Solar vs grid cost

mountainman said:

@Estragon much cheaper that a $35000 sewer system.

mountainman said:

I'm sure it would be more efficient. 120 dc to 120 or 240 ac. Would you use 60 2 volt batteries or 20 6 volt?

Photowhit said:

Well,  for  what it's worth, I'm  still happy to contend that my off grid system is now cheaper than the grid, in my location. I   do make some minimal sacrifices to make this happen. I don't use  a backup generator.  I  will reduce my  use about every  2-3 years usually in the  late fall when we have  an inordinately long cloudy period.  Grid  electric here is  very expensive for a minimal user.   It now costs $39 for the privilege of buying  electric  from the COOP.



I use around  4 kWhs a day during the  winter months and 12-15 during  the summer running air conditioning along with the fridge and daily stuff.

In my situation, much of the energy used in the summer is directly off the array, our heat comes with sun. I have minimal storage, just a 16 kWh battery.

My system cost a bit less than $10K, and since  I'm running the numbers raw here, I'll add in the $1K to install a wood stove, but not add in the yearly costs for that since it isn't off set by electric costs and would be viable heating method without solar.

So  my cost is 11,000  for the solar electric system,  replacement costs will be inverter and charge controllers every 10 years at  $2500 (even  though I have been using the same inverter for 15 years and the charge controllers seam to be doing well 8  years in), and replace the forklift battery every 12 years, (I had originally used 15, I think that is viable, but I want to use as realistic numbers as possible, mine is hanging in there even though it was poisoned  early and it's 8 years old now.)

So with a 30 year life of the array(it will still be usable after than and have some residual value) the initial cost was 11K+$5kfor electronics 2X and $5K for replacement forklift battery 1.5X (though the original battery cost was $2250 delivered it is very close to the same today, it was sized for my cabin, and I will replace it with a 50% larger one),  the cost over 30years will be around $21,000.

The current cost of grid electric to replace would be $39 x 12 = $468 + $172.80 (14.40x8months at 4kWhs a day) and $192($48x4months)=$832.80 per year x 30 years = $24,948.

I have mentioned the residual value of the array, but not included the $2K tax credit. There is some nominal cost of distilled water as well as lost interest. It does  take some minimal amount of time, I spend perhaps as much as 2 hours a month on the system.

Several things collide to make this inexpensive. I don't need a lot of storage using much o the energy directly off the array. I have a very good energy use profile for solar. My local energy cost from the grid is quite high. I just did total numbers, but 120 kwhs a month for 8 months is 960 kWhs, add 1200 for the summer months, the total usage is around 2160 kWhs, and the total cost is $832.80, so $.385 a kWh.  Using these slightly higher numbers than previously, my cost off grid is about $700 a year for 2160 kWhs or about $.325 a kWh. Originally I had figured about 26 cents a kWh and is likely not far off if the lower actual costs and the tax credit are included.

I have 'played' a bit.  I bought the inverter I  had spec'd to use this year, and it is installed but not more than trial run (I'm too lazy to build a 4/0 cable for it, mostly involves getting my bench vise installed again to use my hammer crimper) I've added none of the original extra panels yet, but have 1K of others ($250) on the frame and 4 of the others mounted but not wired. I still need to do a rerunning of the original numbers, but they will just be cheaper as I think I originally spec'd a new inverter, not a $600 used one (4000 watt magnum, was going to wait until the battery change over and switch to a 48 volt system)