Guidance

Specified generator: when you need a permit

Find out if and by when you need to apply for a specified generator environmental permit to meet air quality requirements.

A generator is a combustion plant that generates electricity, including:

  • engines
  • gas turbines
  • boilers – that operate as a combined heat and power combustion plant

A direct drive and heat only combustion plant is not classed as a generator. But it’s still a medium combustion plant (MCP).

Definition of a specified generator

The term ‘specified generator’ covers an individual generator or a number of generators if they’re:

  • on the same site
  • operated by the same operator
  • for the same purpose (generating electricity)

Generators are still classed as operating for the same purpose if they’re:

  • using different fuels or technologies
  • under contract for a capacity marketing agreement or to provide a balancing service

If you have more than one generator on your site you’ll need to aggregate your generators into a specified generator. You’ll need one permit for the site.

Use this guidance to work out:

  • if your generator is excluded from specified generator controls
  • the specified generator’s capacity
  • whether the specified generator qualifies for transitional arrangements
  • the deadline for applying for the environmental permit
  • how to aggregate your generators into a specified generator

Generators affected by Medium Combustion Plant Directive (MCPD) controls

Both the MCPD and specified generator regulations can apply to generators.

If your site includes a medium combustion plant that generates electricity you must check if your generator:

  • is excluded from both specified generator and MCPD controls – if it’s excluded from one but not the other you’ll still need to apply for a permit
  • is required to meet both specified generator and MCPD controls – you’ll need to apply for the environmental permit with the stricter controls and earlier deadline
  • is already permitted under the Environmental Permitting Regulations but must also meet MCPD requirements

Check using the guidance on Medium combustion plant: when you need a permit.

Excluded generators

These generators are excluded from specified generator controls. For a MCP that generates electricity you must also check if the MCP is excluded from the MCPD controls.

Chapter 2 or 3 Industrial Emissions Directive (IED) installation

Generators that are part of an IED installation under chapter 2 or 3 are excluded.

However, the regulators will use the MCPD and specified generator requirements to inform the site-specific best available techniques. These are the minimum standards they will apply. See how to meet MCPD and specified generator requirements for IED chapter 2 installations.

Nuclear safety role

Generators that have a defined nuclear safety role under a nuclear site licence issued by the Office for Nuclear Regulation are excluded.

Emergency backup generators

From 1 January 2019, a backup generator only used to provide power at a site during an emergency is excluded. However, it is a MCP and requires a permit by the appropriate deadline.

Using a backup generator for the following is not classed as emergency use:

  • providing a balancing service (whether procured or not)
  • demand side response operations such as triad avoidance or fast frequency response

For an on-site emergency, there’s no restriction on the total number of hours:

  • a backup generator can operate for – operators must try to reduce the period and frequency of emergency use
  • ‘black start’ backup generators can operate for

Number of hours you can test backup generators

You must not carry out more than 50 hours testing a year for each backup generator. You must get agreement in writing from your regulator if you want to increase this limit. The regulator can exclude commissioning time within the written agreement.

For each backup generator, you must record the number of hours you test during the year. This is to demonstrate that you meet the exclusion criteria.

If you exceed the limit of 50 hours testing a year without written agreement the regulator will take appropriate enforcement action.

Data centres

Data centres that use an on-site emergency backup generator when the transmission frequency is unstable are excluded. This is provided the generator is not part of a formal agreement or contract.

How to test backup engines

When you test backup engines you should:

  • stagger the tests if you have multiple backup engines
  • keep testing times and frequency to the minimum – just enough to demonstrate reliability at the appropriate load
  • only test when you expect low ambient nitrogen oxides (NOx) background, such as not during peak traffic periods
  • use the electricity generated from the test on your site
  • install backup generators away from sensitive receptors (not below windows or venting onto car parks) and terminate the exhaust flues vertically, making sure there are no obstructions

Offshore generators

Generators operated offshore are excluded.

Gas storage and unloading platforms

Generators installed on a gas storage or unloading platform are excluded.

Research and development testing

For the requirement in England see the Environment Agency’s Regulatory Position Statement Operating a schedule 25B, Tranche B specified generator for research and development: RPS 220.

Mobile generators

The owner of the mobile generator is responsible for its compliance with specified generator controls.

Specified generator controls do not apply to a mobile generator that is designed to move or be moved (on roads or land). However, the controls do apply if it:

  • generates electricity for the national transmission or distribution system to cover a specified generator that’s out of operation
  • performs a function that a static generator could do

The regulator will decide whether a mobile generator is operating as a static generator. They will look at:

  • the nature of the activity the operator’s doing and other equipment they’re using
  • whether the site is relatively permanent or transient
  • how long the generator is in a single location – if it’s in place for 6 months or more the regulator will consider it to be functioning like a static generator and the controls apply
  • whether the site is finished or parts of it are under construction

Mobile generators used for planned maintenance or emergencies

Specified generator controls do not apply when the mobile generator is used for planned maintenance or emergencies. These are examples of maintenance or emergency use from different sectors:

  • water utilities – emergency use or when replacing assets such as pumps and electrical infrastructure
  • IT and telecoms – routine maintenance activities of data centres or telecom switch sites
  • general building maintenance activities such as low voltage and high voltage switchgear upgrades and replacements
  • running electricity transmission and distribution during an emergency or planned maintenance

Mobile generators on construction sites

Specified generator controls do not apply to a mobile generator used on a construction site.

However, if only part of a site is under construction, the regulator will assess whether a mobile generator is performing a function that a static generator could do.

Capacity

Specified generator controls, unless excluded, apply to generators with a rated thermal input between 1MWth and 50MWth.

They also apply to generators less than 1MWth, if they:

  • have a capacity agreement or an agreement to provide a balancing service
  • are part of a specified generator group which in total has a rated thermal input of between 1MWth and less than 50MWth

Rated thermal input is the capacity of the specified generator. It’s calculated using the net calorific value (CV) not the gross CV.

You can ask the manufacturer for this value or you can calculate it using Association of Manufacturers of Power generating Systems (AMPS) method.

More time to comply – who qualifies

Some operators have more time to get their permit in place and comply with permit conditions (this is called a transitional arrangement).

You can use the transitional arrangement if one of the following applies:

  • your generator was already operating before 1 December 2016
  • you already had a contract to provide services to the national grid (capacity agreement, balancing service contract or feed-in tariff (FIT) accredited application) before 31 October 2017

The regulators consider that a capacity contract is the same as a capacity agreement.

These are called ‘Tranche A’ generators.

Contracts made after 31 October 2017 can only get Tranche A status if the generator stopped generating for the contract and it ended before 31 December 2018.

Participating in triad avoidance does not affect Tranche A status.

Those that do not qualify are called ‘Tranche B’ generators. They must have their permits in place, and start complying with the conditions, by 1 January 2019 or before their contract starts.

The Environment Agency and Natural Resources Wales (NRW) have extended this date. For the latest date you must get your permit, see:

Here are the requirements to meet Tranche A status and qualify for transitional arrangements.

Qualifying for Tranche A – less than 1MWth

A generator with a rated thermal input of less than 1MWth is classed as Tranche A if it meets any of these conditions:

  • its under a capacity agreement from the 2014, 2015 or 2016 capacity auctions (regardless of when the generator came into operation)
  • its under an agreement to provide a balancing service entered into before 31 October 2017
  • an application for a FIT preliminary accreditation was received by the Gas and Electricity Markets Authority before 1 December 2017

Where an aggregator is involved, the date of the capacity agreement is the date of the contract between the aggregator and the National Transmission System Operator.

Qualifying for Tranche A – between 1MWth and under 50MWth

A generator with a rated thermal input of between 1MWth and under 50MWth is classed as Tranche A if it meets any of these conditions:

  • it came into operation before 1 December 2016 or it’s under a capacity market agreement or a balancing service contract from the 2014, 2015 or 2016 capacity auctions (regardless of when the generator came into operation)

  • an application for a FIT preliminary accreditation was received by the Gas and Electricity Markets Authority before 1 December 2016

Where an aggregator is involved, the date of the capacity agreement is the date of the contract between the aggregator and the National Transmission System Operator.

A contract is the binding agreement between the National Transmission System Operator and the supplier – this is a legal contract. For a balancing service, a Short Term Operating Reserve (STOR) contract is made when National Grid issue a STOR Tender Acceptance. That creates the STOR contract for the provision of the service.

Deadlines you must meet

The permitting date is the date by which you must have a permit in place.

If you have aggregated your generators into a specified generator, the term ‘relevant date’ is also used. This is the earliest date by which you must have your permit in place. You work out your relevant date by taking all generators on your site and assessing which has the earliest permitting date.

The compliance date is the date by which a specified generator needs to comply with the permit conditions. Read the guidance Specified generator: comply with permit conditions.

Use this information to work out the:

  • permitting and compliance date for an individual specified generator
  • relevant date and compliance date for an aggregated specified generator

Deadlines for individual specified generators

To work out your permitting date and compliance date for an individual specified generator, you must work out the following:

  • whether your generator is Tranche A or Tranche B
  • its rated thermal input
  • its emissions
  • the number of hours it operates for each year

‘Operating hours’ is the number of hours the combustion plant is operating and discharging emissions to air. Do not include start up (SU) and shut down (SD) periods. You must minimise SU and SD times.

See how to work out the deadline for a specified generator site.

Deadlines for Tranche B specified generators

All Tranche B generators must meet these deadlines. The:

  • permitting date (or relevant date) is 1 January 2019 or the date the new generator was commissioned
  • compliance date is 1 January 2019

If operations started after 1 January 2019, your permitting date and compliance date are the same – the date you commissioned the specified generator.

These dates also apply to Tranche A operators who become Tranche B operators because they signed up to a new capacity market, balancing service or FIT contract after 31 October 2017 and it remained in place after 31 December 2018.

If the new contract date is after 1 January 2019, your permitting date and compliance date are the same as the new contract date.

Deadlines for Tranche A specified generators 5MWth to 50MWth

For Tranche A generators between more than 5MWth and less than 50MWth, the deadline depends on the level of emissions and operating hours.

For generators with emissions above 500mg/Nm3 (STP, 15% O2) and more than 50 operating hours a year (aggregated hours) the:

  • permitting date (or relevant date) is 1 October 2019
  • compliance date is 1 January 2025

For generators with emissions below 500mg/Nm3 (STP, 15% O2) or 50 operating hours or less a year (aggregate hours) the:

  • permitting date (or relevant date) is 1 January 2025
  • compliance date is 1 January 2025

If a Tranche A generator more than 5MWth to 50MWth, entered into a capacity market, balancing service or FIT contract before 1 December 2016 and it ends after 1 January 2025, this end date becomes the compliance date. It must not participate in any other contracts for this to apply.

Deadlines for Tranche A specified generators 1MWth to 5MWth

For Tranche A generators 1MWth to more than or equal to 5MWth the:

  • permitting date (or relevant date) is 1 January 2030
  • compliance date is 1 January 2030

If a Tranche A generator 1MWth to 5MWth entered into a capacity market, balancing service or FIT contract before 1 December 2016 and it ends after 1 January 2030, this end date becomes the compliance date. It must not participate in any other contracts for this to apply.

Deadlines for Tranche A specified generators less than 1MWth

For Tranche A generators less than 1MWth the:

  • relevant date is 1 January 2030
  • compliance date is 1 January 2030

If a Tranche A generator less than 1MWth entered into a capacity market, balancing service or FIT contract before 31 October 2017, and it ends after 1 January 2030, this date will become their compliance date. It must not participate in any other contracts for this to apply.

Aggregating generators and deadlines for a specified generator site

Follow these steps to work out the relevant date (earliest permitting date) and compliance date for aggregated generators that are a specified generator site.

Step 1

Identify Tranche A and Tranche B status for each generator on the site.

Step 2

Calculate the total rated thermal input of the specified generators on the site. Add together the rated thermal input of all the generators (both Tranche A and B but not any excluded generators).

Different deadlines apply if the total rated capacity is between 1MWth and 5MWth or more than 5MWth. If it exceeds 50MWth you’ll need an IED installations permit.

Step 3

Calculate the total number of operating hours a year of your specified generator site. Include Tranche As and Bs, but not excluded generators. Identify if the aggregated hours are less than or more than 50 hours per year.

Do not add the operating hours of each generator together. Each site hour can include one or more generators. For example, you have 3 generators running for exactly the same 400 hour time period – the total operating hours is 400 hours. Or you operate half of your generators for 12 hours and half for 24 hours – the total is 24 hours because the generators are running for different time periods.

Step 4

Assess if any Tranche A generator’s NOx emissions will be less than or more than 500 mg/Nm3 per year (STP, 15% O2).

Deadlines if you have any Tranche B generators on your site

If you have any Tranche B generators on your specified generator site, your relevant date (earliest permitting date) and compliance date is 1 January 2019 or the date it’s commissioned.

Deadlines if you only have Tranche A generators on your site

If you only have Tranche A generators on your specified generator site, work out your relevant date (earliest permitting date) and compliance date as follows.

The total capacity of all the Tranche A generators is more than 5MWth

If at least one of your Tranche A generators is emitting more than 500mg/Nm3 (STP, 15% O2) and operating for more than 50 hours a year, your:

  • permitting date (relevant date) is 1 October 2019
  • compliance date is 1 January 2025

Your permitting date (relevant date) and compliance date is 1 January 2025 if all of your Tranche A generators meet one of these conditions:

  • emitting less than 500mg/Nm3 (STP, 15% O2)
  • operating for less than 50 hours a year

If a Tranche A generator more than 5MWth to 50MWth entered into a capacity market, balancing service or FIT contract before 1 December 2016 and it ends after 1 January 2025, this end date becomes the compliance date.

It must not participate in any other contracts for this to apply.

Total capacity of all the Tranche A generators is less than 5MWth

Your permitting date (relevant date) and compliance date is 1 January 2030.

Types of permit

There are 3 types of specified generator environmental permit:

  • standard rules permit (low risk)
  • simple bespoke permit (low risk)
  • complex bespoke permit

Before you apply for the environmental permit you must be able to demonstrate you can comply with specified generator environmental permit conditions.

Check what to do if you have an existing:

Contact your regulator

England

Contact the Environment Agency

General enquiries

National Customer Contact Centre
PO Box 544
Rotherham
S60 1BY

Monday to Friday, 8am to 6pm

Wales

Contact NRW.

Published 15 July 2019
Last updated 5 September 2019 + show all updates
  1. Corrected the criteria for qualifying for Tranche A status 5 to 50MWth generators.
  2. The Natural Resources Wales Regulatory Decision has been extended to 31 October 2019.
  3. Changed the 'and' to 'or' in the first bullet under the heading 'Qualifying for Tranche A – between 1MWth and under 50MWth'.
  4. First published.