Powering Change
Installing since 2010 · 0118 951 4490 · info@spiritenergy.co.uk
Due to the G98 connection limit of 3.68kWp per phase, most residential solar systems on a standard single-phase supply are sized at or around 4kWp. G98 is a straightforward post-installation notification process — for systems within this threshold, prior DNO approval is not required and the installer notifies the DNO on your behalf after commissioning.
While a 4kWp system is appropriate for many UK properties, average annual household electricity consumption is now around 3,500kWh, and many properties, particularly those with electric vehicles, heat pumps, or larger households, consume significantly more.
In an ideal world, a solar PV system should be sized with a similar level of output to household consumption. Battery storage should then be sized with a usable capacity of approximately 1 to 1.5 times the daily PV output.
For example, in the case study below, a property with an electricity consumption of 7,000kWh per annum would benefit from a 6.5kWp PV system producing approximately 6,650kWh per year, combined with 10kWh of battery storage. Overall, the PV and battery storage together would provide approximately 70% of the property's electricity requirement.
Prior DNO permission via a G99 application is required to connect a system to the grid where the inverter rating exceeds 3.68kWp per phase. Unlike G98, G99 requires formal approval before installation can begin, and the DNO has up to 45 working days to respond, though in practice the process can take 8–16 weeks. We handle all DNO applications on your behalf.
With sufficient on-site load, extending an existing system and adding battery storage can make strong financial sense.
If the DNO does not give permission to connect a system of the required size, an export limiter can be installed. The export limiter prevents the system from exporting electricity above the agreed DNO threshold, while still allowing the full array to generate for on-site use and battery charging.
Many homeowners choose to stay within G98 limits by using export limiting, allowing a larger inverter capacity while capping export to 3.68kW. This avoids the G99 pre-approval process while still benefiting from the additional generation for self-consumption and battery charging.
Note that the installation of an export limiter itself still requires DNO notification.
A householder already has 4kWp of solar installed. The system produces 3,800kWh of electricity a year, of which approximately 63% is used on site (2,376kWh). This represents only around a third of the household's 7,000kWh annual electricity usage.
The householder applies to the DNO via a G99 application for permission to connect a further 2.5kWp of solar. Permission is granted, and the additional panels are installed alongside a 10kWh battery storage system to maximise on-site use of the additional generation.
On-site usage of PV generation increases to 78%, with the solar system contributing 4,830kWh to on-site energy usage. Overall, solar now supplies 69% of the property's electricity consumption.
Over a 20-year system life, the batteries are expected to discharge over 38,700kWh of energy.
The household also has an Emergency Power Supply, managed via a secondary consumer unit with designated emergency loads.
Please contact us to find out more about being as self-sufficient as possible and we will tailor a proposal to meet your needs!
