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?
T
toxicmolotof2 Mar 2017 19:12If a battery is really planned, the inverter must be capable of handling it. So, you either need to buy a new one or take it into account now, which costs about 1,000 euros more.
However, such a battery does not currently make the system significantly more cost-effective. It is mainly for those with environmental concerns.
However, such a battery does not currently make the system significantly more cost-effective. It is mainly for those with environmental concerns.
From 7 kWp (kilowatt peak) and above, you are currently required by law to have a smart meter installed, which means costs of about €100 (approximately $110) per year. Smaller systems are exempt from this. Yes, this will likely be changed at some point, but we are living in a country that highly values existing rights.
That sounds good. A 7 kWp system should cost around €9,100 net (remember, you initially have to pay €10,829 gross, but you get the VAT back – so liquidity is important).
Photovoltaics and a heat pump are a perfect match. The profitability depends heavily on the self-consumption of the generated electricity, and with a heat pump, you have a large consumer in the house. This brings back the advice from toxicmolotow: maybe consider going up to 10 kWp to generate a bit more electricity for the heat pump during winter. That electricity is almost entirely used for self-consumption (a battery would just stand there uncharged/empty – completely unnecessary). For a 10 kWp system, you’ll probably need to spend a bit more, but the price per kWp should be around €1,100 to €1,200 net.
How do you manage to save €7,000 to €10,000 on the basement? Excavation work?
Photovoltaics and a heat pump are a perfect match. The profitability depends heavily on the self-consumption of the generated electricity, and with a heat pump, you have a large consumer in the house. This brings back the advice from toxicmolotow: maybe consider going up to 10 kWp to generate a bit more electricity for the heat pump during winter. That electricity is almost entirely used for self-consumption (a battery would just stand there uncharged/empty – completely unnecessary). For a 10 kWp system, you’ll probably need to spend a bit more, but the price per kWp should be around €1,100 to €1,200 net.
How do you manage to save €7,000 to €10,000 on the basement? Excavation work?
11,000-12,000 euros, at most 13,000 euros. Net, of course. And it should tend more towards the lower price, as certain efforts in execution can be directly saved with new construction. However, don’t be shocked if you see completely different offers. The range is quite extreme in this industry, and often you’re offered things that don’t make any sense at all.
Google mainly provides a lot of advertising and sugar-coated figures.
Google mainly provides a lot of advertising and sugar-coated figures.
T
toxicmolotof2 Mar 2017 21:26I would interpret “Allerwertesten auf Eimer” as rather not optimal.
However, I still maintain that if 10 kWp is possible, then go for it.
The problem is unfortunately that the photovoltaic system doesn’t produce power exactly when you need it for the heat pump. I’ll upload a typical “frost winter image” of a 5.4 kWp photovoltaic system with a 30° tilt facing south-southwest, combined with an 8 kW geothermal heat pump.
There you can see the “problem.”
However, I still maintain that if 10 kWp is possible, then go for it.
The problem is unfortunately that the photovoltaic system doesn’t produce power exactly when you need it for the heat pump. I’ll upload a typical “frost winter image” of a 5.4 kWp photovoltaic system with a 30° tilt facing south-southwest, combined with an 8 kW geothermal heat pump.
There you can see the “problem.”
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