Since my inport-export meter was installed by ESB Networks in February 2011, I have imported 2242 and exported 1918 units (kWh). This would indicate that I am 86% self-sufficient. However I think this is a bit flattering as this is at the end of summer and I prefer to use a rolling 12-month indicator = [output/(import + own use)] where (import + own use) represents total home electricity usage. The actual figures currently are 1234/(1644 + 253) which is 65% – still not bad! As I log PV output and export data daily in a spreadsheet, ‘own use’ comes from this and is simply output kWh less exported kWh.