Off-Grid Solar Calculator

May 3, 2009

Part of my job over the past couple of years has entailed doing energy sizing for off-grid photo voltaic (PV) solar systems.  To help with this I have relied largely on an excel-based solar calculator that I created.  I thought it might be useful to share.

Please note: this is NOT intended to replace getting a detailed power estimate from a local solar expert who can best take in account the local conditions. This is more intended to help you with estimates when you are looking to bring a project off-grid. Please use at your own risk.

Solar Costing

A common question relating to PV systems is what does it cost?  A technique commonly used is to estimate the cost at $10-per-watt. This includes the cost of the panels, batteries, charge controller and wiring – installed.  A 100W system, for example, would cost you around $1,000.   You can begin to see why we tend to get so nutty about power efficiency! =)

Note: In Africa we’ve found this price to vary widely from $10 to over $15 due to different policies on import taxation, transport costs and varying levels of local competition.  Also, $10-per-watt is for the initial setup of a PV system only.  To consider issues of sustainability, it is important to take in account that batteries will need to be replaced every 2-3 years and the charge controller ever five.  If you wish to factor in replacement costs, to keep the system operational,  $15-per-watt should be used.

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I'm a technologist/geek living in Nairobi, Kenya. I believe open code and data can make the world a better place. Follow me on Twitter;

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