How many watts should a solar system on a mobile home have? A question that comes up again and again. There is no general answer simply because too many factors come into play. And my solar calculator goes into this: it takes the power consumption in the mobile home and the voltage (12V / 24V) as the basis for calculating the solar system and battery for your (future self-sufficient) mobile home.
Solar calculator for 12V / 24V
One important piece of information to calculate a solar system’s reasonable size is the daily power consumption in watt-hours (Wh). Because this is where most travellers fail, there is a solar calculator here in which the basic consumers are already entered: Consumers that are standard in most mobile homes: refrigerator and heating on gas, light by LED, otherwise some television, water pump, and internet. However, electricity consumers that go beyond the standard can also be entered here: fan heaters, air conditioning, compressor refrigerators, or induction hotplates quickly boost the result in the solar calculator.
How many watts should my solar system bring for the mobile home?
Some get by with 100W or 200W; our solar system is a bit larger with 1600W – but given our power consumption, it is not oversized. We also have a solar bag with us for emergencies. And know what tricks we can use to reduce our electricity consumption.
However, an off grid solar system makes no sense for every mobile home. Daily driving from one campsite to the next, mainly weekend trips? Or even north in winter? Charging the battery in the mobile home using shore power and the alternator (depending on the vehicle with a cut-off relay or charging booster) can be a more sensible alternative. A solar system makes sense when more independence is desired.
- It’s about not having to keep driving just because the power is gone.
- And about saving the $4 electricity fee a day at the campsite.
- It’s about choosing where to stay for the beauty of it – not whether there’s an outlet.
Above all, it’s about making the promise of freedom in mobile home commercials a reality.
Calculate the solar system for the mobile home – the basics in the solar calculator
The size of the solar system
should be designed in such a way that it covers the daily consumption in halfway sunny weather. So if you have determined a power consumption of 1,000Wh, then according to my calculation, you should be fine with a 200W solar system – in summer, when the sun is shining. We also have a complete solar system camper set in our range – more precisely, several. The solar set ECO with 100W monocrystalline solar panels or the solar set MAXI with 220Wp solar panels would be suitable. If you plan to spend the winter in Portugal with your motorhome, you won’t get very far with it. Then it says another 300W on the roof or a larger solar bag. Unless, of course, you spend the winter on a campsite with a flat electricity rate. Then it’s worth doing the math yourself: 3$/day for electricity x 100 days = 300$ electricity costs in one winter.
The capacity of the battery
It should be large enough so that the lead battery (GEL or AGM) is normally not discharged more than 50%. The deeper it is discharged, the fewer cycles it makes, so the more likely it is to fail. The lead battery prefers to be full. The 12v lithium battery as a mobile home battery is a little different: they prefer to be almost full and are more forgiving of a complete discharge. In other words: it is much more difficult to scrap a lithium battery.
Calculating the size of the solar system: soft factors
The solar power calculator indicates how many watts a solar system should have on the mobile home or caravan. However, other factors should be considered when calculating the required total output of the solar modules and the battery capacity.
How else are the batteries charged?
Solar is a way to charge your RV batteries in the camper. Mobile homes have an additional feature built-in: charging via the alternator. Here the starter battery is usually connected to the supply battery. And, of course, you can plug your motorhome into the socket: at home, on the campsite, or at the motorhome site.
Shore power and alternator
An electroblock (EBL = ElektroBLock) is installed in mobile homes. A combination device consists of a cut-off relay (charging via the alternator while driving) and a 230V battery charger (charging via 230V shore power). If you regularly have the opportunity to charge your battery here, you can expect a lower output from the solar system. But you can also think about investing more money in a solar system as we do: With up to $3 a day for electricity at the campsite and additional diesel consumption when driving, it can pay off – at least for frequent travellers.
Power generator
A small power generator for power emergencies is carried in the rear garage. Right down to the gas unit, permanently installed under the mobile home so that the air conditioning can run from 22 degrees: there are different starting points here. Here you should be aware that neighbours could be disturbed by the noise from the generator – this could also apply to you. A generator is only used if the weather has been insufficient for the past few days or if the calculations for the solar system have not been sufficient.
Folding module
As a replacement or extension of the mobile home solar system, a foldable solar module – also known as a solar bag, is particularly popular with winterers in southern Europe. Because especially when the sun is low in the sky. The foldable solar module can catch twice as many herrings as a solar system with the same rated output installed flat on the roof.
The folding module is also often used in small vehicles, where it is impossible to pack a solar system with decent performance on the roof. Overwinterers in the south like to use it to expand their solar system designed for the summer.
Shadow parker
Shade the mobile home in the summer? Not good for the solar yield at all. Campsites with many trees also ensure (partial) shading of solar modules. Parking between houses in the city or the shade of a mountain – if you don’t always stand in the blazing sun, you should calculate the wattage of your motorhome solar system so that it is sufficient even in the shade. This also applies to holidaymakers in Germany: clouds also create shadows.
Destinations: how high is the sun, and how hot is it?
In winter, the days are shorter than in summer, and the sun is lower in the sky. The low point of the sun (winter solstice) is around December 21st. From then on, the days get longer, affecting the solar yield. The further north you go, the shorter the winter days become. So if you want to go to Scandinavia to see the northern lights, you have a bad hand – the solar system will hardly provide electricity. In Andalusia, on the other hand, with appropriately generously dimensioned photovoltaics, it is easily possible to spend the winter without electricity – with a bit of luck with the weather.
In summer, the temperature plays a role: the hotter it is, the lower the solar system’s efficiency. Therefore, the best yields can often be measured in spring or autumn.
- Winter in southern Europe: lots of suns, but the low position of the sun
- Summer in Central Europe: the medium amount of sun
- Summer in southern Europe: lots of sun, but high temperatures
- A lot helps a lot: medical reasons for a large solar system
Travellers with (chronic) illness should pay particular attention to the reliable functioning of the power supply in the mobile home – and possibly also consider this when calculating the solar system. Heat-sensitive medicines stored in the cool box should be kept cool throughout. The apnea device should not fail at three o’clock in the morning. And if you need an electrically powered base to be mobile on-site, you should also ensure that there is always enough electricity in the mobile home.
Solar system for mobile homes: solar panels, solar controllers, inverters, batteries.
Such a solar calculator is all good, but until now, it only says what the output of a solar power system should be and what the capacity of the batteries is. Important cornerstones, but not all components of a functioning power supply in the mobile home. Especially when converting a mobile home, you are quickly confronted with the fact that something has to be “somehow” between the solar module, the mobile home battery, and the current stretcher.