Google's Project Sunroof -- NPV correct?

[velocistar237]

Google has introduced Project Sunroof to help people understand their solar options.

Here's an example.

In the example, the up-front cost is $20K.

Go down to the bottom and click "Show detailed estimates." Under "Total 20-year savings" it says the NPV is $23.7K with a 4% discount rate.

Sure, $23.7K > $20K, but with a discount rate that reflected typical stock market returns, wouldn't it be a loss? I thought solar was supposed to have a decent payback. What am I missing?

[karmatroll]

Your understanding of NPV is a little incorrect.  NPV means that solar cells will earn you $23K in today's dollars taking into account the 20K investment you'll have to make.

So it's not that 23K>20K it's 23K>0K

[velocistar237]

Your understanding of NPV is a little incorrect.  NPV means that solar cells will earn you $23K in today's dollars taking into account the 20K investment you'll have to make.

So it's not that 23K>20K it's 23K>0K

Thanks, I should have known that. Net means benefit minus cost. I was thrown off by the similarity in the numbers.