taxation of own-generated solar electricity

[Gambatte 900]

Here my data on a monthly basis, system ca 9kWp, orientation half modules East, the other West. No shadow. Hamburg.

You see a jump in the production at Sept 2020. Hard to believe but true: the installer admitted they had connect only half of the modules  so they came back and got them all connected. 

Very interesting that although the production almost doubled, the self-use improved very little, it means the system is oversized. A good rule-of-thumb is you should have as many kWp as yearly MWh, so for most households 3-5.

[Gambatte 900]

Here some data on a daily basis

[scook17 248]

54 minutes ago, Gambatte said:

Very interesting that although the production almost doubled, the self-use improved very little...

Energy usage peaks in winter, as the lights are on longer, outside water temperature is lower, heating/tv/whatever on longer as its dark outside...

Solar generation goes down over winter, so grid pull goes up.

Even though they connected up more panels, it makes hardly any difference to your winter figures. Interesting to see and east/west system.

 

I figured out after a while, put washing machine/dishwasher on during the day and other measures only get you so far.

Oven/Cooking is still in the evening, Lights, TV etc. I concluded I needed a battery to cover night-time usage.

Your additional grid energy is 75KwH to around 210KWh per month, so between 2.5KWh and 7KWh per day.

Why I also thought of getting a battery system. Seem Sonnen is the only choice now Tesla pulls out.

 

 

[Gambatte 900]

I wrote this several times already:

1) When I got quotations 2yr ago, batteries costef x10 more than the amount they would have lowered my electricity bill

2) they are BAD for environment, because they need to be manufactured transported etc etc  and, unlike PV modules, they don't turn sunshine into electricity, they just change who is going to use the PV electricity, you rather than grid user. I understand most people don't care about stuff being bad for environment, but maybe PV folks should be more sensitive than others.

 

[Gambatte 900]

25 minutes ago, scook17 said:

Interesting to see and east/west system

Most people cannot choose their roof, like us.

South production is of course better.

But East- and West- are better for self use, because production is less peaked at midday but more distributed into mornings and afternoons/evenings, which is actually when you use more electricity.

And east and west allow you to have more modules (tough you probably shouldn't).

[Adem137 180]

Our solar output reduced from 2020 complete year 9,072kWh to 7,383kWh in 2021. Is this normal? As we had a bad summer last year? Or could something be wrong with my solar panels. 

[mako1 864]

The DeutscheWetterDienst (DWD) actually has the data you need to figure out if panels are performing as expected.

The rough optimal estimate 'pi x Daume' calculation could be based on latitude, the angles (plural) of your panels and the panel efficiency. Sun azimuth, etc to determine what is hitting your panels. Great project for geometry nerds (!).

 

DWD free climate data:

https://cdc.dwd.de/portal/

if you drill down, you will find wind, solar, etc data measurement for all of Germany (at the various stations).

You could then get a past history of the solar capacity at the nearest site and use that as your baseline to see if you have issues with your panels or if it was just a below average year.

This assumes that if the measurement site is nearby, your crappy year was also a crappy year there.

[Gambatte 900]

Floating solar panels could be the next big thing in clean energy

 

https://www.popsci.com/environment/floating-solar-energy/

[MikeMelga 7,255]

On 16.2.2022, 13:39:53, Adem137 said:

Our solar output reduced from 2020 complete year 9,072kWh to 7,383kWh in 2021. Is this normal? As we had a bad summer last year? Or could something be wrong with my solar panels. 

That's a 18% drop. Usually new solar panels lose about 1% per year. So degradation does not explain it. Most likely just bad weather. Could also be that one set of panels got disconnected, but AFAIK there is no simple way of testing without physical inspection or plying around with inverter inputs.

[Adem137 180]

On 18/02/2022, 15:14:45, MikeMelga said:

That's a 18% drop. Usually new solar panels lose about 1% per year. So degradation does not explain it. Most likely just bad weather. Could also be that one set of panels got disconnected, but AFAIK there is no simple way of testing without physical inspection or plying around with inverter inputs.

Are there some companies that do servicing of panels, cleaning and inspection etc?

[Gambatte 900]

Maybe you should contact your original installer.

Otherwise some other PV installer in your area. PV installers tend to be electricians (tough ver few electricians work on PV).

Rlectricians "companies" that do also PV normally mention it on their website.

[Frantic 72]

We are visiting some properties to buy and today I knew about a GEG requirement that basically force you, as a new owner purchasing a property, to change oil heating to a different more clean energy source. For other cases the heating system is near to reach the end of life and then, again, it needs to be changed soon.

So being in the situation (we MUST put a new heating system) would it make sense to go PV instead of pellet, heat pump, gas, etc ? My gut is that the answer to this is yes.

Also, reading the news about the taxation (i was reading all the thread till page 5, congrats to all) was for me an huge relief. I am in a situation where i can make my steuerklarung with a software (smartsteuer) and adding 1000 euro of tax consultant just for having a PV plants would have made not that sense.

 

Is it possible to use a PV implant to produce electricity but also warm water ?

[Gambatte 900]

4 hours ago, Frantic said:

We are visiting some properties to buy and today I knew about a GEG requirement that basically force you, as a new owner purchasing a property, to change oil heating to a different more clean energy source. For other cases the heating system is near to reach the end of life and then, again, it needs to be changed soon.

So being in the situation (we MUST put a new heating system) would it make sense to go PV instead of pellet, heat pump, gas, etc ? My gut is that the answer to this is yes.

Also, reading the news about the taxation (i was reading all the thread till page 5, congrats to all) was for me an huge relief. I am in a situation where i can make my steuerklarung with a software (smartsteuer) and adding 1000 euro of tax consultant just for having a PV plants would have made not that sense.

 

Is it possible to use a PV implant to produce electricity but also warm water ?

We built our small house in 2019. We decided at the time to heat with gas, not with Wärmepumpe, because it was cheaper. I have been regretting it ever since. We also installed a large PV, happy about it. I have been gathering data from our PV every day: financially it will pay off and generate a small profit. 

 

On PV batteries:

Do not install a battery, zillions of cunny vendors will tell you otherwise but batteries are a very expensive way to damage the environment.

You trust cunny vendors (dunno if they care about environment, or they ever studied energy), or you trust me (hard core environmentalist and data freak physicist, also home owner with PV)? Take this: if they convince you, they make a fat profit. If I convince you, I win nothing. Your take.

When you most need electricity the battery will be empty (long dark evening after cloudy winter days), and it will full when you barely need it (at night in the summer). And on top of it being useless, they are very expensive. Financially they would be neutral if they were 10 times less expensive. Not 10% cheaper, 10 times cheaper.

Although both PV and Wärmepumpe are good, the contribution of your PV to the electricity needed by the Wärmepumpe will be extremely modest, for the same reason batteries are almost useless: your WP will suck electricity  (winter, or nights) when your PV cannot significantly produce it (winter, nights).

 

Oh, could well be my words did not convince you. If so, let me know and I will send you the mathematical analysis based on the data I have been collecting every day since installing the PV. I'm a data freak, comes from my profession.

 

Good luck with housing. 

 

[MikeMelga 7,255]

34 minutes ago, Gambatte said:

On PV batteries:

When you most need electricity the battery will be empty (long dark evening after cloudy winter days), and it will full when you barely need it (at night in the summer). And on top of it being useless, they are very expensive. Financially they would be neutral if they were 10 times less expensive. Not 10% cheaper, 10 times cheaper.

Battery prices are dropping fast. They are already below 300€/kWh, which is close to the magic number to be worth it from a financial perspective.

 

34 minutes ago, Gambatte said:

Although both PV and Wärmepumpe are good, the contribution of your PV to the electricity needed by the Wärmepumpe will be extremely modest, for the same reason batteries are almost useless: your WP will suck electricity  (winter, or nights) when your PV cannot significantly produce it (winter, nights).

You realize that you can set your Warmepumpe to peak usage at middle of the day?

Also, if you want to consume at night, that's what the battery is there for.

You are also ignoring that EVs will charge at night most of the times.

 

I think batteries don't work for you, but as everything with engineering, a conclusion can shift dramatically based on scenario.

A house with a lot of PVs, warmepump, and 2 EVs will probably benefit from batteries. It's just a matter of scale and when you need the power.

 

 

[fraufruit 41,963]

Some people say they want to be greener but not if it costs money.

[Gambatte 900]

15 minutes ago, MikeMelga said:

Also, if you want to consume at night, that's what the battery is there for.

Winter nights the battery will be empty, too little daytime sunshine to charge it up.

 

Summer nights the battery will be full, plenty of daytime sunshine to charge it up. But the WP will not need to run.

[Gambatte 900]

7 minutes ago, fraufruit said:

Some people say they want to be greener but not if it costs money.

20 minutes ago, MikeMelga said:

 

FF, that was me for example, and I'm very ashamed of my decision. My bad. 

[Gambatte 900]

27 minutes ago, MikeMelga said:

Battery prices are dropping fast. They are already below 300€/kWh, which is close to the magic number to be worth it from a financial perspective.

Our quotes were 10k€ for 10kWh, 1yr ago, x10 overpriced.

3k€ for 10kWh would have been overpriced "only" x3.

 

But we don't have 2EVs.

If you are cheap, you don't drive Tesla, you drive a cheap benzin car.

And if you are green you drive very little, ride the bicycle instead.

[MikeMelga 7,255]

24 minutes ago, Gambatte said:

Winter nights the battery will be empty, too little daytime sunshine to charge it up.

 

Summer nights the battery will be full, plenty of daytime sunshine to charge it up. But the WP will not need to run.

But the Evs will... see how scaling up and diversifying consumption changes the equation?

2x Evs represent probably 75% of yearly consumption. So you do need to target your system for nighttime charging.

[MikeMelga 7,255]

9 minutes ago, Gambatte said:

Our quotes were 10k€ for 10kWh, 1yr ago, x10 overpriced.

3k€ for 10kWh would have been overpriced "only" x3.

 

But we don't have 2EVs.

If you are cheap, you don't drive Tesla, you drive a cheap benzin car.

And if you are green you drive very little, ride the bicycle instead.

Agree, just don't generalize and say batteries are bad. There are scenarios where they are good.

My dream scenario is a very large house in Portugal with 2 EVs, heated pool, heat pump for water and AC. In that scenario, with a consumption well above 10.000kWh per year, it does make sense.

 

And you don't own EVs now, but in a few years you will.