Inverter and grid connection
G98 limit check (16 A per phase)
- where
- total generation on the phase (kW)
- PV inverter rated AC output (kW)
- battery or other generator rated output (kW)
- rated output current per phase (A)
- nominal phase voltage (V)
- headroom to the 16 A G98 limit (A)
- G98 limit at this voltage (kW)
Explain this equation
Checks whether the generation on one phase stays within the 16 A per phase limit for connecting under G98 (fit and notify). Use it when adding PV, batteries or both.
Inverter ratings on the same phase add up. Converting kW to watts and dividing by the phase voltage gives the rated current. G98 allows up to 16 A per phase, so the headroom is 16 minus that current. The limit expressed in kW is 16 A times the voltage.
Power equals voltage times current, rearranged for current.
Sense check: at 230 V the limit is 3.68 kW per phase, so a 3.68 kW inverter uses it all. Adding a 3 kW battery inverter takes you over.
Watch out: G98 uses the inverters' rated outputs, not what you expect them to export. Over the limit you need a G99 application or a DNO-approved export limitation scheme.
Checks whether the generation at a single premises stays within the EREC G98 limit of 16 A per phase, so it can be connected first and notified afterwards.
Enter your values to see the result.
Good to know
Add every generator and battery inverter that can export on that phase, using the rated AC output on the inverter datasheet and its G98 type-test certificate. At 230 V, 16 A is 3.68 kW. For a single premises, install and then send the G98 notification to the DNO within 28 days. Several G98 installations close together (within 500 m) must apply before installing.
Common mistake
Using the array kWp, or leaving out an AC-coupled battery inverter, when totalling capacity.
Limits
Single premises, fully type-tested units only. Larger systems or multiple installations follow G99 or the G98 multiple-premises process. Your DNO's published procedure applies.
Sources
- National Grid Electricity Distribution: G98 connection procedures (aggregate registered capacity 16 A (3.68 kW) per phase or less; single premises: install then notify within 28 days; multiple premises within 500 m: apply first)
- ENA Engineering Recommendation G98: Requirements for the connection of fully type tested micro-generators (up to and including 16 A per phase) in parallel with public LV distribution networks
Results are calculations from the published methods and figures shown, and depend on the data you enter. Follow MCS standards, manufacturer data, BS 7671, the ENA connection rules and Building Regulations. System design and DNO applications need a competent, certified installer.