hmm.
There's a few things I'm not happy with in there...
Performance estimates are basically just an updating of the flawed SAP methods and are only marginally better, but fiendishly complex - they're certainly not going to stop any of the dodgy lying gits in the shiny suits from lying through their teeth about performance estimates then going bust before the liability claims roll in. As I read this they're at best around 15-20% accurate once you take into account the +/- 10% accuracy of the shading estimate, and the 15-20% varation from the average sunlight levels there is for our region (East Penines) between the east coast, and the Penine areas.
Fair enough if companies don't have a better system than this, then make them use this method, but it's ridiculous to make companies give greater prominance to such a flawed methodology than to a far more sophisticated and accurate method using 3d modelling for shading impact, and PVGIS for highly accurate localised sunlight and temperature data.
It also severely penalises those using more efficient inverter set ups as it makes no allowance for this at all that I can see, yet there can be a 5% performance advantage between an old style inverter and the latest high efficiency TL inverters operating at the peak efficiency point. The shading factor also makes no allowances for inverters with shading functions, or micro inverters, or system designs with dual trackers and correctly orinetated panels to minimise the shading impact, it's just a one size fits all package that means all companies will have to estimate the same output from all system designs, which will put more costly but better performing systems at a distinct disadvantage.
TBH I'm pretty well minded to tell them that we're going to refuse to comply with this guidance as we don't think companies should be penalised for using better equipment, better system designs, and much more accurate methods of producing performance estimates. Let's see them make that one stick in court if they dared to take it that far.
