As part of our new build, we plan to install a photovoltaic system on the roof. The roof area is approximately 160sqm (1,720 sq ft), with a pitch of 25 degrees, a gable roof with one side facing northeast and the other southwest. Since we are both civil servants and income from photovoltaic systems requires approval and may later be counted towards our pension, feed-in is not an option for us.
The system is intended solely to reduce our electricity consumption. We will have a ground-source heat pump with a borehole, a 300l (80 gallons) hot water storage tank, and a ventilation system for heating. The house is designed to meet KFW 55 standard (higher efficiency is no longer possible due to the basement).
Since I am home starting at midday, appliances such as the washing machine, dryer, dishwasher, and others will mainly be used during the day.
Additionally, we live in an area with above-average sunshine and fewer cloudy days, even in winter.
We do not want a battery storage system yet, even though this means we will occasionally export surplus electricity. Once batteries become more affordable, we plan to add one later.
How should the system be sized for our needs?
The system is intended solely to reduce our electricity consumption. We will have a ground-source heat pump with a borehole, a 300l (80 gallons) hot water storage tank, and a ventilation system for heating. The house is designed to meet KFW 55 standard (higher efficiency is no longer possible due to the basement).
Since I am home starting at midday, appliances such as the washing machine, dryer, dishwasher, and others will mainly be used during the day.
Additionally, we live in an area with above-average sunshine and fewer cloudy days, even in winter.
We do not want a battery storage system yet, even though this means we will occasionally export surplus electricity. Once batteries become more affordable, we plan to add one later.
How should the system be sized for our needs?
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toxicmolotof13 Mar 2017 21:00Or a pool in the garden... and the energy consumption already rises from 30% to 60%.
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Evolution14829 Mar 2017 14:54I don’t understand why battery storage is spoken of so negatively here. It always depends on the level of self-sufficiency you want to achieve. Whether for ecological or economic reasons doesn’t really matter at first; fundamentally, a battery simply offers more options to use the electricity you produce instead of feeding it back into the grid.
The storage batteries are not being criticized unfairly; they simply are not worth their current price. I have several concrete offers for my system now, and depending on the model/provider, the cost per kWh extracted from the battery roughly ranges between €0.50 and €1.00. This is two to three times as much as what you pay for grid electricity, depending on the supplier’s tariff and usage type. I really wanted one of these units myself, but no manufacturer guarantees more than 5,000 to 6,000 charge cycles, and if you base a real full cost calculation on that, you could easily afford to have firewood delivered for 10 years as extra expenses, massively reducing the electricity costs of the heat pump during winter heating, and you’d also have a cozy flickering fire in the fireplace every evening from November to March. At least burning money this way is enjoyable!
For now, I have stepped back from the idea of installing a battery; I am preparing the photovoltaic system for a later retrofit and will wait about five years to see if these units become available at reasonable prices. Only then will I make a decision. Such a photovoltaic system does not necessarily have to generate a profit, but it should not destroy money either—and that is exactly what every battery does at today’s prices.
For now, I have stepped back from the idea of installing a battery; I am preparing the photovoltaic system for a later retrofit and will wait about five years to see if these units become available at reasonable prices. Only then will I make a decision. Such a photovoltaic system does not necessarily have to generate a profit, but it should not destroy money either—and that is exactly what every battery does at today’s prices.
Evolution148 schrieb:
I don’t understand why battery storage is spoken of so negatively here. It always depends on the level of self-sufficiency you want to achieve. Whether for ecological or economic reasons doesn’t matter at first; fundamentally, a battery simply offers more options to use the electricity you generate instead of feeding it into the grid.If your financial resources are unlimited and therefore not an issue, that is true. Otherwise, not.
Storage is uneconomical unless special circumstances arise through subsidies. So, it remains something to be viewed as a hobby, and hobbies are allowed to cost money.
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toxicmolotof29 Mar 2017 20:31Evolution148 schrieb:
I don’t understand why battery storage is spoken of so negatively here.They are not being spoken of negatively. From an ecological perspective, they might (perhaps) be great. I wouldn’t dare to make an environmental assessment comparing saved [insert energy source here] against manufacturing costs (including the extraction of rare earth materials)...
But as soon as you do an economic calculation based on real data, you will realize that every kWh from the battery costs you at least 40 cents. If your grid electricity is more expensive, then the battery actually makes economic sense.
If not, it’s probably not a matter of speaking negatively.
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Evolution14813 Apr 2017 11:24Alex85 schrieb:
Energy storage is uneconomical unless there are specific conditions created by subsidies. It is precisely the subsidies that are uneconomical; the only ones who benefit from them are the banks. You have to commit to limiting the output of the photovoltaic system, provide proof of proper commissioning, and above all, finance everything through a loan from the KfW, whose interest payments over the years end up consuming the repayment grant.
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