Additional costs equal ZERO

Hi,
So it is clear that the additional costs, i.e. operating costs, cannot be reduced to zero, but the goal is, I think everyone wants this, to keep the operating costs as low as possible.
I tried to calculate a few average values.
The photovoltaic system with 23m² module area and 30kwp (maximum something), south orientation and 45° roof pitch should generate about 2700kwh per year. At 25 cents/kwh that is 675€.
If I feed electricity into the grid and simultaneously draw electricity from the grid, I pay 16 cents/kwh but also receive 25 cents. But if the electricity only goes in one direction (1. feeding in / 2. consumption) I either get 1. 25 cents or 2. pay 25 cents.

A 3-person household consumes on average about 3200kwh. At 25 cents that is 800€ per year.

The air-water heat pump consumes on average 5000kwh at 16 cents that makes 800€.

Summary:
800€ heat pump
+800€ household electricity
=1600€
- 675€ offset from the photovoltaic system (revenue from feeding into the grid)
=925€ electricity costs per year
which is about 77€ per month

Would this theoretical calculation be correct?
If anyone has information, an example would be nice.

Best regards

Forget the approach. You are forgetting the investment costs. What good would it do you to actually have operating costs = 0 if you had to invest hundreds of thousands for it?

The photovoltaic system gives you money. (The electricity goes to the utility company, not you). So forget your electricity consumption for a moment and consider the photovoltaic system entirely on its own.

The photovoltaic system costs a lot of money. Economically speaking, you get a return on the photovoltaic system investment of about 5-7%, depending on subsidies, purchase price, and repair needs. You would have to look up current figures. It’s profitable, the question is whether a home builder has that much money available to put a valuable asset on the roof. Normally, when building a house, you sell your assets to use the capital for construction.

As an electricity supplier, the system is no use to you, as mentioned, the electricity does not go to your devices but to the utility company. The electricity is generated in summer, primarily at midday. The air heat pump needs electricity when the water is heated, i.e., bathing times in the morning and evening as well as heating in winter. It’s not enough for cooking anyway. You would need batteries. Large ones...

If you want to save even more energy, then heat your water differently, geothermal heat pump or solar system with heating support, but an air heat pump and controlled residential ventilation with heat recovery is already a great way.

More efficient refrigerator or washing machine, induction cooktop, etc. also still have potential.

Hello

Hi,
So I tried to calculate some average values.
The photovoltaic system with 23m² module area and a 30kwp (maximum something), south orientation and 45° roof pitch should generate about 2700kwh per year.

Well, the numbers are unfortunately not quite right:
(1) With 23m² you definitely won't get a power of 30kWp – 3kWp is much more realistic (depends on the modules used)
(2) there is no "maximum something" in photovoltaics – the "maximums" are the available area and the available capital – nothing else ;)
(3) how much electricity you can generate with a certain system capacity mainly depends on your place of residence. Here in the Ruhr area, you can expect 850 kWh/kWp (which means with a 3kWp system on average 2550 kWh/a), in Munich you can calculate with about 980 kWh/kWp (=2940kWh/a). The feed-in tariff in 2011 is 28.74 Ct/kWh (=733 euros/a in the Ruhr area / 845 euros/a in Munich)

At 25 cents/kwh that makes 675€.
If I feed electricity into the grid and draw electricity from the grid at the same time, I pay 16 cents/kwh but also receive 25 cents at the same time.

16 Ct? Where is there such an electricity price anymore today??
Here with us I pay 21 Ct and already got the letter that electricity prices will be "adjusted" again on 1.1.2012...

But if the electricity only goes in one direction (1. feeding in / 2. drawing) I get 1. 25 cents or 2. I pay 25 cents.

:confused:

A 3-person household consumes on average about 3200kwh. At 25 cents that makes 800€ per year.
The air-water heat pump consumes on average 5000kwh at 16 cents, that makes 800€.
Summary:
800€ heat pump
+800€ household electricity
=1600€
- 675€ offset by the photovoltaic system (income from feeding electricity into the grid)
=925€ electricity costs per year
makes about 77€ per month
Would this theoretical calculation be correct?
If anyone has figures, an example wouldn’t be bad.
Best regards

Yes, this calculation is roughly correct. What is missing: self-consumption.
You have the option to use your self-generated electricity yourself. If you consume up to 30% of your electricity yourself, you get 12.36 Ct for it, if you consume more than 30% yourself, you get 16.74 Ct.
Whether the self-consumption regulation is worthwhile varies for each individual. In our case, very little electricity is used during the day, since no one is at home. However, if you have your office in the house and work from there, you have a higher electricity consumption during the day... So simply analyze your own user behavior.

An exemplary profitability consideration can also be found here:


@Gartenbau:
What do operating costs of "0" bring me? Well, if I have to spend 100 euros per month for energy (electricity, heat) and my photovoltaic system brings 100 euros/month into the cash register and cost 10,000 euros, then the system is amortized after 8.3 years and from then on I start to save – namely 100 euros/month = 1,200 euros/a
I find that very tempting :D

Greetings
Micha :cool:

...The air-water heat pump consumes on average 5000kwh

How do you come to that conclusion?? Both the demand and the consumption depend on the specific individual conditions. With inadequate planning, the difference between demand and consumption for air heat pumps is unfortunately significantly smaller than expected. Only with precisely and meticulously planned systems does one achieve an annual performance factor of about 3.5!

Best regards

...An exemplary economic feasibility analysis can also be found here:...

There are quite different problems lurking here, which are hardly compensable with photovoltaic whitewashing!

Best regards.

@Gartenbau: What do operating costs of "0" bring me? Well, if I have to spend 100 euros per month on energy (electricity, heating) and my photovoltaic system brings in 100 euros/month and cost 10,000 euros, then the system is amortized after 8.3 years and from then on I start saving - namely 100 euros/month = 1,200 euros/year. I find that very tempting :D Regards Micha :cool:

For operating costs = 0 you need more than just a photovoltaic system. At least a heating type like a geothermal heat pump. These are not free. The photovoltaic system that covers all your electricity needs also requires more than just a few panels for 10,000 euros. You can confidently cover your roof and fill your basement with batteries for the rainy season. The problem with renewable energies is that everyone believes they save huge amounts with an investment of a few thousand euros. The opposite is true. Which doesn’t mean it’s all bad. Ecologically it may make sense. Financially, only rarely.