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G99 Connection procedure

Does my installation apply?

This connection procedure applies to generation installations that are either rated above 16A (3.68kW) per phase or that do not meet the requirements of the current version of an Energy Networks Association (ENA) document called Engineering Recommendation G98.

Where this connection procedure applies, the generation and the installation must comply with the current version of ENA Engineering Recommendation G99. 

For more information on connecting generation under the G99 connection procedure, please refer to the Energy Networks Association website.

What should I do?

You should apply using the appropriate G99 application forms. 

Power generating modules with an aggregate capacity >50kW 3 phase or >17kW single phase

The connection application should be made using the Standard Application Form.  As a minimum, parts 1-3 should be completed at application stage.  Parts 4 and 5 shall be completed where the information is available and, in any case, should be submitted prior to the connection being made. 

Power generating modules with an aggregate capacity ≤50kW 3 phase or ≤17kW single phase

Where the power generating module is fully type tested and registered in the ENA Type Test Verification Report Register, application form A1-1 should be completed.

Where the power generating module is not type tested or only part type tested, application form A1-1 should be completed and submitted along with one of the following forms (as appropriate): 

  • A2-1 Compliance verification report – tests for Type A synchronous power generating modules up to and including 50kW – test record
  • A2-2 Compliance verification report for synchronous power generating modules >50kW and also for synchronous power generating modules ≤50kW where the approach of this form is preferred to that in Form A2-1
  • A2-3 Compliance Verification Report for inverter connected power generating modules 

Copies of all relevant forms are available here.

For information relating to the implementation of the EU Network Codes, including the transition from G83 to G98, please click here.

Witness testing

Engineering Recommendation G99 sets out the requirements for commissioning tests and checks. It is the responsibility of the installer to undertake these tests and ensure the generation units meet all the relevant requirements.

In some instances, we may need to witness the testing which will incur a fee. For further information regarding our fees please click here. We will notify you in advance should a witness test be required.

What happens next?

Once you are confident that you wish to proceed, please complete and submit an application form. The following flowchart identifies what will happen once we receive your application form.

Once we have received your application we will check to see if your proposed generation can be connected to our existing network without additional work. If we do need to strengthen our network or if you need a new electricity connection we will give you an estimate for carrying this out. If you would like information on our connection charges please click here.

Once we have agreed all the details with you and we have carried out any necessary work on our network, you may go ahead and commission your generation.


We will include within the Connection Offer a series of milestones that the customer must meet or risk losing their Offer. The milestones set prescribed periods that take effect from the acceptance date of the Connection Offer and indicate certain key stages in the scheme’s development that the customer must meet. The milestones provide a mechanism under which we can monitor the progress of a scheme and, if any milestone is missed (or likely to be missed) we can liaise with the customer and discuss progress with them.

For more information on the background to the introduction of milestones, the typical milestones and timescales included within a Connection Offer and how these are managed by WPD, please see our guidance on Extension of validity acceptance.

Useful Information

Types of connection offer available

Electricity connection offer expenses regulations

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