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Bierwächter2 Jun 2025 20:02Hi,
my photovoltaic system planning is likely going to end up at around 38 kWp (kilowatt-peak). The pitched roof will be fully covered on the south and north sides.
My main concern is that I was told (in the relevant forum) that the inverters get quite warm and that I shouldn’t install them in the utility room. We don’t have a basement, and our utility room is about 8.3 m² (90 sq ft). It will be a KfW 40 energy-efficient house. The garage is on the opposite side of the property and is planned to be built later, not directly connected to the house. A carport is planned directly adjacent to the utility room. Currently, I would probably try to install the inverters there. We will have two inverters because of the system size and string configuration. However, our house manufacturer uses a very light plaster, and the inverters are too heavy to mount directly on it. So I would need to mention this during the final selections and have wooden beams installed under the plaster, which would be expensive. Alternatively, I could somehow mount them on the carport itself, but I don’t want to significantly reduce the driveway width since it’s already quite narrow. I could also take the risk and install the inverters in the utility room after all. However, I have heard of cases where temperatures of 40°C (104°F) were reached there. Some people use fans to get rid of the heat. In our KfW 40 house, that probably wouldn’t even be allowed.
I can hardly find any information about this online. Some people report no problems even with 2 m² (22 sq ft) utility rooms; others have temperatures around 30°C (86°F). There is never information about the type of houses, and some posts are up to 10 years old. We are building a 103 m² (1,109 sq ft) bungalow for two people, with an Alpha Innotec Hybrox 5 (70 m² to 150 m²) air-to-water heat pump and a decentralized ventilation system.
Has anyone here had experience with inverter heat? How would you approach this issue? The battery storage obviously has to go in the utility room; it can’t be installed elsewhere.
my photovoltaic system planning is likely going to end up at around 38 kWp (kilowatt-peak). The pitched roof will be fully covered on the south and north sides.
My main concern is that I was told (in the relevant forum) that the inverters get quite warm and that I shouldn’t install them in the utility room. We don’t have a basement, and our utility room is about 8.3 m² (90 sq ft). It will be a KfW 40 energy-efficient house. The garage is on the opposite side of the property and is planned to be built later, not directly connected to the house. A carport is planned directly adjacent to the utility room. Currently, I would probably try to install the inverters there. We will have two inverters because of the system size and string configuration. However, our house manufacturer uses a very light plaster, and the inverters are too heavy to mount directly on it. So I would need to mention this during the final selections and have wooden beams installed under the plaster, which would be expensive. Alternatively, I could somehow mount them on the carport itself, but I don’t want to significantly reduce the driveway width since it’s already quite narrow. I could also take the risk and install the inverters in the utility room after all. However, I have heard of cases where temperatures of 40°C (104°F) were reached there. Some people use fans to get rid of the heat. In our KfW 40 house, that probably wouldn’t even be allowed.
I can hardly find any information about this online. Some people report no problems even with 2 m² (22 sq ft) utility rooms; others have temperatures around 30°C (86°F). There is never information about the type of houses, and some posts are up to 10 years old. We are building a 103 m² (1,109 sq ft) bungalow for two people, with an Alpha Innotec Hybrox 5 (70 m² to 150 m²) air-to-water heat pump and a decentralized ventilation system.
Has anyone here had experience with inverter heat? How would you approach this issue? The battery storage obviously has to go in the utility room; it can’t be installed elsewhere.
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nordanney2 Jun 2025 20:23What temperature do the inverters generate? That should be specified in the datasheets.
You can calculate it yourself. How much electricity do you produce per day? What is the inverter’s efficiency? The rest is waste heat distributed throughout the day. If you are clever, you could use a hot water heat pump that cools the room in the process.
Based on the size of the system, the electricity produced, and the conditions, I would intuitively expect the room to get quite warm and seriously consider installing the inverters outside.
You can calculate it yourself. How much electricity do you produce per day? What is the inverter’s efficiency? The rest is waste heat distributed throughout the day. If you are clever, you could use a hot water heat pump that cools the room in the process.
Based on the size of the system, the electricity produced, and the conditions, I would intuitively expect the room to get quite warm and seriously consider installing the inverters outside.
Bierwächter schrieb:... because no more than one inverter for 5kWp is installed and the technical room is in an older building.
Some don’t have problems even with 2sqm (square meters) technical rooms
Bierwächter schrieb:I don’t think it will stay that cool in your case.
others have around 30 degrees.
Hello,
although I am a fan of "maximizing roof space," I still consider 38 kWp a clear overkill. If you can get it for well under $1,000 per kWp, okay. But otherwise!?
Regarding your question: yes, inverters generate waste heat, and quite a bit at that. Expect about 2-3% power loss, so roughly 1–1.5 kW of heat output. Your technical room will indeed turn into a sauna. I have even heard of people installing air conditioning because of this!
The carport is actually a very good location, but you need to make sure that the inverters will not be flooded during heavy rain. And about the clearance for driving through: could you install them at 2 m (6.6 ft) height? That way, they wouldn’t restrict your driving width.
Best regards,
Andreas
although I am a fan of "maximizing roof space," I still consider 38 kWp a clear overkill. If you can get it for well under $1,000 per kWp, okay. But otherwise!?
Regarding your question: yes, inverters generate waste heat, and quite a bit at that. Expect about 2-3% power loss, so roughly 1–1.5 kW of heat output. Your technical room will indeed turn into a sauna. I have even heard of people installing air conditioning because of this!
The carport is actually a very good location, but you need to make sure that the inverters will not be flooded during heavy rain. And about the clearance for driving through: could you install them at 2 m (6.6 ft) height? That way, they wouldn’t restrict your driving width.
Best regards,
Andreas
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nordanney2 Jun 2025 20:29andimann schrieb:
Hi,
even though I am a fan of "filling the entire roof," I still think 38 kWp is definitely overkill. Why? You could even set up two separate systems with different purposes. One for full feed-in and one for self-consumption. Especially at this size, the system becomes very cheap when calculated per kWp.
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Bierwächter2 Jun 2025 20:40The system will be installed independently. I think I can manage to keep everything under €20,000 (about $22,000). High-quality panels, mounting materials, storage, inverters, and the electrician for the inspection.
Here’s a small picture because it looks so appetizing.
The roof will be dark gray/black. Fully black Aiko Neostar 3s+ panels are planned. The inverter will probably be a hybrid and a standard one, but this is not finalized yet. Registered for two people, the limits will not be exceeded.
Thanks for your opinions. I definitely plan to install the inverters outside. Whether a conduit to the carport is better or directly mounting them on the beams can probably be decided during the material selection process. The idea of mounting them higher is good; I hadn’t thought of that.
Here’s a small picture because it looks so appetizing.
The roof will be dark gray/black. Fully black Aiko Neostar 3s+ panels are planned. The inverter will probably be a hybrid and a standard one, but this is not finalized yet. Registered for two people, the limits will not be exceeded.
Thanks for your opinions. I definitely plan to install the inverters outside. Whether a conduit to the carport is better or directly mounting them on the beams can probably be decided during the material selection process. The idea of mounting them higher is good; I hadn’t thought of that.
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