Your System









Offgrid Solar Configurator

We need to estimate how much sunshine you can expect to dimension the solar panel size.

Where will you stay?

The numbers represent the hours of sunshine – min and max sunshine per month aswell as the total yearly average.

Select the months of your travel

Ø 0 h sunshine / day

in the selected area
during the cloudiest month selected

Add some buffer

For imperfectly positioned solar panels and lower sun power in the mornings and evenings.

Regular average sunshine duration during the cloudiest month (during your typical stay) in the most cloudy area where you plan to travel/live.

Dont't forget to add some buffer for imperfectly positioned solar panels and lower sun power in the mornings and evenings! Add another 20-40% to take into account that solar panels rarely convert the energy stated on the label even under otherwise very good environement conditions. An example: a 400W system might often convert into somewhere around 250W average in good real life conditions.

Cloudy days

In order to dimension the battery size needed, we need to estimate how many days the batteries need to bridge regulary.

You can use a gasoline or diesel generator as an alternative power supply every now and then to charge your batteries when the weather is exeptionally bad. You can buy a battery charger for regular power outlets (campsites) too. Another option is an alternator charger for charging with the power of your RV engine while driving. These options seem bad at first sight when thinking of the environement but too many unused batteries are worse. You will find these options in step 4.

This will get expensive and un-eco very fast! Having a backup power source might be a good idea anyway.

Use at your own risk!

I can not be held responsible for any data provided, availability, calculation errors, recommendations and any direct or indirect injuries or damage of your power setup, any devices or rv/home/roof and the suroundings.

If you don't agree to the above you have to stop using this calculator and might want to ask a solar system professional.

That being said let's start:

List your electric devices

  • V W Wmax h h
  • V W Wmax h h
  • V W Wmax h h
  • V W Wmax h h

If you don't know what these values are about, nevermind! They might at this stage already give some people a rough idea about the size of their system. But this tool will do all the calculation for you so just go ahead and click the 'next' button!

 Wh / day
power consumption
 Ah / day
electric charge @ 12 V

Electric current sum:  A /  A max

Simultaneous usage of high power equipment

Since you added a few high power devices, configure which of the following you need to use at the same time (only high voltage, 100 W+)
Select as few as you possibly can to keep the required inverter power as low as possible. But keep in mind that you indeed have to otherwise never use them simultaneously.

Select Batteries

These numbers include cloudy days, buffer and all sorts of electrical losses but also depend on the deep cycle of the battery you choose below. So don't be alarmed if they change – especially if you switch between AGM and LiFe batteries.

  • Wh effective energy to store
  •  Ah min. battery capacity required

Key benefits of LiFe batteries are they are lighter, have an extreme low deep cycle max making you require roughly 50% less Ah (size). Also they don't care much about full charging cycles and stuff like that.

On the other hand the way cheaper solar AGM batteries are sufficent in most setups too. Thus for small setups (< 200Ah) in rather constantly good weather or if weight is irrelevant I'd probably just buy a few more or bigger AGM batteries.

If you can afford LiFe batteries go for LiFe. Otherwise just go for the solar AGM ones.

 / Ah effective

 % deep cycle min
cycles lifetime

x x  m

years calculatory lifetime max – calculated in your setup with your usage profile based on cycles lifetime

You will need

of these batteries

It is propably better and easier to have as few as possible separate batteries. Try selecting bigger batteries to reduce the number of batteries you need.

For most batteries, the manufacturers do not provide all data needed. Thus based from the values available I guessed some of the values missing in the data sheets. The values in the dropdown are C100 values (meaning the stated capacity is correct when uncharged during a timespan of 100 hours which might not be the case in your setup). Your selection on max cloudy days in a row determines the number of hours minimum the battery will have to pass back the power. But you can't drain the battery all the way! The minimum should never go below a rest capacity of X% which is battery specific (% in your selection above).

But don't worry the calculation takes all that stuff into account automatically.

Add extra batteries

Want to be extra safe and add even more buffer? – not recommended

Select Solar Panels

  •  W min. required

24 V Panels are said to be more effective in low sun conditions. 12 V Panels require bigger cables to transport the same energy, thus will loose more energy on the way to the battery charger. 24 V panels require a more expensive MPPT charger (in case you use a 12 V Battery setup) but I'd recomment them for the 12V panels too anyway since they are way more effective transfering the energy to your batteries (higher voltage → thinner cables possible and/or less electrical loss). 24 V panels are not available in small dimensions and rarely as a flexible panel.

If you have the space available I'd go for 24 V panels. Otherwise do it like most RV setups and choose 12 V panels.

 / W,  W / m2

  x   x  m

You will need

of the selected panels
→  m2

Add extra panels

Want to be extra safe and add even more buffer?
If you do so you might want to add extra batteries too – depending on your reasons for upgrading.

Space available for panels

 m      x       m

We have to place panels. You need space for more panels!

max.  m2 wasted

The open circuit sum for your solar panel selection in full serial mode would be  V. Many people recommend to connect them in parallel in order to work around problems with partly shaded panels. Thus I will ignore this value and assume you will setup your panels in parallel.

Battery charger

 W solar power min required.

 W max. @  V


 V |  A charger

Suitable for up to  W solar power
from  V panels.

 % loss,  A own consumption

Inverter  V to  V

 W minimum required

 W pure sinus


 W Inverter

pure sinus
 % energy loss

No inverter required.

you did not add any high voltage devices

In case you want to use a laptop, a hairdryer, a toaster or the like, anything high voltage – even when only used from time to time – please add these devices with a calculated average daily hours of usage. Only then we can calculate which inverter size you need. These devices might drastically change requirements for batteries and solar panels too!

Cable sizes required

The lower the voltage and the higher the energy the higher the loss.

Fragile hightech 12 V loads like TVs, computers or cameras should get bigger cables – especially if the cables need to be long (> 2 m / 79"). Because for every meter of cable the voltage drops a little because of the loss effects inside the cable. The bigger the cable the smaller the loss, thus the longer the cable can be without droping the voltage to much.

Values calculated are for aluminum cables. By using copper cables you could reduce all values by 1/3.

Placing everything as close as possible is very important to avoid electrical loss inside the cables. The charger should be directly next to the batteries and next to the inverter. Keep the cables to the solar panels as short as possible and the cable from the charger to your 12 V electrical loads even shorter. 230 / 110 V cables have very low loss so we don't care about the length of these cables at all.

Panels → charger

What is the average distance from where you want to place the battery charger to the solar panels.

*  mm²,  m


*  mm²,  m


 mm² cables required

 % loss
≙ - W for all panels

Do not start to combine cables from different solar panels close to the panels but as short as possible before the battery charger. A combined cable for the full length would need a diameter of  mm² min. in your setup! Solar cables are typically available in 4 and 6 mm²

The bigger battery chargers have 2 or even 3 ports for connecting the solar panels. Thus there might not even be the need to combine the cables at all.

Each pair of cables goes separately all the way from their panel to the charger!

Charger → batteries

*  mm²,  m


*  mm²,  m


At  mm² the loss will already be as high as  %.

 mm² min.

 % loss @ 1 m (= 39") length

Charger → inverter

*  mm²,  m


*  mm²,  m


At  mm² the loss will already be as high as  %. In case you rarely use your high voltage devices, you could go smaller in case it is hard to find cables that big.

 mm² min.

 % loss @ 1 m (= 39") length

Thank you
for using

Please help me keep this project alive. I have to forward a few qualified sales every year to Amazon in order to be allowed to use the Amazon API. The interface provides the data needed (pricing, availability, weights) for us. Without that API this tool would not be possible.

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