Offgrid Solar Configurator
We need to estimate how much sunshine you can expect to dimension the solar panel size.
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.
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
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.
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
x x m
years calculatory lifetime max – calculated in your setup with your usage profile based on cycles lifetime
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
W solar power min required.
% loss, A own consumption
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.
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
Charger → inverter