# #15 How many solar power and battery capacity do I need?

This answer is quite simple because you can simply calculate it.

A solar panel supplies 12V and in our latitudes you can expect an average of about 4-5 hours of yield per day. Based on this, you can calculate with 400 Wh or 33,33 Ah per 100 Watt solar panel. So that you can save your pencil, I have created an Excel sheet where you simply have to enter the values of the consumers in the green fields and you can see at the top right at “Überschuß” whether the targeted total wattage of your solar system is sufficient.

Before you start scribbling on a paper simply download my excel sheet for this calculation. You only have to enter the devices watt and current. Be sure that you calculate with 12V even if you use a 230V device with a converter because the converter works with 12V. Also be sure to know the max Ampere your battery can provide. An example: You have a converter and use your mini oven with 1500 watt for 30 minutes. This means that you need 125 Ampere for 30 minutes. The simple calculation will give you a result of 62,5 Ah but you can be sure to blow a 62,5 Ah battery away if you try this. So don´t do this if you don´t want to meet the guys from your local fire department. Always have in mind what kind of battery you use (AGM or LiFePo?) and you need to know what your kind of battery can deliver!!