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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toxicmolotof8 Mar 2017 08:32Read up on the topic of East/West... it’s very interesting there.
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Cruiseaddict13 Mar 2017 13:37Actually, from a purely financial perspective, a photovoltaic system hardly makes sense anymore. It only really makes sense for a private individual if they do not feed electricity back into the grid, stay below 10 kWp, and achieve a decent level of self-sufficiency. For that, a battery storage system is absolutely necessary.
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toxicmolotof13 Mar 2017 15:16Why wouldn’t it make sense? The feed-in tariff just about covers the investment costs.
However, the battery drives the levelized cost of electricity up enormously.
However, the battery drives the levelized cost of electricity up enormously.
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Knallkörper13 Mar 2017 16:44toxicmolotow schrieb:
Why wouldn’t it make sense? The feed-in tariff just about covers the investment costs.Actually, you already answer the question in the next sentence. Financially, it probably doesn’t make sense at the moment. The system might pay for itself through the feed-in tariff, but only if repair costs are not taken into account. On the plus side, there are also gains from self-consumption. On the other hand, there are several disadvantages that are harder to quantify objectively and which everyone values differently: appearance of the system – disposal issues – resource waste during production – social and ecological conditions in the manufacturing country.
Here are some assumptions regarding self-consumption:
- Typical homeowner is a couple in their mid-30s with two children
- Both parents work full-time during regular daytime hours
- No electric vehicle
- No air conditioning
In our case, it looks like this:
- Cooking during the week happens only occasionally in the evenings
- Laundry and drying are done when the children are asleep
- When laundry is done, it’s usually a large load at once
- On weekends, we’re not home much during the day – either shopping or going on trips, so energy use is again concentrated in the evenings
- The sauna is only used in the evenings
- Lights are turned on only when it’s dark
We have four refrigerators/freezers (I’m a hunter), which in our example are probably the only significant baseline consumption. Otherwise, I tried to roughly estimate what our self-consumption might add up to. I originally wanted to justify installing a battery system financially, but that didn’t work out, and I think most households are similar in this regard.
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toxicmolotof13 Mar 2017 17:52I never claimed that a battery system makes sense. In my view, it doesn’t.
What prevents them from loading the washing machine and dryer in the evening or morning and then running them consecutively at 11 a.m. and 1 p.m. with the pet?
I see it differently. We are also a family of four, and my wife does the household chores in the morning. The children are home from midday, and in summer, the solar power system provides energy until 9 p.m. (21:00). So it is possible if you want to. But if you really get by with 2000 kWh per year, I completely agree with you.
What prevents them from loading the washing machine and dryer in the evening or morning and then running them consecutively at 11 a.m. and 1 p.m. with the pet?
I see it differently. We are also a family of four, and my wife does the household chores in the morning. The children are home from midday, and in summer, the solar power system provides energy until 9 p.m. (21:00). So it is possible if you want to. But if you really get by with 2000 kWh per year, I completely agree with you.
@ Knallkörper: Well, there are also "atypical" homeowners:
- Couple in their mid-50s, children have moved out
- Both no longer working
- Electric hybrid car present
- Heat pump with cooling function installed
This way, quite a lot of the photovoltaic output is used directly... and there’s a small battery as a gadget on top. Gadgets usually never pay off... and there are more pointless gadgets than such a battery!
- Couple in their mid-50s, children have moved out
- Both no longer working
- Electric hybrid car present
- Heat pump with cooling function installed
This way, quite a lot of the photovoltaic output is used directly... and there’s a small battery as a gadget on top. Gadgets usually never pay off... and there are more pointless gadgets than such a battery!
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