I just finished with the ground mount, grid tied, solar install at my passive house.
My 3200 square foot duplex uses a total of 11,000 kWh per year (and its all electric). I just installed 8 panels which are about 230 watts each, total 1840 watts (1.84 kW). Meaning: if the sun shines at the perfect angle on all panels for one hour straight, I make 1.84 kWh.
By my estimation, I should shave about 12 percent off of my annual energy bill, $185 per year or $15.50 per month. I have about $1600 in the panels, say another $250 in the mount I fabricated myself, $1100 for the Sunnyboy 3.0 inverter. AEP charged $319 for the new net meter.
So if my math is correct (not counting my labor) I won’t start making any money back for 17.5 years give or take.
OK, now I am sorry I put all that on paper. But the solar array looks really cool in my yard. The point I would make here is work to lower the home’s energy use as much as possible, then start throwing solar at it.
On the flip side, I also just finished (almost) our shipping container house. This small house has 900 watts of solar panels, a solar charge controller and inverter charging 8 batteries which are 186 amp hour at 24V. OFF grid.
So far so good. I think someone (maybe two people) could live in this comfortably as long as you also supply about $200 of propane annually (propane for main heat, cooking, and hot water). Also you need clear sun angle and you must be vigilant in your angle changes twice a month to maximize the solar capture. This assumption is very dependent on the life style of the ‘users’ of the energy.
I do hope that information is useful.
Jason Morosko is a Certified Passive House Consultant and Vice President of Engineering at Ultimate Air Inc. in Athens.