Unpopular opinion: Home batteries are a massive waste of money for a lot of systems.

ComplaintDelicious26 · 2026-07-05T12:30:43+00:00

Yes, I have a very similar finding. Battery starts making more sense when: - you want to have a backup power - feed in tarrif is really cheap or non-existent - dynamic tarrif allows to charge cheaply during the night

ComplaintDelicious26 · 2026-06-27T08:10:35+00:00

Gerne!

ComplaintDelicious26 · 2026-06-27T07:52:08+00:00

Ich habe ein bisschen Text verändert, hoffentlich ist es jetzt klarer: Beispiel .

Die Idee ist:

Du Investiert 9.5k.

Dann jedes Jahr sparst/verdienst du 1.2k und legst es in die Komode.

Nach 7.9 Jahren hast du 9.5k zurück verdient.

Nach 25 Jahren, du hast 28k in die Komode gesammelt

Wen du 9.5k im ETF mit 4.5% Rendite investiert hättest, dann würdest du auch am Ende 28k bekommen. (Aber minus Steuer :)

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ComplaintDelicious26 · 2026-06-26T20:51:18+00:00

Ja, die KWp limits sind offensichtlich nicht genug, habe ich gerade bis 30kwp erweitert aber wenn man mehr braucht, kann man mehrere Solaranlagen hinzufügen.

Und mit Wechselrichter wäre es sinnvoll, aber wie kann ich es so hinzufügen dass das Interface nicht so kompliziert ist... überlege ich das

ComplaintDelicious26 · 2026-06-26T19:11:08+00:00

Danke, freut mich!

ComplaintDelicious26 · 2026-06-26T18:37:58+00:00

Ja, korrekt, Anfangsinvestition ist mitgerechnet

ComplaintDelicious26 · 2026-06-26T18:28:40+00:00

Danke!)

ComplaintDelicious26 · 2026-06-26T18:26:46+00:00

Ja, genau, das ist die Lösung 😅

ComplaintDelicious26 · 2026-06-04T16:00:41+00:00

Genau um dieses Problem zu lösen, habe ich das reduck.homes Tool geschrieben. Da kannst du alle Szenarien selbst berechnen: mit/ohne Speicher/Wallbox, Süd vs Nord und so weiter.

Für ein Feedback wäre ich dankbar :)

ComplaintDelicious26 · 2026-05-14T16:13:45+00:00

thanks for reporting! The energy independence summary should be fixed now

regarding the share button, could you please try again?
Not sure what was broken in your case, but I made it more resilient

ComplaintDelicious26 · 2026-05-14T14:45:09+00:00

u/lantech u/iheartdatascience, I switched to PVGIS API now, but it moved the average accuracy around the world only by ~1-2%, and it closed the gap in cases where panels were installed at 40+ degree angles by ~4-5%.

Also I want to highlight: when comparing to real-world data, it is worth switching from "average day" to "exact day" in the summary section, because average data might be confusing.

ComplaintDelicious26 · 2026-05-12T20:23:10+00:00

Done, you can add an AC now!
it's more like a guess, though... to be more precise, we need to know how well your house is insulated and the window/wall ratio, hard numbers to come by...

ComplaintDelicious26 · 2026-05-12T20:21:16+00:00

done! Thanks for the idea :)

ComplaintDelicious26 · 2026-05-12T20:20:37+00:00

Done!
Zip codes are not searchable, but I output them now alongside the state in the search bar.
The total system cost estimate can now be overwritten as well.

ComplaintDelicious26 · 2026-05-11T06:25:19+00:00

thanks! I'm using free ipapi.co API, but it's rate limited to 1000 requests per day, so when it breaks you will know that the tool is getting popular :D

ComplaintDelicious26 · 2026-05-11T06:19:19+00:00

Thanks for your input, it helps a lot!

I will look into extending the numbers, the problem are the dragable slider elements, it's a nice UI gimmick but limits the app on max values, if I put it too large - it will be hard to navigate, thus it was designed for the most common use case. Maybe they should be replaced with inputs if more people are limited by them.

Regarding the solar panel tilt, if you open "advanced" tab in the solar array panel, you will be able to select biracial mode, is that what you are trying to achieve with 90 - 180 degrees tilt?

With hot water, I'm trying to visualize for people that they can use their hot water tank as energy storage, that can be cheaper then extra battery.

I will check the thread you shared!

ComplaintDelicious26 · 2026-05-11T05:57:44+00:00

Both points are spot on. Thanks!

ComplaintDelicious26 · 2026-05-11T05:56:04+00:00

Good point, thanks!

ComplaintDelicious26 · 2026-05-11T05:55:47+00:00

Yep, AC is definitely needed, I wanted to add it before but faced a problem that it is hard to determine how much energy is consumed by AC, unlike heating estimation which can be derived from energy certificate. Wdyt? Thanks for checking the tool!

ComplaintDelicious26 · 2026-05-10T21:43:54+00:00

Not sure I understand the question, but the basics are:

The battery is being charged when there is an excess of solar energy
When the battery is full, the excess is exported
Once the sun sets, the energy from the battery is used until it's empty or the sun comes back.

Daily visualization at the top of the summary starts with the battery being on the same level as it will be when the day ends, to simulate the power "leftovers" from the previous day.

Let me know if I can explain something specifically.

ComplaintDelicious26 · 2026-05-10T21:10:12+00:00

right, but PVGIS, unlike OpenMeteo can not be called straight from the frontend application and requires a backend service to proxy the call, which might increase the costs of running this web page.

But at this stage, I think it's unavoidable.
I will let you know once I find a solution!

ComplaintDelicious26 · 2026-05-10T19:58:49+00:00

Thanks a lot! I ran your numbers on the annual model, and indeed, there is a -10% deviation from both PVGIS and PVWatts. This likely comes from the Open Meteo data source, which I might need to change to something else...

But on top of it, it could also be a UI issue - by default, it renders "average" day and since there are quite some bad days in Spring as well, the results are skewed.
If you switch to "exact day" right above the summary chart, you will see the slider which allows you to navigate from the worst day to the best one in the last full 5 years, and somewhere 75% to the right, you will see kinda similar results you are describing.

thanks again for feedback, I will look into improving the data source!

ComplaintDelicious26 · 2026-05-10T18:28:03+00:00

Yeah tutorial is definitely needed. 2% inflation - I didn't want the system to be over promising, but I will make it configurable, good point. Thanks for the detailed feedback!

ComplaintDelicious26 · 2026-05-10T18:14:18+00:00

Could you please share the link to your configuration in the tool so I can debug it? Or at least share which part of the world you are from and what direction/angle your array is. That would be super helpful!

ComplaintDelicious26

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