Quote:
Originally Posted by muffildy
Estimated pay off:
3500$/{(7kw/day)*(13c/kwh)*250days/year} = 15.4 years
So it pays for itself a little bit faster than if i did a grid tie in system which typically pay off themselves in 20-25 years.
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In your math you show 250 days in a year, not 365... so a pay back of 10.5 years if your electric rates never go up, if you do this as a grid tie system then you are getting every bit of that power being used instead of it being lost as soon as you unhook your car and if you use micro inverters then you get the MPPT optimized for each panel so each panel is putting out it's peek, often above rated out put and extending the sun hours in a day because of how MPPT works, so less then 10 years if you don't have shading on your site.
Now the question is, what is the pay back on that gasoline that you bought over the last ten years? because charging with solar brakes even after 8 years or less compared to buying gasoline and that is even after hiring someone else to install them!