We are becoming a separate company

In April 2019, the Electricity System Operator is becoming a separate company within the National Grid Group. Find out more about what this change will mean.

​Mandatory response services

Mandatory frequency response (MFR) is an automatic change in active power output in response to a frequency change. The service helps us to keep frequency within statutory and operational limits.

Providers can offer one of these or a combination of different response times.

Primary response

Response provided within 10 seconds of an event, which can be sustained for a further 20 seconds.

Secondary response

Response provided within 30 seconds of an event, which can be sustained for a further 30 minutes.

High frequency response

Response provided within 10 seconds of an event, which can be sustained indefinitely.


Providing MFR

Depending on their size and location, a power station may be obliged to have the capability to provide MFR. This requirement will be set out in their connection agreement and is summarised in the table below.

Summary of connection agreement capability for MFR 
 National GridScottish PowerScottish Hydro Electricity Transmission
Small< 50 MW< 30 MW< 10 MW
Medium50 MW =< 100 MWN/AN/A
Large=> 100 MW=> 30 MW=> 10 MW

Offering MFR alongside other balancing services

You may provide other balancing services, as long as doing so does not interfere with your ability to deliver MFR.