DNO requirements
What is DNO permission and when do you need it? The DNO or distribution network operator is the company responsible for distributing electricity from the National Grid to your home or business. In the UK there are 14 different district networks or DNO regions which are owned by six groups. Find out which DNO you are linked to by adding your postcode to the ENA website here.
When installing solar PV or any form of electricity generation to a grid connected property, the local DNO will need to be informed.Depending on the size of the system this can either be done retrospectively, unless prior permission needs to be granted. If prior DNO permission is required for an installation this can take 8 to 12 weeks to be granted and will necessitate the completion of a G99 - A1.1 Application Form.
The size of the PV system is based on the AC inverter rating rather than the peak DC rating of the panels. If the system size is under 16A per phase (3.68kWp for a single phase supply or 11.04kWp for a three phase supply) then the DNO will just need to be notified within 28 days of the system’s commissioning using a G98 form. Prior permission is not required as the addition of such small systems is very unlikely to cause any load issues to the current infrastructure of the local grid.
(Comparing single-phase vs. three-phase power, three-phase power supplies are more efficient. A three-phase power supply can transmit three times as much power as a single-phase power supply, while only needing one additional wire (that is, three wires instead of two).
However, if the solar PV system to be installed is greater than 16A per phase then prior permission will need to be granted. This is because the grid needs to conduct a network study to determine whether the local grid can handle the added load. The grid may state that additional work needs to be done prior to the installation to cope with the extra energy that the system generates. The DNO will work to a worst case scenario and will design and set requirements in line with these, even if incredibly unlikely, to ensure the security of the grid.
DNO permission is also required for any battery system that has backup functionality and that ‘islands’ the property from the grid in the event of a power cut.
Excerpt from the Government website that you can access here:
Determine if you need to notify the DNO before or after installation. Installation contractors must examine the energy device and required connection to determine whether the Distribution Network Operator needs to be informed before or after installation. ENA have produced Distributed Generation and Storage Connection Guides, which includes a flowchart to help establish which forms should be completed and whether they should be submitted before or after installation.
Once the installation contractor has determined whether the connection is ‘connect and notify’ or ‘apply to connect’, they must follow the relevant instructions:
If the connection is ‘connect and notify’ installers can proceed to install the device and submit the relevant Engineering Recommendation (EREC) G98 application form to the DNO within 28 days of installation. The DNO will assess the notification and be in touch if submitted incorrectly.
If energy device is ‘apply to connect’ installers must submit the relevant Engineering Recommendation (EREC) G99 application form (or G100 if export is limited) to the DNO before installing the device to ensure safe and effective operation of the electricity network. The DNO will be in touch within 45 days for low voltage energy devices and 65 days for high voltage energy devices to approve installation or make further contact about appropriate amendments needed.
If battery storage is being implemented with a generation device and falls under ‘apply to connect’ installers can utilise a fast track application process. This involves submitting the G99 Form A1-2 application form for connection of Fully Type Tested Integrated Microgeneration and Storage installations. This must be submitted before installation but reduces the connection time to 10 days or less.
Note: when completing the form, ENA’s Type Test register may provide useful information on the energy device model being registered. If the energy device is not type tested, the DNO may require additional documentation to demonstrate that it complies with EREC G98/G99.
Surplus energy (info taken from the New Scientist 27/1/23)
Too much green power is a growing problem. As electricity grids tilt increasingly towards renewable energy, grid operators are struggling to know what to do with surplus power. In 2020 and 2021, enough renewable power to supply 800,000 homes went to waste in the UK as the supply of green power outstripped demand, according to energy company Drax.
By the end of the decade, new offshore wind farms built in the UK could mean that the supply of low-carbon wind, solar and nuclear power outstrips demand 53% of the time. It isn’t just a UK problem. Around the world, from the US to China, grid operators are grappling with matching fluctuating supplies of green power with customer demand.
There are all sorts of ideas for how to solve this problem. Interconnectors between grids are part of the solution: undersea cables are being built to carry power back and forth between Britain and mainland Europe to help ensure power gets to where it is needed.
Energy storage options, such as batteries or hydrogen, can be used to soak up power during windy nights when demand is low. Electric vehicle batteries are being reimagined as mobile storage devices, able to charge or discharge on demand according to what the grid needs.
But at a time when energy prices are sky high and households are battling a cost-of-living crisis, some are seeing the challenges of surplus green power as an opportunity to help those most in need.
DNO's cover various areas - but not necessarily the areas you would expect.: see map below to identify your DNO.
We are putting together a list of their phone numbers:
Electricity North West - north west of England excluding Merseyside and parts of Cheshire. 0800 1954141
UK Power Networks - South East of England, East of England and London. 0800 029 4285
Western Power Distribution - South West of England, South Wales and Midlands. 0800 096 3080
Northern Powergrid - North East England and Yorkshire regions and the North Lincolnshire area. 0800 011 3332
When installing solar PV or any form of electricity generation to a grid connected property, the local DNO will need to be informed.Depending on the size of the system this can either be done retrospectively, unless prior permission needs to be granted. If prior DNO permission is required for an installation this can take 8 to 12 weeks to be granted and will necessitate the completion of a G99 - A1.1 Application Form.
The size of the PV system is based on the AC inverter rating rather than the peak DC rating of the panels. If the system size is under 16A per phase (3.68kWp for a single phase supply or 11.04kWp for a three phase supply) then the DNO will just need to be notified within 28 days of the system’s commissioning using a G98 form. Prior permission is not required as the addition of such small systems is very unlikely to cause any load issues to the current infrastructure of the local grid.
(Comparing single-phase vs. three-phase power, three-phase power supplies are more efficient. A three-phase power supply can transmit three times as much power as a single-phase power supply, while only needing one additional wire (that is, three wires instead of two).
However, if the solar PV system to be installed is greater than 16A per phase then prior permission will need to be granted. This is because the grid needs to conduct a network study to determine whether the local grid can handle the added load. The grid may state that additional work needs to be done prior to the installation to cope with the extra energy that the system generates. The DNO will work to a worst case scenario and will design and set requirements in line with these, even if incredibly unlikely, to ensure the security of the grid.
DNO permission is also required for any battery system that has backup functionality and that ‘islands’ the property from the grid in the event of a power cut.
Excerpt from the Government website that you can access here:
Determine if you need to notify the DNO before or after installation. Installation contractors must examine the energy device and required connection to determine whether the Distribution Network Operator needs to be informed before or after installation. ENA have produced Distributed Generation and Storage Connection Guides, which includes a flowchart to help establish which forms should be completed and whether they should be submitted before or after installation.
Once the installation contractor has determined whether the connection is ‘connect and notify’ or ‘apply to connect’, they must follow the relevant instructions:
If the connection is ‘connect and notify’ installers can proceed to install the device and submit the relevant Engineering Recommendation (EREC) G98 application form to the DNO within 28 days of installation. The DNO will assess the notification and be in touch if submitted incorrectly.
If energy device is ‘apply to connect’ installers must submit the relevant Engineering Recommendation (EREC) G99 application form (or G100 if export is limited) to the DNO before installing the device to ensure safe and effective operation of the electricity network. The DNO will be in touch within 45 days for low voltage energy devices and 65 days for high voltage energy devices to approve installation or make further contact about appropriate amendments needed.
If battery storage is being implemented with a generation device and falls under ‘apply to connect’ installers can utilise a fast track application process. This involves submitting the G99 Form A1-2 application form for connection of Fully Type Tested Integrated Microgeneration and Storage installations. This must be submitted before installation but reduces the connection time to 10 days or less.
Note: when completing the form, ENA’s Type Test register may provide useful information on the energy device model being registered. If the energy device is not type tested, the DNO may require additional documentation to demonstrate that it complies with EREC G98/G99.
Surplus energy (info taken from the New Scientist 27/1/23)
Too much green power is a growing problem. As electricity grids tilt increasingly towards renewable energy, grid operators are struggling to know what to do with surplus power. In 2020 and 2021, enough renewable power to supply 800,000 homes went to waste in the UK as the supply of green power outstripped demand, according to energy company Drax.
By the end of the decade, new offshore wind farms built in the UK could mean that the supply of low-carbon wind, solar and nuclear power outstrips demand 53% of the time. It isn’t just a UK problem. Around the world, from the US to China, grid operators are grappling with matching fluctuating supplies of green power with customer demand.
There are all sorts of ideas for how to solve this problem. Interconnectors between grids are part of the solution: undersea cables are being built to carry power back and forth between Britain and mainland Europe to help ensure power gets to where it is needed.
Energy storage options, such as batteries or hydrogen, can be used to soak up power during windy nights when demand is low. Electric vehicle batteries are being reimagined as mobile storage devices, able to charge or discharge on demand according to what the grid needs.
But at a time when energy prices are sky high and households are battling a cost-of-living crisis, some are seeing the challenges of surplus green power as an opportunity to help those most in need.
DNO's cover various areas - but not necessarily the areas you would expect.: see map below to identify your DNO.
- Electricity North West Limited.
- Northern Powergrid. Northern Powergrid (Northeast) Limited. ...
- Scottish and Southern Energy. Scottish Hydro Electric Power Distribution plc.
- ScottishPower Energy Networks. SP Distribution Ltd.
- UK Power Networks.
- Western Power Distribution.
We are putting together a list of their phone numbers:
Electricity North West - north west of England excluding Merseyside and parts of Cheshire. 0800 1954141
UK Power Networks - South East of England, East of England and London. 0800 029 4285
Western Power Distribution - South West of England, South Wales and Midlands. 0800 096 3080
Northern Powergrid - North East England and Yorkshire regions and the North Lincolnshire area. 0800 011 3332