taxation of own-generated solar electricity

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Do you have a heatpump? Your total consumption of 5500kWh/yr seems high otherwise. We are 3, bake or roast every day, wife works from home, and we use ca 2400kWh/yr.

 

In sunny summer days your panels would fill up the battery. But in those days (and night) your consumption from the grid is very limited anyway (especially with heatpump), so you would not end up using most of the energy you store in the battery.

And in winter you take much electricity from the grid. But even if you had a battery you would not exploit it, because the electricity produced by the panels in winter is very limited anyway, can't charge up the battery significanlty.

I had winter days with tot. consumption 8,5kWh, and tot. PV production 0,5kWh, sure a 10kWh battery was not going to be charged.

And I had days when I took 1kWh from the grid, and I sold to the grid 25kWh of PV electricity, again a battery of any size would not have helped much.

 

Can you obtain data for your panels not on a yearly basis but on a daily basis (I can for mine, going back to the day the system was set up)? Then you can better simulate how much you could charge the battery every day, and how much of its capacity you end up using. It takes a very simple script in your fav language, even Excel can do it. This would give a more realistic expectation of the usefulness of the battery. After I did this I learnt that even if battery prices were 25% of what they are today they would still be overpriced.

 

In short: don't do the math using yearly data, but rather using 365 consecutive sets of daily data.

 

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2 hours ago, Gambatte said:

Do you have a heatpump? Your total consumption of 5500kWh/yr seems high otherwise. We are 3, bake or roast every day, wife works from home, and we use ca 2400kWh/yr.

I was doing around 4500kWh/y before I had my EV... family of 3. Of course, multiple computers, 2 fridges, etc. All lights are LED, so it's not lighting. We cook every day, with induction, oven and airfryer.

 

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3 hours ago, scook17 said:

 

2019 - Produced 6374 KWh of which 4266 was sent to the grid. So we used 2108 Kwh ourselves, around 33%.

 

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2020 - Produced 6577 KWh of which 4269 was sent to the grid. So we used 2308 Kwh ourselves, around 35%.

Doesn't it mean that you saved(/reduced) €590 (2108*.28) & €646 your electricity bill for 2019 and 2020 year respectively if you have used the same amount of electricity without solar? May I ask how much was the installation cost in 2017? 

 

 

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Keep in mind there is always income tax on the PV electricity you produce (both: the one you sell, and the one you use yourself).

And unless you opt for Kleinunternehmer (which has pros and cons) there is also Vat, again both ways: the electricity you sell to the grid as well as the one you "sell to yourself".

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22 hours ago, vivanco said:

 

Doesn't it mean that you saved(/reduced) €590 (2108*.28) & €646 your electricity bill for 2019 and 2020 year respectively if you have used the same amount of electricity without solar? May I ask how much was the installation cost in 2017? 

 

 

 

Yes, if you use the figures of 2019 and 2020, and multiply by 0.28 Euros per KWh, yes it works out that just having solar panels reduced the electricity bill by  €590 (2108*.28) & €646 in those years. Projecting that over 20 years, the claimed lifetime would give you a (618 Euro average) 12,360 Euros, so some 18K over the max lifespan, say 30 years. After claiming back the MWST on the cost, it was around that cost to install. Add in the amount you get paid for the surplus electricity (after tax), so plus 275 Euros and break even period is around 14 years. I am guessing I somewhat overpaid for such a system, but I knew little at that time, hence sharing some real data for those considering this.

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23 hours ago, Gambatte said:

Keep in mind there is always income tax on the PV electricity you produce (both: the one you sell, and the one you use yourself).

And unless you opt for Kleinunternehmer (which has pros and cons) there is also Vat, again both ways: the electricity you sell to the grid as well as the one you "sell to yourself".

Bl00dy hell, that was news to me. I was aware that I'd have to pay tax if I sold it back to the grid (after all that's an income), but it beggars belief to me that I'd have to pay tax and Vat on solar power generated for my own use, from a system bought and paid for myself. 

By the way, how is that even controlled? 

Would that also apply to stand alone systems? I currently have one very small solar panel, which I use for trickle charging the batteries of my tractor and lawnmower over the winter (so not connected to any other system, battery or even an inverter). It works so well, I was considering getting a larger system to power everything in a shed, or even extending the roof to get a dozen or so panels up there and produce more electricity. Having to pay tax on that energy would make it much less attractive. 

 

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1 hour ago, dstanners said:

Bl00dy hell, that was news to me. I was aware that I'd have to pay tax if I sold it back to the grid (after all that's an income), but it beggars belief to me that I'd have to pay tax and Vat on solar power generated for my own use, from a system bought and paid for myself. 

Welcome to the club😀.

I wonder why these are the details vendors always "forget" to mention.🤣😂

 

You could also ask how to calculate the tax on the solar electricity you "sell to yourself". After all there is no exchange of money. Well, fact is the FA has their own way to calculate this, very perverse and lot of "fun" to learn 🤣😱🥺😬...

 

The best place to discuss anything photovoltaic is the forum I linked earlier. In German. People are very nice knowledgeable and helpful. And there are tax and finance experts too.

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40 minutes ago, Gambatte said:

You could also ask how to calculate the tax on the solar electricity you "sell to yourself". After all there is no exchange of money. Well, fact is the FA has their own way to calculate this, very perverse and lot of "fun" to learn 🤣😱🥺😬...

So if one uses 100 kw of your own energy, at which rate does FA assumes? 28 cents that one buy from grid or 9 cents that one sell to the grid?

 

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On 10/02/2021, 15:39:32, scook17 said:

 

 

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To make it even weirder: unless KUR (Kleinunternehmer), there are two types of taxes on your self used electricity : income tax and Vat. These are taxes on the very same "good", the electricity you sell to yourself.

Say your own income tax rate is 30% for example, and Vat is 19%.

You would expect if the value of your own used electricity is A, then Vat and income tax are 0,19*A, and 0,3*A.

Right?

Wrong.

For vat the value of own used electricity is calculated differently than for income tax. So Vat is 0,19*A, and income tax is 0,3*B, with A and B different. Although A and B refer to the very SAME electricity, the kWh you produced and used yourself.

 

Just to make it more fun (=complicated).

This is Germany, let's not forget 🤣

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40 minutes ago, Gambatte said:

To make it even weirder: unless KUR (Kleinunternehmer), there are two types of taxes on your self used electricity : income tax and Vat. These are taxes on the very same "good", the electricity you sell to yourself.

Say your own income tax rate is 30% for example, and Vat is 19%.

You would expect if the value of your own used electricity is A, then Vat and income tax are 0,19*A, and 0,3*A.

Right?

Wrong.

For vat the value of own used electricity is calculated differently than for income tax. So Vat is 0,19*A, and income tax is 0,3*B, with A and B different. Although A and B refer to the very SAME electricity, the kWh you produced and used yourself.

 

Just to make it more fun (=complicated).

This is Germany, let's not forget 🤣

True. Things need to be extra complicated in Germany. 

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On 2/10/2021, 4:05:00, Gambatte said:

Do you have a heatpump? Your total consumption of 5500kWh/yr seems high otherwise. We are 3, bake or roast every day, wife works from home, and we use ca 2400kWh/yr.

 

In sunny summer days your panels would fill up the battery. But in those days (and night) your consumption from the grid is very limited anyway (especially with heatpump), so you would not end up using most of the energy you store in the battery.

And in winter you take much electricity from the grid. But even if you had a battery you would not exploit it, because the electricity produced by the panels in winter is very limited anyway, can't charge up the battery significanlty.

I had winter days with tot. consumption 8,5kWh, and tot. PV production 0,5kWh, sure a 10kWh battery was not going to be charged.

And I had days when I took 1kWh from the grid, and I sold to the grid 25kWh of PV electricity, again a battery of any size would not have helped much.

 

Can you obtain data for your panels not on a yearly basis but on a daily basis (I can for mine, going back to the day the system was set up)? Then you can better simulate how much you could charge the battery every day, and how much of its capacity you end up using. It takes a very simple script in your fav language, even Excel can do it. This would give a more realistic expectation of the usefulness of the battery. After I did this I learnt that even if battery prices were 25% of what they are today they would still be overpriced.

 

In short: don't do the math using yearly data, but rather using 365 consecutive sets of daily data.

 

Use 2400KWh or draw an additional 2400KWhrs? Baking is 2.5Kw to 3.5Kw I would guess, so 2.5x365 = 912Kwh by itself.

Sure you can use an instant pot (pressure cooker), microwave, small over, rice cooker or whatever, but cooking does take power for sure.

 

Been gradually replacing exensive items, mainly old items with A+++ (as many pluses as possible...) items.

Some of my findings:

- Replace any old fridge or freezer. We had an old freezer (presumably faulty) drawing 400-500KWh/year. New one is around 130 KWh/year. They run at night so are 50/50 day vs (expensive if you have solar and no battery) nightime electricity.

- Replace old TVs. Our new TV is bigger, better and draws less power than the old plama one we had.

- Connect the dishwasher to the hot water, not the cold water. Around 80% of the usage is heating the water. A modern one uses around 800w-1Kw per cycle, so let's say 900w, or around 330KWh per year, so 260 or so is spent on heating the water. This can be done with a heatpump or gas. By the time is mixes with a little cold water in the pipe, it's around 40C or so. Dishwashers use 45C to 70C, so this reduces the heating cycle (and time) considerably.

- Invest in some sockets which turn stuff off when the master socket turns off. Use for TVs, computers etc.

- Computer network equipment uses a lot of power if left on all the time. My 10w network switch uses 87KWh per year (around 26 Euros if using grid power) if left on 24/7 all year. Ditto NAS, wifi points, switches etc.

- Replace any multi-monitor setup with a single widescreen monitor. Get rid of those 10+ year old, but still working monitors. They draw (each) maybe 100w...

- Replace the tower computer with a laptop. Typically these use 20-30w, where as the tower one is 100-150w.

- Kind of obvious, but replace all light bulbs with LEDs.

- Don't use electricity for heating. Gas is ~4c and electricity, ~30c, so even with the heat pump, it's only cheaper if the heat pump is powered by solar.

- Use a plug which does measuring and has a timer. Personally I like the TP-Link HS110.

- When buying a dishwasher or wachine machine, buy one with a timer or delayed start function so you can set it before leaving for work. Not that, that's an issue as I now work from home all the time.

- I never found any reasonably bright outdoor solar lights, so outside lighting if needed seems to need to be via a mains transformer.

- Throw away the kettle and buy an instant hot water heater, or just use a nespresso and don't add the coffee capsule. I often drink coffee and boiling the kettle for one cup does seem a waste.

- I reused and old android tablet as a display, for the web interface from the inverter which displays the solar energy being generated and put it somewhere easy to see, not down in the basement. You can of course just look out the window, but it's nice to see the number...

- My amplifier for the TV was using 30w in standby (yes it's old). Before the various EU directives banned such things, there was lots of old kit which did this. Satellite, TV cable boxes etc.

 

So about winter, yes, charging a battery maybe hard. But really just the months of November to January mainly with this issue. So in Dec we had 131KwH, but I guess we'd have used 170Kwh (at 5.5KWh/day). In November we had 266 but in January just 103 KWh. As you say, you get days with almost zero, the one or two days with 10+KWs which easily fill the battery within a day. Even with a 10KWh battery (Telsa power wall is 13.5) you can find yourself giving power to the grid unless you happen to have an E-Car to fill up just at the right time.

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6 hours ago, scook17 said:

Use 2400KWh or draw an additional 2400KWhrs? 

Used 2400kWh, as I wrote.

After all why does one install PV? To save money and environment? If so lowering consumption is a better measure in this direction.

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When I installed my PV I also toyed with the idea of battery. But I was skeptical about making much use of it. So I waited 1yr, and after I collected daily electricity data for 365 consecutive days (no need to write them down by hand every day of course, the Wechselrichter provides all past data), I calculated how much we would have charged and used the battery EVERY day. That's how I reached the conclusion that now batteries are still hugely overpriced. Not based on the average household, or gut feeling, or year average, or guesses, or what the vendors or random strangers say. Based on the data I measured for my household.

 

 

8 hours ago, scook17 said:

- Don't use electricity for heating. Gas is ~4c and electricity, ~30c, so even with the heat pump, it's only cheaper if the heat pump is powered by solar.

WRONG.

Heat pump are expensive to install but very cheap to run. Of course 1kWh of electricity costs more than 1kWh of gas. But if the heatpump puts 1kWh of heat into your house it takes LESS than 1kWh of electricity, because the rest comes from the cold air outside, that's why they are named "heatpump", because they pump heat from the cold outdoor to the warm indoor.

 

 

 

 

 

 

 

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17 minutes ago, Gambatte said:

When I installed my PV I also toyed with the idea of battery. But I was skeptical about making much use of it. So I waited 1yr, and after I collected daily electricity data for 365 consecutive days (no need to write them down by hand every day of course, the Wechselrichter provides all past data), I calculated how much we would have charged and used the battery EVERY day. That's how I reached the conclusion that now batteries are still hugely overpriced. Not based on gut feeling, or year average, or guesses, or what the vendors or random strangers say. Based on the data I measured for my household.

 

 

WRONG.

Heat pump are expensive to install but very cheap to run. Of course 1kWh of electricity costs more than 1kWh of gas. But if the heatpump puts 1kWh of heat into your house it takes LESS than 1kWh of electricity, because the rest comes from the cold air outside, that's why they are cold "heatpump", because they move heat from the cold outdoor to the warm indoor.

 

 

 

 

 

 

 

Here is my evaluation of this choice. Heatpumps are rated by COP tells you what ratio of enegy they consumer to what they produce in terms of heat. A typical air source heat pump as we have is rated with a COP of around 3. Thus for ever 1KWh consumed, it produces 3KWh of heat into the hot water. At this rate it takes roughly 10 to 12 hours to heat the hot water by itself if your turn off the electical water heater 'backup'. The electrical water backup is simply a 1.5KW heating element and the heatpump unit alone is about 500w, so on overall heating of 3KW. Unit can be switch to either heatpump or gas, but not gas as the backup. The backup can be turned off.

 

Now in summer, COP increases and in winter it falls. So maybe it goes between 2 and 4, I don't know, but there is at least some variability from what I understand depending on if it's 30C, 0C or -10C outside like this morning. I understand it can go as low as 1, i.e. pass through.

 

The total load measured at the input for 2019 was 1405 KWh, when set to heatpump only over the year, so an average of 117KWh per month, probably more in winter as the outside water temperature is somewhat colder. Now in the 3 months of winter, that's between 50% and 100% of the generated electricity. However, the load is constant, so if the sun shines and you get briefly 2KWh, it still uses just 500w for the heater. Conversely if there is a clould and it drops to 250w, it draws from the grid to make up the missing power. Because it takes so long to heat the water by itself, it's consuming energy during the morning and evening. In summer this is solar, but in winter, this is grid power.

 

In winter, using half or more of the available power for water heating means the other applicances draw from the grid. Whilst in summer, there is a surplus of energy, so this is sometimes the case, in morning or evening, but happens rarely if you try to put appliances like dishwashers, washing machines etc on during the day.

 

Cost wise, gas is 4c and the electricity I sell (after paying tax) is worth 6.7c to me. Given I maybe get a COP of 3, I can divide that by 3, so 2.2c with a COP of 3, 3.35c if the COP falls to 2, or the full 6.7c if the COP is near one. But if you add in some proportion of the 30c paid for grid electricity, you easily start to equal or exceed the costs compared to gas water heating. Thus only in the summer, when COP is high and there is enough power to cover the entire heating period, does it become cheaper to use our heat pump.

 

There are solutions like the UK Zappi charger products which vary the load to match the sun generation on a real time basis, so you could add a plain old electrical element to the heater to use the 'spare' electricity. I plan to do this if I ever get an e-car, as it's the same problem. The load remains constant regardless of the sun energy coming in. Thus you can either balance the load, or use a home battery to balance out the generation vs load peaks.

 

Thus in conclusion, for the summer months, when anyway we switch off the gas heating, I use the heat pump, and the remaing part of the year, switch over the gas. I guess this is around 4 months on electric, around 6 on gas. This mostly matches the switch from long sun hours to shorter ones.

 

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@scook17, why do you have both gas and heatpump? I never heard of household having both. In fact, one of the benefit of heatpump should be that when building the house you save on the gas connection (>1keur), and you save on the yearly gas Grundgebuhr (another like 100eur/yr).

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Hi @scook17

Are you talking about a standard water tank - as a lot of houses already have?

Or a large (  > 1000litr ) tank to act as a "battery" for your excess elec?

 

Following all these ideas and checking our personal pros & cons  as we are planning too 

Thanks!!

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