- Thread starter Eco Deal
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yes. We include detailed PV GIS estimates, using actual inverter and cable loss figures from sunny design, plus fairly accurate estimates of shading losses from the 3d modelling we do.
We guarantee these to within 5%, and so far they've been very accurate.
We included the SAP estimates with a warning about how useless they are, and that our performance guarantee doesn't apply to the sap estimates.
We guarantee these to within 5%, and so far they've been very accurate.
We included the SAP estimates with a warning about how useless they are, and that our performance guarantee doesn't apply to the sap estimates.
We do something similar but you have to be careful. You have to make sure that you're not giving other calculations more weight than the SAP figures.
To be honest, I simply copy the details from the PV Sol calcs directly into tables that I have made with InDesign. Takes some time if I'm totally honest.
I'll happily defend any action MCS wanted to take against us for supplying more accurate performance figures to our customers and offering a 5% performance guarantee against them, particularly in light of the Which investigation last year that specifically highlighted SAP estimates as being inadequate and misleading (or words to that affect).
We have enough data now to be confident about the accuracy of our estimates, and the inaccuracy of SAP.
they're free to argue that point in court, as I say I'd be happy to defend it and am more comfortable issuing realistic performance estimates with a performance guarantee than using seriously flawed methodology just because some quango says we must.
Personally I'm of the opinion that they should force all installers to issue performance guarantees for their estimates if they want to standardise the situation. That ought to concentrate a few minds.
Oddly enough we've do about 10% of our work in Inverness (family connections), and for installations up there SAP estimates are generally wildly optimistic. It's one thing to know you're underestimating the systems performance as in southern England with SAP, quite another to know that you're seriously over estimating performance as we would be in Inverness.
Personally I'm of the opinion that they should force all installers to issue performance guarantees for their estimates if they want to standardise the situation. That ought to concentrate a few minds.
Oddly enough we've do about 10% of our work in Inverness (family connections), and for installations up there SAP estimates are generally wildly optimistic. It's one thing to know you're underestimating the systems performance as in southern England with SAP, quite another to know that you're seriously over estimating performance as we would be in Inverness.
I've never considered that before but it sounds like a superb idea. How does your guarantee work? Is it averaged out so that a good year will compensate for a bad year?
We have found that some SAP estimates work out better than PV Sol estimates if orientation and shading become and issue, even in the Midlands. The shading calculation for SAP is utterly pathetic so with realistic modelling it can actually surprise you how much the shading affects the system.
the guarantee is based on met office insolation levels, so providing annual insolation levels are at or above average, we guarantee that the system will generate within -5% of its estimated output (not the sap estimate), so if it underperformed by 6% we'd return either return 1% of the original installation price, or take remedial action to improve the output, then return the money if that doesn't have the desired impact.
Because we tailor the estimate fairly precisely for each system including the estimates of the shading impact (which we can model for each our of each month through the year if needed), with the inverter and cable losses for that system supplied by sunny design, we can get the estimate pretty accurate, although we tend to leave a 2-3% margin for error to be on the safe side (if a panel is rated at +-3% tolerance we also reduce the estimate by 3%).
It also helps us to really minimise the shading impact on any system by carefully design of the system. I'm not sure how detailed this facility is in PV Sol - we#d developed our own 3d modelling and shading estimation system before we were really aware of PV Sol's capabilities in this area (or IIRC we tried PV Sol and weren't that impressed at that stage, so just developed our own system.)
Because we tailor the estimate fairly precisely for each system including the estimates of the shading impact (which we can model for each our of each month through the year if needed), with the inverter and cable losses for that system supplied by sunny design, we can get the estimate pretty accurate, although we tend to leave a 2-3% margin for error to be on the safe side (if a panel is rated at +-3% tolerance we also reduce the estimate by 3%).
It also helps us to really minimise the shading impact on any system by carefully design of the system. I'm not sure how detailed this facility is in PV Sol - we#d developed our own 3d modelling and shading estimation system before we were really aware of PV Sol's capabilities in this area (or IIRC we tried PV Sol and weren't that impressed at that stage, so just developed our own system.)
the guarantee only applies to the first year performance, as once a year's worth of data has been collected it should be obvious if it meets our estimates or not.
Only if there is a problem and we take action to resolve it after year one would the guarantee extend any further - ie if we made alterations to the system to improve it's performance we'd then take the next years data as demonstrating if it was capable of performing as predicted, or if a refund was in order.
We do include 0.8% reduction in output per year in our 25 year estimator, but our guarantee doesn't apply here beyond the manufacturers guarantee, as it would all end up far too complex and there are too many factors beyond our control such as panel cleaning, trees not being kept trimmed etc.
Only if there is a problem and we take action to resolve it after year one would the guarantee extend any further - ie if we made alterations to the system to improve it's performance we'd then take the next years data as demonstrating if it was capable of performing as predicted, or if a refund was in order.
We do include 0.8% reduction in output per year in our 25 year estimator, but our guarantee doesn't apply here beyond the manufacturers guarantee, as it would all end up far too complex and there are too many factors beyond our control such as panel cleaning, trees not being kept trimmed etc.
Changing tack slightly, I was wondering how much paperwork people actually give to a customer. Our system is to give a verbal "guide price" towards the end of the visit and then go away to check measurements etc. We then produce a formal quotation with production and payback calcs which we either post (usually) or hand-deliver (occasionally) to the customer.
Some customers say, however, that we overload them with paperwork. A quotation envelope to the customer will contain the following:
1) Quotation for customer to retain - contains SAP 2009 calcs, estimated payback info and warranty details (usually 4 sides)
2) Order form containing the main details of the quotation for the customer to sign (2 sides)
3) Cancellation form (1 side)
4) Info from manufacturer about panels (usually 1 side)
5) Info from manufacturer about inverter (usually 1 side)
6) Terms and conditions - based on REAL template (8 sides)
Fortunately we have a printer which will print on both sides of the page but the poor customer has to wade his/her way through about 17 pages. I do prefer to hand-deliver the quotation and explain what all the documents are about but it's often a lengthy journey which I'd rather not make.
Is this overkill or do some of you provide additional information or do things differently? Would it be reasonable, for example, to email customers the Terms and Conditions and provide a printed copy later on if they decided to proceed?
Some customers say, however, that we overload them with paperwork. A quotation envelope to the customer will contain the following:
1) Quotation for customer to retain - contains SAP 2009 calcs, estimated payback info and warranty details (usually 4 sides)
2) Order form containing the main details of the quotation for the customer to sign (2 sides)
3) Cancellation form (1 side)
4) Info from manufacturer about panels (usually 1 side)
5) Info from manufacturer about inverter (usually 1 side)
6) Terms and conditions - based on REAL template (8 sides)
Fortunately we have a printer which will print on both sides of the page but the poor customer has to wade his/her way through about 17 pages. I do prefer to hand-deliver the quotation and explain what all the documents are about but it's often a lengthy journey which I'd rather not make.
Is this overkill or do some of you provide additional information or do things differently? Would it be reasonable, for example, to email customers the Terms and Conditions and provide a printed copy later on if they decided to proceed?
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