we've been doing that for the last 2 years, though at 95% and only for the first year, and not using SAP. Not had to pay out once yet, and our 1 year old systems are averaging around 3% over, which is pretty much bang on the money as we build in about 2-3% leeway into the figures anyway.
eta - though our guarantee does have the proviso that we're not responsible if the reduction is down to variations in solar output that year, which Evo don't seem to be doing. Either they know that the SAP calcs are underestimating by so much that they're safe even from the up to 8% annual variance from the mean in solar irradiation, or they're planning to use the actual 5 year average and hoping that should even things out, or they're risking a hefty bill a few years down the line through no fault of their own.
still good to see someone else putting their money where their mouth is on the estimates.
