So many different investment return figures, which you use?

[Tiberius]

I know in the end it doesnt matter as the disclaimer says you might make zero but seems to be so many calculators and different companys giving different quote figures for the FIT investment figure so wondering which do YOU use personally? Or how do you work it out?

for example a £1000 per year total benefit system:
1. the Energy Saving Trust calculator does todays figures and times it by 25years so 25*1000=£25K
2. others calculators and software include energy price and inflation over the years so the figure may work out at £32K
3. certain companies (ones on the TV particular) are going on that because the elec provider puts them up by 9% then they use 9% per annum and return figures are closer to £38K-£40K

Also anyone come across thousands different in quoted return? not good to give a quote and for someone else to stick couple of grand on theirs rightly or wrongly for you to look an idiot.

 

[BruceB]

I normally include x3 estimates of performance. In increasing order they are normally SAP then PVGIS then Sunny Design. I then use the biggest (Sunny Design) in calculating payback period and ROI. I justify that to myself because almost without exception in the reports of array performance I have read, people have been meeting or exceeding forecast values.

Edit: sorry misread, you are asking about a slightly different issue. I have seen quotes with payback figures that are inflated annually and then added up. That to my mind is a completely false way of looking at it. As the rates are due to be increased by rpi they are already at a common base in Net Present Value terms and for doing a Discounted Cash Flow analysis. But the people who do it probably have no idea of what NPV means.

 

[Tiberius]

Cheers for that, sorry if OP was poorly explain but glad you got the point i was trying to make, might use those 3 like you do in near future.

 

[docka]

Edit: sorry misread, you are asking about a slightly different issue. I have seen quotes with payback figures that are inflated annually and then added up. That to my mind is a completely false way of looking at it. As the rates are due to be increased by rpi they are already at a common base in Net Present Value terms and for doing a Discounted Cash Flow analysis. But the people who do it probably have no idea of what NPV means.

Bruce, I'd like to understand more about NPV and the way you outline your accumulated total payback, can you steer me to some good reading material please?