a 100 w solar panel to my caravan. If I want to use a hook up do I need to disconnect the panel. There is a regulator fitted

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    Sandra Hamilton 18th August 2014

    Hi Dave,

    Thank you for your question.

    As far as I can ascertain, you should only use one source of power at one time and therefore the panels should either be isolated at the on / off switch or disconnected if you intend to use electric hook up.

    If you are unsure in any way then I would recommend that you talk to company that supplied / installed your panels as they will be far more knowledgeable than me.

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Arthur Branthwaite 20th August 2014

I have recently fitted had a100 w solar panel by a guy who advertises in Caravan Club magazine . He is based in Derby and came up to Cheshire to fit it for me. Job done including controller for a very reasonable price
I went away for two weeks and delighted with the results, and incidentally to answer Dave Minkin’s query, I was told there is no need to disconnect the panel if you use hook up. Excellent piece of kit and well worth having and a cost saving in the long run!

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A.Branthwaite 21st August 2014

Hi Dave
I had a 100w panel fitted recently and was told that it was not
Necessary to isolate the panel when using hook up.
If you have the advised controller fitted you don’t even have to have your main switch on in the van, just let it do it’s job in the sunshine !

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Robert Courts 6th September 2015

I have a 150 watt solar panel and it is split to two 110ah battery’s and the engine battery, i am wondering what i should be switched onto while driving and also when parked up. Pity we cannot add a photograph here,

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    Sandra Hamilton 8th September 2015

    Hi Robert,

    Thank you for your question.

    I am by no means a technical expert and I would therefore suggest that you have a chat with either your local dealership or the seller / manufacturer of your solar panel. I would hate to give you incorrect or even damaging advice.

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Frank Damm 9th October 2015

I would like to buy a full package of Solar Panels/Battery etc for a remote summerhouse. I plan to run lighting, small fridge, Radio/CD player. What rating would I need and could you suggest a suitable package for me and supplier information.
Thank you.

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    Sandra Hamilton 12th October 2015

    Hi Frank,

    Thank you for your question.

    Firstly, it depends on what type of lighting you are going to install as some types are far more energy efficient than others, but may emit a ‘dimmer’ light.

    Again, the same applies to the fridge as a caravan fridge will run on less electricity than a standard domestic fridge.

    To be honest, before you buy any equipment for your summerhouse, I would work out how much power each item is going to use and then go and speak to an expert. The solar panel industry is constantly changing and improving and I wouldn’t want to give you any false information.

    Depending on how remote your summerhouse is, it may be cheaper to bury an electric cable, or even use a generator.

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      Warwick Nixon 11th October 2016

      I would advise that a “normal” caravan fridge will need 8 to 10 Amps on 12V DC, and would require ‘serious’ solar panel output to keep up with it!
      At night time, will flatten a leisure battery quickly.
      On 240V AC, a caravan fridge uses markedly less power than a “domestic” type.

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Billy Thomson 12th February 2017

Confused, I was told that solar panels only need light not sunshine?

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    Sandra Hamilton 12th February 2017

    Hi Billy,

    Thank you for your question.

    Solar panels will take some power from daylight, but for the best results and a better / quicker charge, direct sunlight is best.

    A good basic comparison are the solar lights that some people have in their gardens. In the winter when there is very little sun, the lights will charge only a small amount and may not even work when it gets to dusk. In the summer, the lights will get a full charge quickly and I’ve seen some that are still lit just before dawn the following day.

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Dave 26th August 2017

Hello , iv bought a burger van and I’m looking for solar panels to help keep the fridges running in it over night , any suggestions please ?? They are normal household fridges

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Miss Piggy the Citroen HY 21st September 2017

Hi. I have two solar panels of 120 watts each fitted to my campervan and these charge my two 110 Ahr batteries and my engine battery very effectively. I bought the whole kit from sunworks.co.uk a few years ago. They were exceptionally helpful and I recommend you talk to them about your proposed system.

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