I’ve often sat outside my van or motorhome, soaking up the sun, wondering how many solar panels do you need on the roof. The panels I have seem to work great, but I wonder if there is an optimal amount of solar panels to put on your RV, motorhome or van. I decided to do a bit of digging on the internet to answer the question of how many solar panels do you need on your roof.
Benefits of Solar Panels
Having solar panels on your motorhome, van or RV is a game changer. Instead of relying on the vehicles alternator to charge your house battery, you get free energy from the sun. There’s no need to be driving, using expensive petrol or diesel for your batteries to charge. You can park up by the lake, river, beach or the middle of nowhere, and as long as you have daylight your batteries will charge.
Generally speaking, solar power is easier and safer to install than AC mains supply. You can get your solar system professionally installed or you can do it yourself. An AC mains supply where you hook up to camp ground power should be done by a professional and must be signed off by a professional before it is legal.
There’s no moving parts or mechanics to maintain with solar panels. Compared to a generator or wind turbine solar panels are efficient, virtually maintenance free, and silent. So, how many solar panels do you need?
How Many Solar Panels Do You Need? Two Schools of Thought
There are at least two schools of thought on the question of how many solar panels do you need to have. Some people will give you a definitive answer, and others will say it depends.
There are formulas you can use to work out how much power each appliance you intend to use consumes, and from there you work out how many hours a day you’ll use them, which gives you an estimate of your daily power usage and therefore how much output you need from your solar panels. You can even find nifty calculators online that you can input the numbers and it will provide an answer.
The other school of thought is that you can never have enough solar panels, or at least – the more the better and get what you can afford.
I’d pick a mix of these two, I’m probably in the middle although leaning towards the, “you can never have too much solar”.
You can input numbers and come up with a figure on paper, but do you really know every appliance you intend to use and for how long each day? What if you only want to charge a laptop computer initially, but later on find you need to run two laptops plugged into good sized monitors all day? Possibly a bit far fetched but not unheard of.
Solar is very dependent on the weather and season. What if you get two or three weeks of bad weather that limits your daily charging? When working out your numbers by the first method all this needs to be factored in. In winter there are less daylight hours and the sun is lower which equates to less charging.
I have 1100 watts of solar panels on my motorhome which is approximately two thirds of the roof space covered. As one person put it, no one ever regretted having too much solar but many have regretted having large battery capacity and not enough solar. In reality, numbers on paper can be very different to motorhoming in real life.
My van has one 270 watt panel. Given I don’t use as much electricity in the van my 270watt panel is adequate. Click here to read about my solar and electrical set up in my motorhome and van.
The Different Types of Solar Panels
There are three main types of solar panels that you’ll hear about. Monocrystalline, polycrystalline and thin-film solar panels.
Monocrystalline panels are the oldest type of panel and also the most developed technologically. They’re made from a single (mono) crystal silicon solar cells. They’re considered to be a premium panel with a high efficiency and output. They’re recognizable by their black, uniform appearance.
Polycrystalline panels are less efficient although often more affordable. The polycrystalline cells are also made from silicon but in contrast to the monocrystalline panels, these are made from many (poly) fragments of silicon crystal melted together. These panels appear bluish in colour and speckled as the light reflects of the many crystal fragments.
Thin-film solar panels are thin and flexible. They’re made from layers of semiconducting materials such as silicon, copper indium gallium selenide and cadium telluride. These panels tend to have a lower efficiency compared to crystalline panels.
Best Type of Solar Panel
You’ll likely be choosing between monocrystalline and polycrystalline panels. The best type will depend on your circumstances. How much roof space do you have and what can you afford? Polycrystalline panels are somewhat cheaper but less efficient, you might need more of them, whereas if your roof space is limited you might choose to pay a bit more for monocrystalline panels which will be more efficient but less of them needed. How many solar panels do you need for your installation? It’ll likely be dependent on the type of panel you install.
Fixed Solar Panels or Portable?
During my travels I’ve seen motorhomers with portable solar panels. This can be an option to supplement your panels on the roof or an option if for some reason you don’t want to mount panels to your roof. Keep in mind however, that a portable panel is probably not going to provide enough energy output for a normal to moderate user of power. It may be fine if you just want to charge a phone, laptop, run your lights at night and a few other small items, but you’d need to watch your usage.
A portable panel would be ideal to supplement your existing panels on the roof. Panels flat on your roof don’t put out as much power as a panel aimed directly at the sun. In winter, being able to point your panel at the sun can make a huge difference to the panels output. Therefore in winter time a portable panel would be ideal to supplement what you have on the roof.
In the summer time you may want to park your vehicle in the shade during the hottest parts of the day. Having a portable panel with a long lead means you can still get charging for your batteries if you can place the panel in the sun while your vehicle is in the shade.
How Many Solar Panels Do You Need for Cloudy Days?
Your solar panel will work on most cloudy days. A very cloudy day with really thick dark clouds may mean that it won’t work at all though. But on most cloudy days you’ll be able to get solar output although it will be a lot less than on a sunny day. This is the reason you want to have as many solar panels as you can. So how many solar panels do you need to get you through cloudy weather? On a cloudy day one solar panel might put out 1amp. If you have two you now get 2 amps. Four panels equals 4 amps. There are other factors at play, but in short this is the principle idea behind having plenty of solar. On those cloudy days you’ll have enough to get by.
Solar Panel Maintenance
To get the most from your solar panels you should ensure they’re clean. Even a small amount of debris, dead leaves or dirt on your panel can reduce it’s output dramatically. A mild detergent in water is safe to use on your panels. During cleaning you can also inspect any connections that you can see to ensure they’re secure and free from damage.
What Components Do You Need for a Solar Power Set Up?
Your solar panels are connected by cable to a solar charge controller. This in turn is connected to your battery. Your battery gives you power, either as 12 volt, 24 volt or even 48 volt depending on your system. Most motorhome, van or RV set ups will be 12 volt. You may also have an inverter which can provide you with mains power.
The charge controller is an important part of your solar power system. There are two types of controller. PWM and MPPT. For more about solar charge controllers read our thoughts here.
Your battery is connected to the charge controller. There are many types of battery available including lead acid, GEL, AGM, Carbon, and Lithium. Check out our guide about batteries for your motorhome, van or RV here.
Check out our tips for van life traveling here.