FAQ: energy loss on solar cables for parallel panel connection

Question: I want to connect solar panels in parallel. What should I keep in mind?

Answer: For a typical 240 WP panel, the MPP voltage is 30V and the current is 8 Amps. If you connect the panels in parallel, the voltage will be the same (30V) and the current will increase. For two panels you get 16 Amps, for 3 panels you get 24 Amps. 

However it is important to keep in mind that the loss of energy is growing with the square of current: W = R * I ^2.  If you increase the current two-times, the loss of energy will increase 4 times (2^2 = 2x2 = 4) , if you increase  the current 3 times, the loss of energy will increase 9 times  (3^2 = 3x3 = 9).

For example if you have a cabling with the resistance of  0.1Ohm, with the flowing current of 8 Amps , you will loose  some 6 watts of energy on the cabling. With 16Amps you will loose some 26 Watts and with 24 Amps you will loose some 58 Watts of energy. 

That is why for the parallel connection, it is very important to use proper copper cables with thick diameters to reduce the energy loss. 

For grid-connected installations it is advantage to place the MicroInverters right to the panels. This helps to avoid the energy loss.