Not a DIYer...solar now + possible Powerwall later

[frontrangeleaf]

...at least not when it comes to crawling around on my roof - I fell off a ladder 3 years ago and broke my back. Thankfully, I'm not paralyzed. So no DIY solar projects for me. We have limited roof area and quite a few trees around, all of which are not in my yard.

Which brings me to the system we're considering purchasing, on the north end of Denver.

18 REC Alpha Pure Black 400 panels
18 Enphase IQ 8A microinverters

Installed by Photon Brothers, a local guy. They warrant their work 25 years, including all roof penetrations.
Projected cost installed after incentives and cash discounts: $2.70/w. Should make 113% of our last year's consumption.

These are twinned heterojunction panels that carry a 25 yr production warranty at 92% of rated power. The inverters are also warranted 25 yrs. Thermal coefficient is low. Wind and snow ratings are reasonably high if not standard setting. We'll have the option of adding a storage battery at a later date without changing this first phase of the system build-out.

Compared to the other offers we've had, this seems reasonable. Tesla is way cheaper, but also not at the same quality level. You also have all the "Tesla brain damage" that comes with dealing with them. Some folks love 'em, and others not so much. I've spoken with several Tesla solar owners personally, and have come away with a non-confidence-inspiring impression. To be fair, those systems are all 7-9 years old. That said, I'm still not inclined to go with Tesla.

 

[goldbrick]

Is the $2.70/W cost before any tax rebates? There are still good rebates to be had and I think they actually go up in 2023 due to the recently passed IRA.

In any case, I get why you don't want to DIY and I'm sure you will enjoy having the solar. Having someone else do the work just increases the payback time but whether you hire it out or DIY it's still a 'can't lose' investment. Hopefully the shading issues aren't too severe.

 

[user 24513]

One anecdotal experience with the micro-inverters: a neighbor has a system using them and they have been a real problem, some have actually fallen off and are visible sitting on the roofing below the panels, others have stopped sending their current. The panels need to come off to check on them.....so do a careful deep dive into that system before committing.

 

[frontrangeleaf]

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.>

Edit: This is last false - Xcel offers 1:1 net metering in our state if you choose the right billing option.

Thoughts?

 

[frontrangeleaf]

Is the $2.70/W cost before any tax rebates? There are still good rebates to be had and I think they actually go up in 2023 due to the recently passed IRA.

In any case, I get why you don't want to DIY and I'm sure you will enjoy having the solar. Having someone else do the work just increases the payback time but whether you hire it out or DIY it's still a 'can't lose' investment. Hopefully the shading issues aren't too severe.

That is correct. We will be able to take full advantage of the new rebates, now as well as in the future when we add a battery. You no longer have to do the full system all at once.

 

[johnlocke]

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.

Thoughts?

Generally speaking , battery backup costs too much to ever pay for itself even with TOU rates and government subsidies. If you're buying backup for outages, figure on 12 hours with whatever you need to have powered on. Then add 20% to allow for days when you can only partially charge batteries. If you only need a couple of hours or just need UPS for grid hiccups, then it's a lot cheaper. In reality, a back up generator is cheaper for most people. I happen to have both only because I live a high fire risk zone and SDG&E was willing to pay for the battery backup as mitigation for frequent power shutoffs. On the other hand, I'm still trying to get the grant money from SDG&E to pay for it. You have to install the system before applying for the grant. That insures that fewer people actually do it.

 

[user 24513]

We have about 3.5 kWh of backup battery, more than we have ever needed for the occasional outage since we can immediately stop using most of the power and just let the freezer and fridge (and yes the modem) run until power is restored. The electricity runs through an Outback inverter which switches from grid to battery in 1/60 of a second so nothing is even aware of the outage. This is an expensive solution no doubt but is a holdover from our decades off-grid and we like the peace of mind.

 

[frontrangeleaf]

So our project is moving along nicely. Loan approved, site survey done, in design now.

Photon Brothers and the credit union so far have been exemplary with their service. I am impressed, which is not an easy thing to do.

I've been reading up on the Powerwall 2, and am currently considering a "phase II" build out, perhaps next year, to add storage if the price is at all reasonable (not sure what that means yet, frankly...).

I'm leaning toward "a modest battery, but enough storage to be useful." Then wait a bit, and see what happens with bidirectional chargers - opens the Chad de Mo v CCS discussion, among other considerations, so not right now, but I see Wallbox has the Quasar for the Leaf, and Fermata tells me they'll offer a homeowner's version for single phase 240v in 2023. There are also a couple of others.

I am intrigued by the option to use the Powerwall as part of a Virtual Power Plant. There are several pilots running in Colorado, and of course, California has been busy in this respect. For example: https://www.nrel.gov/news/features/2019/small-colorado-utility-sets-national-renewable-electricity-example-using-nrel-algorithms.html

Anyone out there have experience with VPP and their storage system?

 

[frontrangeleaf]

Quick update: We finally have what I've been calling "phase 2" installed and up and running. We ended up going with a single Tesla Powerwall 2, and added 3 additional east-facing panels to our garage roof after tracking actual production and usage for a few months. The new panels are sufficient to pick up the house load at baseline and leave a bit extra to begin charging the battery in the early morning hours from sunrise to around 10am, when the larger west-facing arrays begin producing notable power.

After this upgrade, we now have:
18 west-facing REC panels as noted above
3 east-facing REC panels
21 Enphase IQ8A micro inverters
1 Tesla Powerwall 2
1 Tesla Backup Gateway 2

We moved the AC and car charging circuits to a non-backup panel. The rest of the house circuits are all backed up. This was easy to do as our home was built with a meter panel outside and a sub panel with the house branch circuits inside the garage, mounted back-to-back. All 200 amp service.

At baseline, the battery can carry the house for 16-20 hours unassisted. This means that we can run 85-90% independent of the grid ~8 months out of the year, depending on weather conditions, without working at it much. I've set the battery to keep 50% in reserve, and run in self-consumption mode. Since we have 1:1 net metering and ample credits, moving to time of use doesn't really matter much right now.

So far the system is working as advertised, and we're quite pleased. As things turned out, less than a month after we stood up the upgrades, there was an extreme high wind event coupled with a red flag fire warning, which caused our local power utility to cut power to 55k people just immediately north of us. (A first in our area, but what I had been expecting since the Marshall fire 3 years ago.) Another 95k people lost power as a result of the storm, some for 3 days. So, I'm feeling a little less silly about having made this investment, even though in this case we didn't lose power in our neighborhood.

Not the cheapest solution to be sure. We still have some edge cases to test, but so far, it's been worth it.

We had another brief power outage over the weekend, and I didn't even notice until I looked at my phone. Transitions to/from the grid have been seamless.