frontrangeleaf wrote: ↑Thu Sep 01, 2022 10:39 am
Thanks for the feedback guys. We have the best warranty that I've seen in writing. These local guys have been around for quite a while, and the reviews have been really quite good. They appear to stand by their work.
Given the shading issues we have, microinverters seem like a definite plus, as is the "twinned" layout - half-cut cells wired into 2 sub-panels, so that if one half is shaded, the other half can remain on full power. It does introduce 18 points of failure in the microinverters, but none critical path.
The $/w figure is after federal rebates and cash discounts as noted in my original post. We'll have the system fully paid for in 3 years (not leasing) - it's basically what a nicer used car used to cost, pre-pandemic, to us out of pocket, so not too unreasonable. Payback period depends a lot on future Xcel rates, which have been going up pretty quickly in recent years. That part is basically a roll of the dice in my mind - I'm not looking at this from a strictly financial point of view. Since buying the Leaf and adding AC for the house our consumption has gone up quite a bit. I'd like to not be too big a part of the overall problem, so to speak.
Edit: We do pay Xcel a small surcharge every month to support wind power as well. In theory, all of our power "comes from" wind source.
I am beginning to ponder phase II, which would involve adding a battery after we get the panels paid for. I want to see how production actually shakes out before dropping more $$. I am forecasting that our power system may gradually grow less reliable due to climate change and possibly political factors in the coming years. I'd like to insulate us from that to some extent. The drought is already causing havoc behind the scenes.
What is the best way to approach a battery backup conceptually? Clearly, step 1 is get clear about what problem you're trying to solve, and no, I'm not there yet. That said, is there a useful way to think about the problem in general?
Enphase is selling LiFeP storage batteries using the same microinverter series in 3.3 kWh and 10 kWh sizes. Our consumption is currently about 600 kWh/month, and the array will be rated to 7.2 kw, expected to produce a minimum of 7500 kWh/year per projections given shading and our location. That suggests using very rough numbers that the 10k would offer roughly 1/2 day of backup. My guess is that would be more than adequate.
Our habits will no doubt change when we begin to escape TOU billing during the day. I haven't thought that through entirely either.
Today, we charge the car exclusively overnight when rates are quite a bit lower, and use the AC almost exclusively overnight as well - we chill the house down while it's cool outside overnight (Denver's lows are typically in the 60's despite 90-100 during the day). Our house is well enough insulated to coast through the heat of the day, and we bought a reasonably efficient variable speed compressor based AC unit. I can imagine setting the Leaf to charge slower during the day and taking advantage of the solar. The opportunity cost of not charging on Xcel far exceeds their wholesale rate during the day.