hTTi

Installed late 2019, ca 9.5kWp 29modules 13keur, half module East- the other half West-, no shadow, near Hamburg
I am posting this for fun. Maybe someone is interested.

I had more recorded data but ouch a computer glitch and lost them, so starting again and I now have only a shorter recorded period. I will update the figures as I acquire more data.

I also simulated getting a domestic Akku (sorry, no data shown here), the only quotation I got was 10kWh 10keur (vendor said smaller Akku make no sense, and cost would have been almost identical). Over its 20yr lifetime this would have lowered my grid bill by 1keur (NOT per year, but in total over its 20yr!), so a net loss of 9keur. Still a good deal says the vendor Oh, and this assuming the 10keur Akku lasts 20yr as the vendor said, not 10yr as the manufacturer warranted.

Any question, just ask

10kWh 10keur is a rip off. Neither in Munich area they will dare to charge so much

I got my PV system commissioned a pair of days ago. After a lot of thoughts, calculation, simulation, my conclusion (at least in my usage case) is that a 5Kwh battery was ok to have. More would not have been worth.
Here https://www.bonotos.com/ you will find a useful excel file.
Also this is pretty interesting: https://pvtools.sektorsonne.de/

The "problem" in your case is that most probably you will need to change your inverter into an Hybrid one in order to support the Battery. So it is not just the cost of the battery. Maybe in those 10k was included also the new inverter ? Then is not a complete rip off.

I won't get a battery. Bad for environment AND bad for my wallet. And extra hassle.

Ironically, my inverter is actually already compatible with a battery (I know most aren't), I wouldn't need to be changed.

Bear in mind the quotation was 2020, some time ago, perhaps less expensive now, can't be bothered to check again....

It was fantastic observing the vendor trying to convince me that despite the overall financial loss, 9k€ over the 10/20yr battery life, it was a great financial investment.

But @frantic, what battery quotation did you get?

I chose a BYD HVS 5,12 Kwh. 3800euro included installation. Initially I was going for a Huawei one, same size, few hundred euro cheaper. The problem with the Huawei one, at least with the 5kwh size, is that the max throughput would have been 2.5 Kwh. You turn on two fireplace on the induction stove and you start to take part of the electricity from the grid.

Price/Kwh are definitively lower than 4 years ago but we are still at a point where you have to do your own homework to understand if it is worth or not. It is not yet a no brainer decision. You have to consider also that an Hybrid inverter (needed if you install a Battery) cost slighlty more of a normal inverter of the same size.
In our case, our electricity consumption profile justified the battery.
We both work, even when we work from home we hardly can cook dinner during working time.
Regarding dinner, we are not "brotzeit" people, we cook for real (italian and iranian, what can you expect ? ) . Culturally (but working time help on this ) we don't have early dinner time. Dinner time for us is between 20.00-21.00.
If we need to do a washmaschine washing we can do just after work. Lights in the garden at night, TV and computer, at evening and night.

In this first 2 days the battery is doing exactly what we need and we are discharging it each day. The more you "use" (charge/discharge) your battery the more is your return of investment.

All in all according to my calculation, the plus of the battery in our case will be:

1) One year less for return of the complete investment (PV System and Battery).
2) Much more flexibility in how to use electricity. Of course when we can we will try to switch to day time activities that requires electricity.

@Frantic

very interesting, thanks a lot for sharing.
From whom did you buy it and get it installed? Small local company or big name?

In our case definitely Akku not worthed. I wrote it many times: nett loss of 9keur. And this assuming 20yr lifetime the vendor said, if instead the lifetime was 10yr as the manufacturer warrants then the loss would be more.

Sei Italiano anche tu? Oppure tua moglie? Ciao

I got the battery together with the PV System.
I gathered several offers from local companies, I did not want to go with big companies that then hire sub or sub-subcontractor with the risky of no quality check and other crap.
I was asking to each company an offer with and one without battery in order to compare.

Yes I am italian.

The month of May ended, so I'm adding new data.
June is also shown, but just started so of course statistics is not yet good.
Note: percentage-wise, the reduction in grid reliance between Dec and May is much more modest than the corresponding increase PV production. As expected.
I don't have a battery, so the Akku graph is a simulation (based on measured data).

Updated figures, now including also the month of June 2024, which just ended
It also includes the month of July 2024 (scaled by number of days), although it just started.

Do you have a gas heated hot water storage tank? It's possible to redirect excess electricity to the tank to heat the water instead of sending it back to the grid for ¢. It's essentially a water battery.

Edit: they are called solar diverters

alma.freya wrote: ↑Tue Jul 09, 2024 9:45 am Do you have a gas heated hot water storage tank? It's possible to redirect excess electricity to the tank to heat the water instead of sending it back to the grid for ¢. It's essentially a water battery.

Edit: they are called solar diverters

I don't have it, that would be bad.
Right now I sell electricity for ca 10ct/kWh, last time I checked gas costed ca 6ct/kWh, so selling some less electricity in order to buy less gas is a loss.
Beside, there are also purchase and installation cost, as well as enviromental impact of manufacturing and transporting this stuff.
And also: most electricity is sold in summer, when demand for gas is small, and viceversa.

In current installations you normally combine it with a heat pump so you multiply the electricity you put it by a factor of 4x to 5x. But like everything related to solar it will take forever to recoup the investment. Currently there are massives subsidies to promote heat pump installations, but it is happening the same bad effect the subsidies brought to the EVs, they are keeping the prices inflated and companies are pocketing all the money. The magic number for a heat pump installation at the moment is 20k EUR, because that's the maximization of the subsidies.

Frantic wrote: ↑Fri May 03, 2024 11:18 am It is not yet a no brainer decision.

- which it surely should be!!!
We are all living on this planet, and have a vested interest in the planet surviving for many years to come, so, in my opinion, the use of solar energy really is the most obvious way to go - it´s "free", and you can use it for all sorts of things!

Robinson100 wrote: ↑Tue Jul 09, 2024 8:06 pm

Frantic wrote: ↑Fri May 03, 2024 11:18 am It is not yet a no brainer decision.

- which it surely should be!!!
We are all living on this planet, and have a vested interest in the planet surviving for many years to come, so, in my opinion, the use of solar energy really is the most obvious way to go - it´s "free", and you can use it for all sorts of things!

Ok, but my sentence was related to buying or not a battery, not a PV system.

Frantic wrote: ↑Tue Jul 30, 2024 11:48 am Ok, but my sentence was related to buying or not a battery, not a PV system.

Not sure what you meant.
But data I've been collecting since installing my PV some years ago shows that the cost of a domestic Akku is several times the total reduction of our electricity bill over the 20yr Akku lifetime.
Not to speak its environmental harm.

Btw July is almost over. I will soon post updated data, including one more month, July 2025.

Alberto wrote: ↑Tue Jul 30, 2024 10:43 pm

Frantic wrote: ↑Tue Jul 30, 2024 11:48 am Ok, but my sentence was related to buying or not a battery, not a PV system.

Not sure what you meant.

but i was not quoting you

New month, new data freshly measured

How much loss you get when the day is very hot and the panel reach an high temperature ?
In my case (South oriented roof) I should get in these period of the year, between 12:30 and 14:00, my maximum (8Kwh) but when the day is hot and without wind and "fresh air", i get 6.4 Kwh / 7kWh. Around 15-20% loss.
Not sure if this is "normal" or not.

new data, now including August 2024

I just got this offer, and I am tempted to try it out, as the price is breathtakingly low...

https://vendomnia.com/balkonkraftwerk/s ... ertech-fkt

Who can tell me that this is not worth doing it? What's the catch on this?