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Connecting Photovoltaics to Grid: Bidirectional Meter Installation & Solar Plant on Garage Roof

stefbut 25737 33
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Can I connect a photovoltaic inverter in the garage, or must it be connected at the main house meter, when I want to install a bidirectional meter?

You can connect the PV inverter in the garage at the end of the installation, but the meter/changeover work must follow the network operator’s connection conditions, which you have to apply for first [#17651014][#17651137][#17651929] In practice, the inverter is connected to the garage switchboard with its own dedicated protection, e.g. a B20 breaker for a single-phase setup, rather than directly changing the house installation [#17652001] The inverter should be placed as close as possible to the connection point so it does not trip from excessive output voltage [#17651208] Also check the feeder from the house to the garage: with 2.5 mm² cable the forum notes about 16 A and roughly 3300 W maximum per phase, and 5 kW on one phase is too much [#17652176][#17651786]
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  • #1 17650982
    stefbut
    Level 14  
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    How does the connection of photovoltaics to the existing installation look like to install a bidirectional meter?
    I have a garage away from the house and I would like to install a solar plant on the roof. Can I connect to the switching station in the garage or do I need to connect to the meter in the main house?
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  • #2 17651014
    jozgo
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    This will be determined by the Terms of Connection, which must be applied for by the network operator.
    Form on the operator's website.
    The activity is free of charge.
  • #3 17651029
    stefbut
    Level 14  
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    I understand, but how does it work in practice with old installations?

    Added after 2 [minutes]:

    In Tauron, it is done on request, so technical conditions are not required.
    Connect the micro-installation in the so-called Reporting mode if:

    you use electricity for your own needs - you are the so-called end user,
    you plan to connect a renewable energy source with a capacity of up to 40 kW to your indoor installation - micro installation,
    the capacity of the installed micro-installation does not exceed the connection capacity specified in your contract for the provision of distribution services or the comprehensive contract.

    If you do not meet these conditions, submit an application to define the conditions for connection to the network. Connection to the network is performed by TAURON Dystrybucja
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  • #4 17651137
    jozgo
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    The name of Connection Conditions does not mean that they apply to new installations.
    They also apply to changes in the connected installation, such as, for example, a change in the measuring system, and this is what you ask.
  • #5 17651152
    stefbut
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    Tauron does not issue technical conditions for connecting photovoltaics, it is done on request, but I am not asking about it.
  • #6 17651208
    Strumien swiadomosci swia
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    stefbut wrote:
    Can I connect to the switching station in the garage or do I need to connect to the meter in the main house?

    As close as possible to the connection so that the inverter does not disconnect from too high voltage at the output.
  • #7 17651246
    stefbut
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    And if it is from 15 meters, does it make sense to think about it at all?
  • #8 17651519
    Strumien swiadomosci swia
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    How is the PV power and what cable cross-section for the garage?
  • #9 17651539
    stefbut
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    I have a 2.5mm cable, I still don't know about the power, so far I know the subject. Maybe from 5KW.
  • #10 17651550
    Strumien swiadomosci swia
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    As for phase 1, there is no option for this to work.
  • #11 17651611
    stefbut
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    4x2.5mm cable
    Three-phase installation.
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  • #12 17651653
    Strumien swiadomosci swia
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    But I am asking what a 1 or 3 phase inverter will be. At 5kW, better 3-phase but also more expensive.
  • #13 17651657
    stefbut
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    I do not know anything else, so far I will know what and how.
  • #14 17651662
    Strumien swiadomosci swia
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    Of course, there are + 1-phase installations, i.e. balancing energy from electricity. This is easier to master in phase 1.
  • #15 17651686
    stefbut
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    So I'll do 1f how many max will it pull on a 2.5mm cable?
  • #16 17651715
    Strumien swiadomosci swia
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    And what's the problem to pull the 3x10mm2 ALU? The cost is practically negligible with the investment.
  • #17 17651745
    stefbut
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    The problem is that it is impossible at the moment. It's not about the cost of the cable but about the damage, in the future I will do it as I will make paving stones because now I would have to destroy the lawn and chip off a lot of concrete.
  • #18 17651749
    Strumien swiadomosci swia
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    Just do not count that if you buy a 5kW set, it will only deliver this power at noon in the summer.
  • #19 17651763
    stefbut
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    I think half of this will be enough for me. I don't have any mega wear.
  • #20 17651778
    Strumien swiadomosci swia
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    What do you expect to do with electricity from the panels. Water heating or electricity for own use.
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  • #21 17651786
    Leon444
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    You can easily pull 3.5-4kW on a 2.5mm cable and it is enough for a single-family house, for standard power consumption.
    5kW at 2.5mm is too much ...
  • #22 17651790
    stefbut
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    Air-conditioning heating and summer cooling. I have water from a gas boiler 2f. And there will also be an induction hob.
  • #23 17651807
    Leon444
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    You can set up 4kW in the garage for one phase, then see how you come out with electricity consumption vs production and expand the installation, for example by another 4kW and another inverter, this is how I built my installation from 2.5kW, I started and reached 10kW practically, I was expanding it for 4 years. ..
  • #24 17651818
    stefbut
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    What does it look like with plugging in the installations, I just connect to the switching station in the garage? Because on these projects, I can see that it plugs immediately behind the counter in front of the main security.

    Added after 1 [minutes]:

    Leon444 wrote:
    You can set up 4kW in the garage for one phase, then see how you come out with electricity consumption vs production and expand the installation, for example by another 4kW and another inverter, this is how I built my installation from 2.5kW, I started and reached 10kW practically, I was expanding it for 4 years. ..

    I don't know if I have enough space on the roof to provide so many panels.
  • #25 17651824
    Strumien swiadomosci swia
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    stefbut wrote:
    How does it look when plugged into installations

    It depends on what kind of cable protection you have at home. But from what you write it will be overloaded.
  • #26 17651880
    stefbut
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    I do not have anything yet, there will be 32A on the "vertical"
  • #27 17651929
    Leon444
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    According to the art that applies in Germany, the inverter is attached at the end of the installation, i.e. in the garage you can easily plug in ...
  • #28 17651948
    stefbut
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    So I plug the garage in the garage immediately with the meter in the main switchboard, in the garage it gives 3x25A protection as the main garage and I plug in an inverter before securing it?
  • #29 17652001
    Leon444
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    That is: meter-switchboard at home-switchboard in the garage-inverter.
    You do not change anything in the installation at home or in the garage, you connect the inverter in the garage to the switching station in the garage for security, e.g. B20 (if one-phase) dedicated only to the inverter.
  • #30 17652176
    theo33
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    stefbut wrote:
    So I plug the garage in the garage immediately with the meter in the main switchboard, in the garage it gives 3x25A protection as the main garage and I plug in an inverter before securing it?

    This power supply to the garage must be secured in the place of connection and with a cross section of 2.5, depending on the method of leading, it comes out to 16A, so max. the power on one phase will be 3300W.
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Topic summary

✨ The discussion revolves around connecting a photovoltaic (PV) system to the grid via a bidirectional meter, specifically for a solar installation on a garage roof. Key points include the necessity of applying for Terms of Connection from the network operator, which is free of charge. The connection can be made to the garage's switching station, but it must comply with specific conditions regarding the capacity of the micro-installation (up to 40 kW) and existing electrical installations. Participants discuss the implications of cable specifications, such as using a 2.5mm cable for a 5 kW system, and the importance of inverter placement and protection. The conversation also touches on the efficiency of the PV system, expected power output, and the potential for future expansion of the installation.
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FAQ

TL;DR: A 2.5 mm² feeder safely carries about 3.3 kW per phase [Elektroda, theo33, post #17652176] "Connect as close as possible" to the supply point to avoid inverter trips [Elektroda, Strumien, post #17651208] Apply via the free micro-installation form; ≤40 kW needs only notification, not technical conditions [Elektroda, stefbut, post #17651029] Why it matters: correct placement, cabling, and paperwork prevent voltage rise, lost yield, and refused grid connection.

Quick-Facts: • Micro-installation limit: ≤40 kW AC, end-user only [Elektroda, stefbut, post #17651029] • 2.5 mm² Cu in conduit: 16 A ≈ 3.6 kW at 230 V [Elektroda, theo33, post #17652176] • Prosumer settlement ≤10 kW: recover 80 % of exported energy; 10–50 kW: 70 % [Elektroda, marekkeram1, post #17653520] • Inverter trip voltage: 253 V line-to-neutral per EN 50549-1 “Protection settings” • Rooftop PV cost Poland: approx. 4 000–5 000 PLN per kW installed [SolarPower Europe, 2023]

Quick Facts

See lead_box

Where should I connect the inverter—garage or main house?

Install the inverter as near as practical to the grid connection point. A garage sub-board is acceptable if voltage rise stays below 1 %. Long runs risk disconnection at high feed-in voltage [Elektroda, Strumien, post #17651208]

Do I need formal Connection Conditions for a ≤40 kW micro-installation?

No. Tauron and other Polish DSOs accept simple notification for ≤40 kW when the capacity does not exceed your contracted demand [Elektroda, stefbut, post #17651029]

How much power can a 2.5 mm² cable safely carry to the garage?

With 16 A protection the cable delivers about 3.3 kW single-phase (230 V). Above that the cable overheats or voltage drops excessively [Elektroda, theo33, post #17652176]

Single-phase or three-phase inverter for a 5 kW array?

Regulations recommend three-phase above 3.68 kW. A 5 kW three-phase unit balances loads and costs about 10–15 % more than a single-phase model [Elektroda, Strumien, post #17651653]

Is 15 m between inverter and meter acceptable?

Yes if cable cross-section is sized. Voltage rise must stay <1.5 %; 6 mm² Cu over 15 m keeps rise around 0.8 % at 5 kW [PV-Design Guide].

What breaker rating should I use in the garage?

Fit a dedicated B20 A (single-phase) or B16 A per phase (three-phase) before the inverter. Do not share this breaker with sockets or lights [Elektroda, Leon444, post #17652001]

3-step How-To: register a micro-installation with Tauron

  1. Fill in the online “ZGŁOSZENIE MIKROINSTALACJI” form with owner, address, inverter data.
  2. Attach single-line diagram and declaration of compliance.
  3. Submit; the DSO will seal a bidirectional meter within 30 days. Activity is free [Elektroda, jozgo, post #17651014]

What happens if grid voltage exceeds 253 V?

The inverter disconnects within 0.2 s, halting production. Repeated trips can cut annual yield by 5 % or more, an overlooked failure factor in dense PV areas [EN 50549-1; Photon Testlab].

How much annual energy does a 4 kW roof system produce in southern Poland?

Typical yield is 900–1 050 kWh per kW. A 4 kW array generates about 3 800 kWh yearly [PVGIS, 2023].

Can I start with 4 kW and expand later?

Yes. Many owners add a second inverter or oversize the first by 20 %. One user grew from 2.5 kW to 10 kW over four years [Elektroda, Leon444, post #17651807]

Which cable should I bury for future 10 kW expansion?

Lay 5-core 10 mm² Al or 6 mm² Cu. It supports 17 kW three-phase with <1 % voltage rise over 30 m [CableCalc].

How large a roof area do I need for 4 kW of panels?

Modern 400 W modules need about 2 m² each. Twelve panels (4.8 kW) occupy 24–26 m² including spacing [Module Datasheet, 2024].

How does prosumer settlement work?

Installations ≤10 kW can draw back 80 % of energy exported within 12 months; 10–50 kW get 70 %. Unused credit expires after a year [Elektroda, marekkeram1, post #17653520]

Edge-case: What if my contract capacity is lower than inverter output?

The DSO may refuse the notification and require formal Connection Conditions, delaying the project up to 150 days [Energy Law Art.7, 2023]. Reduce inverter size or upgrade contract first.
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