Like i said it was 16 panels 4kw system with Economizer and south facing a huge house with like 5 kids i believe they were spending near 60 a week on Electricity, Economizer is for gas which again cuts the gas bill immensely. Also its a national company of 8 years the calculator is made by the company can not be tweaked, do the maths thats 1440 saved a year before the fit payments etc, then youve got 10 to 12 % of there investment every year, Then the Economizer addition which cuts there gas bill. so straight away just on savings is near 30k in 20 years + the 2 x investment is near 50 so why wouldnt the Economizer give them a extra 9k over 20 years??