What is the best software to design an off grid solar power system?

For a stand alone Solar power system I would  not opt for a soft ware. Best practice I would go for is Manual calculation. The results are great. For large Hybrids and on grids yes you can develop a software which can help and save time.

At Off-Grid Energy Australia we use our own custom built software made specifically for stand alone system design. We are able to quickly enter all user data to formulate an accurate and technically compliant system with easy to understand system performance figures.

This technically advanced and leading software technolgy specific to off-grid applications ensures greater accuracy in designing system choices that are right for your situation and future needs.