For me the ROI depends a lot of the initial cost.
For CFL I don't care about ROI as I can afford several CFL per month. I think this is my duty and this should be mandatory.
The price for our PV panels is nearly the one of a new car (10% less than a prius) and without the tax credit and the high sale price the ROI would have been 50 years... In these conditions we wouldn't have done it because it would have blocked our other projects during too much time.
The current ROI is 10 years with the first third in 1.5 years. In these conditions this project blocks our other projects by a couple of years.
If your motivation is saving money then I think 5-10 years is OK. If your motivation is ecology then 20 years can be OK. In all cases, the project mustn't block your other projects.
It will also depend on that fact you own your house or not. You can keep your CFL when you move into another house. You will have to let your PV panels when you'll sell your house, but your house will have a more value
Denis.
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Earth absorbs 1.8 t CO2/head/yr, while a French generates 6.2 t CO2/yr
To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.- kg saved 06/08-08/09: 1816.9+382.9 (ecodriving / 1420mi not driven) = 2199.8
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(2.66 kg/l diesel)
- kg saved by 3kWc photo-voltaic solar panels : 187 kg/yr
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(59.1 g/kWh)
Radioactive wastes saved by 3kWc photo-voltaic solar panels :
- Long life (>100,000 years) : 2.85 g/yr (0.9 mg/kWh)
- Short life (<300 years) : 31.7 g/yr (10.0 mg/kWh)
Based upon "official" French figures...