Re:California grid set record of 97% renewable power on April 3
by FPGAhacker on Wednesday April 20, 2022 @11:17PM
(#31105715)
The fact that the return is not compounding makes a very large difference here.
$16,500 returning 10% of the original principle per year isn’t a great investment. 25 years you have $41,000 + 25 yr old solar panels.
$16,500 returning 10% compounding over 25 years gets you $162,000 + the $16,500 principle.
Considering opportunity cost spread evenly over 25 years, those panels cost over $5000 per year.
There are plenty of reasons to go solar, but return on investment is not one of them.
Re:California grid set record of 97% renewable power on April 3
by mrep on Thursday April 21, 2022 @03:40AM
(#31106898)
You are ignoring investing the savings which if the stock market returns 8% vs the panels at 13%, you would get a 50% higher return with the panels + investing the savings in the stock market vs just the stock market after 30 years. Albeit, it does take 13 years to come out ahead.
>>> x = 0
>>> for y in range(0,30):
... x *= 1.08
... x += 2125
... print(y, x)
...
0 2125.0
1 4420.0
2 6898.6
3 9575.488000000001
4 12466.527040000003
5 15588.849203200003
6 18960.957139456004
7 22602.833710612485
8 26536.060407461486
9 30783.945240058405
10 35371.66085926308
11 40326.39372800413
12 45677.50522624446
13 51456.705644344016
14 57698.24209589154
15 64439.10146356287
16 71719.2295806479
17 79581.76794709972
18 88073.30938286771
19 97244.17413349713
20 107148.70806417691
21 117845.60470931107
22 129398.25308605596
23 141875.11333294044
24 155350.1223995757
25 169903.13219154175
26 185620.3827668651
27 202595.01338821434
28 220927.6144592715
29 240726.82361601325
>>> x = 16500
>>> for y in range(0,30):
... x *= 1.08
... print(y, x)
...
0 17820.0
1 19245.600000000002
2 20785.248000000003
3 22448.067840000003
4 24243.913267200005
5 26183.426328576006
6 28278.100434862088
7 30540.348469651057
8 32983.57634722314
9 35622.26245500099
10 38472.04345140108
11 41549.806927513164
12 44873.79148171422
13 48463.69480025137
14 52340.79038427148
15 56528.0536150132
16 61050.29790421426
17 65934.32173655141
18 71209.06747547553
19 76905.79287351358
20 83058.25630339466
21 89702.91680766625
22 96879.15015227956
23 104629.48216446194
24 112999.8407376189
25 122039.82799662842
26 131803.0142363587
27 142347.25537526738
28 153735.0358052888
29 166033.8386697119
Re:California grid set record of 97% renewable power on April 3
by ninjinxo on Wednesday April 20, 2022 @11:54PM
(#31105898)
You're not adjusting for inflation (cash + increases in electricity costs), ambitiously assuming an equivalent 10% return on other investments, or re-investing the amount saved per year in your calculations (that $1650 you save in the first year also compounds to ~$16.25k).
Make those fixes and the numbers are much closer.
Re:California grid set record of 97% renewable power on April 3
by tdhoot on Thursday April 21, 2022 @02:57AM
(#31106691)
Just take the money you save on electricity and put it into the market...?
- 6.4 kW (16x400W panels), microinverter-based (little to no maintenance expected in 25 years)
- estimated to produce 8,500 kWh in year 1
- the panels are warrantied to produce 86% in year 25. Let's use 80% as a more conservative estimate.
- up front cost: $16,500 after the federal tax incentive
- alternative: paying PG&E $.25/kWh on average (conservative estimate)
To a first approximation, the system would save $2,125 in the first year, or almost 13% of the initial investment. In year 25, we'd expect 6,800 kWh. At the same energy price, it'd be saving 10% of the initial investment. (This doesn't take into account inflation, changes in energy prices, and I'm sure other things. This is all very different if your local utility doesn't offer net metering, too.)
The system breaks even in year 8, similar to what others in this thread have reported. But you can also look at it as a pretty low-risk investment returning 10-13% per year for 25 years. That sounds pretty good to me.