The official amperage limit for solar inverters in Ireland is 25 Amps. This works out to 5.75 kW assuming the official Irish voltage of 230 Volts. However, for a long time, you could get permission to install any inverter up to 6 kW, without issue. This is changing, as ESBN are now looking to strictly enforce the 25 A limit.
What about systems that have already been installed?
Previously installed systems up to 6 kW will be fine, as long as the NC6 form was submitted to ESBN, and ESBN did not object to the installation. An NC6 form should have been completed for every solar installation in Ireland.
What about systems that are about to be installed?
There is talk of a grace period until the end of May 2023 for solar inverters up to 6 kW in power, which exceed the 25 Amp limit. So if you’ve already bought a bigger inverter, you should be okay, but be absolutely sure to get NC6 approval before going ahead with the installation.
Why is the 25 A limit only becoming an issue now?
1) Before 2003, Irish grid voltage was 240 Volts. So 6 kW would not in theory be more than 25 Amps. So far so good. But the continent was using 220 Volts. In order to make things standard, we split the difference in 2003 and called it “230 Volts” all round. In practice though, if you stick a multimeter into an Irish socket, you will still probably get 240 Volts. So again in practice, you won’t generally get more 25 Amps off a 6 kW inverter. But in theory you can, as the voltage is “officially” 230 Volts.
2) Presumably, who ever was working at the ESBN before now considered the difference to be within tolerances. An extra amp or two would not have mattered much at the time given there were so few solar PV installations until recent years.
3) Now with tens of thousands of solar panel systems on the way, those extra amps could really start to add up. So ESBN may be forced to enforce the rules more strictly. Alternatively, they might just have someone more pernickety in the office these days.
Can I still have a 6 kW inverter?
Yes, you can still install a 6 kW inverter, provided it has a (hardware or firmware) current limit of no more than 25 amps. In practice, such an inverter will generate the full 6 kW, because in practice the Irish grid voltage is generally 240 Volts. However, using the software settings of an inverter to set a 25 Amp current limit is not enough to satisfy the regulations, because the software setting can easily be changed by users.