Johannes 9 kW On-Grid project
Posted: Wed Jul 27, 2022 8:03 pm
Will start documenting something that was super popular in Germany until 2012 and is getting popular again now: a full grid export solar system that you get a fixed feed in tariff for. It's not very exciting but super common. I inquired at an engineering company to plan and build the system for me but they had no free capacity until summer 2023. So I'll do all myself except roof mounting (because high and steep and wanting to survive). I will document all formalities here as well.
Inverter: SMA Sunny Tripower 8.0 - 1900€ delivered
Mounting rack - 1170€ delivered
Fuse box, cables etc. - 250€
Roof mounting: probably about 3000€
Electrical installation approval: 3100€
Total so far: 13520€
Feed in tariff is 0.134€/kWh and I expect yearly energy production to be around 9000 kWh. So it should pay off in around 12 years.
Prices are without VAT as that is always refunded for PV projects in Germany.
Planning
I took a screen shot off google earth with the roof tilted into the horizontal. Then whacked solar panels in there avoiding shadows. Then found out that I'd assumed the wrong width AFTER ordering the solar panels... So instead of 26 I can only fit 23. Oh well, there is no such thing as redundant solar panels, my dad will buy them off me. Electrical installation
every other mounting profile is connected to an earthing cable. Panels are arranged as one string with an idle voltage around 850V. DC+ and DC- first go to a string box that contains surge protection and two fuses. These boxes are available cheap and pre-built, no need to build your own. Then + and - go into the inverter while the three earthing cables from inverter, roof rack and string box are collected at a common star point in the fuse box.
The inverter output runs via 3 regular fuses (because it is 3-phase) and through a bespoke energy meter into the grid. Will update that after talking to the electrician. Cables run completely vertical all the way from the roof, through an existing cable duct, to the basement where I chose to install the inverter. Then AC cable runs back up to the house connection box. Very fun to fiddle 5x2.5mm² cable through some unknown, bendy cable duct. Old trick, first I put the flexible grounding cable in, glued the AC cable to it with some strong tape and pulled it all down.
Legalities
First you need to enquire with your municipal utility whether you there is enough capacity for another solar system. Then I chose to do most of the electrical installation myself and have an electrician do the finishing touch. He will then sign it off and instruct the utility which meter to install in which place. That is being send off and at some point they will show up and install the meters.
Before that the system must be registered with the federal network agency (Bundesnetzagentur)
Most utilities will send you a silly feed-in contract which is NOT needed as everything is regulated by federal law.
Solar panels: 23 JA Solar 405W panels, 1.73x1.13m (amazed you get over 400W from the same area that you got 200W from in 2010) - 4100€ deliveredInverter: SMA Sunny Tripower 8.0 - 1900€ delivered
Mounting rack - 1170€ delivered
Fuse box, cables etc. - 250€
Roof mounting: probably about 3000€
Electrical installation approval: 3100€
Total so far: 13520€
Feed in tariff is 0.134€/kWh and I expect yearly energy production to be around 9000 kWh. So it should pay off in around 12 years.
Prices are without VAT as that is always refunded for PV projects in Germany.
Planning
I took a screen shot off google earth with the roof tilted into the horizontal. Then whacked solar panels in there avoiding shadows. Then found out that I'd assumed the wrong width AFTER ordering the solar panels... So instead of 26 I can only fit 23. Oh well, there is no such thing as redundant solar panels, my dad will buy them off me. Electrical installation
every other mounting profile is connected to an earthing cable. Panels are arranged as one string with an idle voltage around 850V. DC+ and DC- first go to a string box that contains surge protection and two fuses. These boxes are available cheap and pre-built, no need to build your own. Then + and - go into the inverter while the three earthing cables from inverter, roof rack and string box are collected at a common star point in the fuse box.
The inverter output runs via 3 regular fuses (because it is 3-phase) and through a bespoke energy meter into the grid. Will update that after talking to the electrician. Cables run completely vertical all the way from the roof, through an existing cable duct, to the basement where I chose to install the inverter. Then AC cable runs back up to the house connection box. Very fun to fiddle 5x2.5mm² cable through some unknown, bendy cable duct. Old trick, first I put the flexible grounding cable in, glued the AC cable to it with some strong tape and pulled it all down.
Legalities
First you need to enquire with your municipal utility whether you there is enough capacity for another solar system. Then I chose to do most of the electrical installation myself and have an electrician do the finishing touch. He will then sign it off and instruct the utility which meter to install in which place. That is being send off and at some point they will show up and install the meters.
Before that the system must be registered with the federal network agency (Bundesnetzagentur)
Most utilities will send you a silly feed-in contract which is NOT needed as everything is regulated by federal law.