ᐅ Quote for photovoltaic system including battery storage – storage yes/no?
Created on: 8 Sep 2024 16:53
H
haus_bau2025
Hello everyone,
My wife and I are currently planning to build our single-family home of about 140 m2 (1,507 sq ft) and are considering whether to build it to KfW 40 standard or not (mainly for cost reasons). We have received an offer from our construction company for a photovoltaic system with 6 kWp and a high-voltage battery from Varta with 6.5 kWh (6.5 kWh) storage capacity, costing around 18,000 euros. Since the battery alone costs nearly 6,000 euros, and I recall reading here in the forum that many people reject a battery because a) it is too expensive and b) it would be better to invest in additional photovoltaic modules instead, I wanted to ask how you would approach this situation. The plan also includes installing an air-to-water heat pump with central, decentralized, or controlled mechanical ventilation (we are still considering these options as well).
1.) Would you remove the battery and replace it with more photovoltaic modules? If yes, how much kWp capacity would you recommend for a single-family home built to KfW 40/55 standard with "normal use," i.e., occasional home office?
2.) Or would you keep the battery and increase the photovoltaic system capacity with additional modules?
Do you have any other ideas or suggestions regarding what we should pay attention to in connection with the photovoltaic system?
My wife and I are currently planning to build our single-family home of about 140 m2 (1,507 sq ft) and are considering whether to build it to KfW 40 standard or not (mainly for cost reasons). We have received an offer from our construction company for a photovoltaic system with 6 kWp and a high-voltage battery from Varta with 6.5 kWh (6.5 kWh) storage capacity, costing around 18,000 euros. Since the battery alone costs nearly 6,000 euros, and I recall reading here in the forum that many people reject a battery because a) it is too expensive and b) it would be better to invest in additional photovoltaic modules instead, I wanted to ask how you would approach this situation. The plan also includes installing an air-to-water heat pump with central, decentralized, or controlled mechanical ventilation (we are still considering these options as well).
1.) Would you remove the battery and replace it with more photovoltaic modules? If yes, how much kWp capacity would you recommend for a single-family home built to KfW 40/55 standard with "normal use," i.e., occasional home office?
2.) Or would you keep the battery and increase the photovoltaic system capacity with additional modules?
Do you have any other ideas or suggestions regarding what we should pay attention to in connection with the photovoltaic system?
You should definitely familiarize yourself with the upcoming policies regarding photovoltaic systems. Starting in 2025, there will no longer be a fixed feed-in tariff; instead, electricity prices from the market will apply. This means that during the morning and midday hours, when the sun is strongest, you won’t get paid for the electricity you feed in. In the evening, when you use the electricity yourself, you would actually earn more for it. These changes will be introduced gradually from 2025. Currently, it’s still unclear up to what system size these regulations will apply (my latest information).
So, take a look at your potential electricity consumers. Do you have a heat pump? Is there an electric vehicle present or planned? If yes, will it be charged at home during midday?
If you don’t have enough consumption, I would recommend getting a small battery storage system. They are quite affordable at the moment.
That way, you don’t have to give away electricity for free at midday.
A modern house usually has a standby power demand of around 300 watts. When cooking or doing laundry, consumption quickly rises to about 5,000 watts. An electric car typically draws around 11,000 watts (11kW).
Filling your roof completely with solar panels should be done cautiously in light of the planned policies, depending on the amount of consumption. Otherwise, you might end up with a full system and be effectively giving away electricity around midday. But some people are altruistic enough to do that willingly.
So, take a look at your potential electricity consumers. Do you have a heat pump? Is there an electric vehicle present or planned? If yes, will it be charged at home during midday?
If you don’t have enough consumption, I would recommend getting a small battery storage system. They are quite affordable at the moment.
That way, you don’t have to give away electricity for free at midday.
A modern house usually has a standby power demand of around 300 watts. When cooking or doing laundry, consumption quickly rises to about 5,000 watts. An electric car typically draws around 11,000 watts (11kW).
Filling your roof completely with solar panels should be done cautiously in light of the planned policies, depending on the amount of consumption. Otherwise, you might end up with a full system and be effectively giving away electricity around midday. But some people are altruistic enough to do that willingly.
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Buchsbaum0669 Sep 2024 14:52rick2018 schrieb:
If I had space (where it wouldn’t bother me visually), I would immediately add another 50 kWp or so.If only.
First, you need approval from the grid operator for the additional 50 kWp. That’s not so easy anymore. Unfortunately, the electrical grids in Germany are quite outdated.
And if you want to expand later, you basically have to start over. Data cables, smart meters, upgrading the meter cabinet, installing storage, and also a new inverter. Filling up the roof just doesn’t make sense.
It only really pays off for large systems with direct marketing.
Buchsbaum066 schrieb:
If only, if only, bicycle chain.
You first need to get approval from the grid operator for the 50 kWp system. That’s becoming quite difficult nowadays. Unfortunately, the electricity grids in Germany are outdated.
And if you want to retrofit later, you start all over again. Data cables, smart meter, modifying the meter cabinet, installing storage, and also a new inverter. Filling the roof simply doesn’t make sense.
It only really pays off for large systems with direct marketing. Yes and no. Fully covering the roof can make sense if there are enough consumers in the household. In winter, you’ll be grateful for every watt. Charging the car directly is probably out of the question. In summer, you’ll appreciate the charged electric car. But as mentioned, it really depends on your specific usage profile. Can the car be charged regularly around midday? Do you have a heat pump? What kind of constant power demand does the garden have (pool pump, garden pump, pond pump, etc.)? Are you working from home? Do you often cook during midday? Do you have programmable washing machines and dryers and are you willing to use that feature?
When we say "full roof," we usually mean 10–18 kWp systems. Those are still manageable sizes. Most people only reach over 20 kWp by including garage and shed roofs. Beyond that, there are only a few who have really large houses with free roof space.
The elderly person who does laundry once a week and whose biggest consumer is the stove/oven certainly doesn’t need a fully covered roof. A balcony solar system is probably enough in that case.
I find myself facing a similar decision regarding the retrofit of a photovoltaic system.
I am also trying to decide between a system with storage, a system without storage, or simply installing a small balcony solar unit on the garage for simplicity’s sake.
If you read various photovoltaic forums, many experienced users recommend fully covering the roof with panels and advise strongly against installing a "pointless" battery.
If I calculate my potential system without storage, the cost of electricity generation over 20 years is about 7 cents per kWh (without financing costs). This is roughly covered by the feed-in tariff, so it only really becomes profitable through self-consumption. When including financing costs, every kWh generated but not used directly at home initially results in a loss.
Therefore, I am unsure whether this forum opinion still holds firmly, as it may stem from earlier times when feed-in tariffs were higher.
Additionally, this calculation only reflects today’s prices. If you factor in a price increase (which, in my view, will occur at some scale), the balance naturally shifts in favor of higher self-consumption compared to a system without storage, and this can only be achieved with a battery system.
Current situation for me:
My heat pump unfortunately cannot be controlled. At the moment, I have one hybrid vehicle and one conventional combustion engine car. However, over the next 20 years, electricity demand is likely to increase due to more electric vehicles.
I have to admit that, despite working with numbers every day, I find it difficult to evaluate all the variables (share of self-consumption, future demand, price increases, battery lifespan, and others) and struggle to make a decision. Depending on which variable I adjust, I get completely different results. Then I think we could just install a small balcony solar unit on the garage to reduce the basic electricity demand, and that definitely pays off in a very short time. But then the “green” conscience kicks in again...
What I have not yet considered is price-based charging of the battery/car in combination with variable electricity tariffs.
I am also trying to decide between a system with storage, a system without storage, or simply installing a small balcony solar unit on the garage for simplicity’s sake.
If you read various photovoltaic forums, many experienced users recommend fully covering the roof with panels and advise strongly against installing a "pointless" battery.
If I calculate my potential system without storage, the cost of electricity generation over 20 years is about 7 cents per kWh (without financing costs). This is roughly covered by the feed-in tariff, so it only really becomes profitable through self-consumption. When including financing costs, every kWh generated but not used directly at home initially results in a loss.
Therefore, I am unsure whether this forum opinion still holds firmly, as it may stem from earlier times when feed-in tariffs were higher.
Additionally, this calculation only reflects today’s prices. If you factor in a price increase (which, in my view, will occur at some scale), the balance naturally shifts in favor of higher self-consumption compared to a system without storage, and this can only be achieved with a battery system.
Current situation for me:
My heat pump unfortunately cannot be controlled. At the moment, I have one hybrid vehicle and one conventional combustion engine car. However, over the next 20 years, electricity demand is likely to increase due to more electric vehicles.
I have to admit that, despite working with numbers every day, I find it difficult to evaluate all the variables (share of self-consumption, future demand, price increases, battery lifespan, and others) and struggle to make a decision. Depending on which variable I adjust, I get completely different results. Then I think we could just install a small balcony solar unit on the garage to reduce the basic electricity demand, and that definitely pays off in a very short time. But then the “green” conscience kicks in again...
What I have not yet considered is price-based charging of the battery/car in combination with variable electricity tariffs.
N
nordanney11 Sep 2024 10:01Musketier schrieb:
If I calculate my "potential" system without a battery, the electricity production costs me about 7 cents per kWh over 20 years (excluding financing costs). This is just about covered by the feed-in tariff, so it only really pays off through self-consumption. Then simply calculate with 20-25% self-consumption. What result do you get?
Regarding the battery:
Just assume 4,000 charge cycles over 20 years (which means for a 10 kWh battery 2,000 kWh per year or 40,000 kWh over 20 years).
Saved electricity cost at the current rate of 25 cents per kWh = €10,000
Lost feed-in tariff at 8 cents per kWh = €3,200
Profit = €6,800 (without price increases)
Can you buy and finance the battery for this amount over 20 years? Will it fail once in 20 years? Can you achieve 40-45% self-consumption (especially in winter you almost never fully charge the battery, and in summer it doesn’t empty completely), or do you cannibalize your existing self-consumption without the battery? Battery losses / efficiency are also not included yet.
Or calculate the other way around. If the 10 kWh battery costs €10,000, the cost per stored and reused kWh is X cents ==> in my example with 4,000 charge cycles, that is 25 cents per kWh (!!!). You can also calculate with more cycles, but then expect about 5% losses during charging/discharging.
In the end, it almost always comes down to the fact that the current prices asked by suppliers for batteries make their use uneconomical. If you can buy one cheaply somewhere yourself and/or have someone who installs it unofficially, the situation might change.
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