6% below the estimate is well within the range of performance that could be expected from an MCS estimate, the estimates are based on regional data, and within each region there can be +/-10% variation from the average depending if you're in a more hilly rain affected part of the region or the sunniest part.*
Without checking it's hard to know for sure, but I'd suspect that you should be at or above the average slightly where you are though.
I suspect it's probably a combination of most of the factors I've discussed, plus the seagull droppings etc all causing small reductions in output that add up to the reduction you're seeing.
Whether it's worth replacing the inverter or anything else before it dies a natual death is debatable, you'll need to do the maths on something like an £800 cost for a new inverter vs the maybe 3-4% best case performance improvement you're likely to see from it and see whether the figures stack up for you or not.
*this is an issue I've been attempting to sort out with the MCS steering group since the new performance estimation method was put in place, with no success to date.
Without checking it's hard to know for sure, but I'd suspect that you should be at or above the average slightly where you are though.
I suspect it's probably a combination of most of the factors I've discussed, plus the seagull droppings etc all causing small reductions in output that add up to the reduction you're seeing.
Whether it's worth replacing the inverter or anything else before it dies a natual death is debatable, you'll need to do the maths on something like an £800 cost for a new inverter vs the maybe 3-4% best case performance improvement you're likely to see from it and see whether the figures stack up for you or not.
*this is an issue I've been attempting to sort out with the MCS steering group since the new performance estimation method was put in place, with no success to date.