Markets

Energy project modelling in the UK electricity market (GB)

The Great Britain (GB) electricity market covers England, Scotland and Wales, and includes wholesale, balancing, ancillary services and capacity markets, plus green certificate schemes. Gridcog models how batteries, solar, wind, EV charging and flexible loads earn across these markets, half-hour by half-hour, with GB network tariffs, so you can test a project before you invest.

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  • GB’s T-4 and T-1 Capacity Market auctions contracted about 1.8 GW of battery obligations in early 2026, on contracts of up to 15 years.

    Laura Hoffmann-Ostenhof, July 2026

  • Britain’s demand connection queue grew from 41 GW to 125 GW in seven months, with at least 80 GW of the increase from data centres, on a system that peaks at about 45 GW.

    Ofgem, cited by Joshua Elliott, August 2026

  • In Pete Tickler’s model of a Maidstone supermarket, a 500 kWh / 250 kW battery earned £19,885 in 2024 trading three wholesale markets under P415, against £7,152 from bill savings alone.

    Pete Tickler, February 2025

How the market works

How does the UK electricity market work?

The UK has two electricity markets. England, Scotland and Wales share one Great Britain (GB) market with the same rules and incentives, while Northern Ireland is part of the all-island Single Electricity Market with Ireland. The GB market runs at 50 Hz and has a national wholesale price: one power price for the whole country in each settlement period.

Most power in GB is traded well before delivery. Large generators submit their planned dispatch to the system operator as a Physical Notification at least 60 minutes before delivery. The National Energy System Operator (NESO) then balances supply and demand in real time through the Balancing Mechanism, and anyone left with an imbalance is cashed out at the System Price.

Which markets can you trade power in in GB?

Seven, from forward contracts years ahead to the cash-out price after delivery. Most trading is in the day-ahead auctions and the intraday continuous market. An EFA block, used in many GB contracts, is a four-hour block; the power day starts at 23:00 and has six of them.

  1. Years to days before delivery

    Forward and over-the-counter (OTC)

    Bilateral trades, on exchange or through brokers, mainly to hedge

    Granularity: Seasons, quarters, months, weeks, EFA blocks, peak or baseload

  2. 09:20 and 09:50 GMT the day before

    Day Ahead Hourly Auction

    Pay-as-clear auction on EPEX and N2EX; the most liquid market and the usual reference price

    Granularity: 24 hourly contracts

  3. 15:30 GMT the day before

    Day Ahead Half-Hourly Auction

    Pay-as-clear auction on EPEX, run after weather and demand forecasts have updated

    Granularity: 48 half-hourly contracts

  4. 17:00 the day before; 08:00 on the day

    Intraday Auctions 1 and 2

    Pay-as-clear auctions on EPEX, much less liquid

    Granularity: 48 and 30 half-hourly contracts

  5. Up to 15 minutes before delivery

    Intraday Continuous

    24/7 order book on EPEX, most active in the two hours before delivery

    Granularity: Half-hourly (most liquid), hourly and EFA blocks

  6. Real time

    Balancing Mechanism

    NESO accepts bids to turn down and offers to turn up, to keep supply and demand in balance

    Granularity: Any duration, from minutes to hours

  7. Known after each settlement period

    System Price (cash-out)

    Elexon cashes out imbalances at the price set by the marginal Balancing Mechanism action

    Granularity: 48 half-hourly prices

A deeper dive into wholesale energy markets in GB

Why do flexible assets trade between markets?

Because prices change between markets as forecasts change. A battery, EV fleet or gas peaker can re-adjust, or ‘churn’, its traded position through the day. In Genna Boyle’s example, a 1 MW battery that locked in a £60 spread in the Day Ahead Hourly Auction made £115 for the same volume by re-trading in the half-hourly and intraday continuous markets.

How volatile are GB power prices?

Volatile enough to make market access valuable. In 2024 the average daily spread in GB’s Day Ahead Hourly Auction was £54/MWh, with a maximum of £341/MWh, against about 1.5p/kWh in a typical business supply contract. On 8 January 2025, low wind and high demand pushed intraday prices to several times the day-ahead price, with gas plants setting the System Price at around £3,000/MWh. There were 149 hours of negative day-ahead prices in 2025.

  • £54/MWh

    Average daily spread in GB’s Day Ahead Hourly Auction in 2024

  • £341/MWh

    Maximum daily spread in the same auction in 2024

  • Around£3,000/MWh

    System Price set by gas plants on 8 January 2025

  • 149 hours

    Of negative day-ahead prices in 2025

Understanding negative pricing and price volatility

Thinking Energy

GB energy market videos

Short explainers from the Gridcog team on GB markets, rules and how to model them.

 

What is the P510 code modification?

May 2026 · 4:31

 

Modelling the increased TNUoS charges for 2026/27

April 2026 · 4:01

 

Modelling P415 for a GB logistics site and battery

March 2026 · 4:46

 

Understanding Quick Reserve as a developer

August 2025 · 3:34

 

Overcoming grid constraints as a large energy user

June 2025 · 3:55

 

Modelling flexible assets in the GB energy market

May 2025 · 2:53

Generation and demand

What powers the GB electricity market?

A diverse mix that has changed dramatically in the last 20 years. Coal-fired generation was completely phased out in 2024. Gas still supplies a large share of demand, alongside a fast-growing offshore wind fleet in the North Sea, nuclear, biogas, solar PV and imports from neighbouring countries through large interconnectors. GB also has one of the largest fleets of utility-scale batteries in the world.

  • 4.8 GW

    Utility-scale batteries in GB by May 2025, with 6.6 GWh of storage

  • 45 GW

    Peak demand, reached on 11 February 2026

  • 33%

    Forecast rise in electricity use across GB industries by 2040, against 2025 (DESNZ)

  • Up to40 GW

    Utility-scale battery storage by 2050 in NESO’s Holistic Transition scenario

A fast-growing battery fleet

That battery fleet has grown fast. In August 2019, batteries provided 472 MW of the 1 GW of reserve the system operator used to contain a partial blackout, mostly through Firm Frequency Response. By May 2025, GB had over 4.8 GW / 6.6 GWh of utility-scale batteries.

Grid frequency collapse and blackouts in GB, the Iberian Peninsula and Australia explained

How much electricity does GB use, and how is demand changing?

GB’s peak demand is about 45 GW, measured as total demand net of embedded generation; it reached 45 GW on 11 February 2026. Electrification will push consumption up. The Department for Energy Security and Net Zero (DESNZ) forecasts electricity use across industries in Great Britain rising 13% by 2030 compared with 2025, and 33% by 2040, and 80% of new cars sold in 2030 must be zero emission.

Demand from EVs and heat pumps is flexible, so peak demand should rise less than total demand. NESO’s Future Energy Scenarios 2025 put utility-scale battery storage at up to 40 GW by 2050 in its Holistic Transition scenario, with almost 50% of total system flexibility coming from residential and commercial consumers.

Why smart flexibility is critical to a net zero grid

Revenue streams

How do batteries and flexible assets earn money in GB?

By trading across a deep revenue stack. Over the last decade GB has added a wide range of ancillary services which, with a Capacity Market and liquid wholesale trading, give batteries many markets to trade across. Behind-the-meter assets can also earn by cutting network charges and, through P415, by trading wholesale markets.

  • Wholesale
  • Balancing and frequency
  • Capacity and contracts
  • Behind the meter

Wholesale

Wholesale trading

Buy and sell across the day-ahead and intraday markets, churning positions as prices move

Who it suits

Front-of-meter; behind-the-meter through a supplier or P415

Read more

Balancing and frequency

Balancing Mechanism

NESO accepts bids to turn down and offers to turn up, paid at the bid or offer price

Who it suits

Registered Balancing Mechanism units, including aggregated assets

Balancing and frequency

Dynamic frequency response

Dynamic Containment, Moderation and Regulation (the Dx suite) hold capacity to respond to frequency within a second, contracted in EFA blocks

Who it suits

Mainly front-of-meter batteries; metering is stricter than for Static Firm Frequency Response

Read more

Balancing and frequency

Quick Reserve

Reserve dispatched by NESO’s control room, bought a day ahead for each half-hour, with availability payments and pay-as-bid energy payments

Who it suits

Batteries and other fast-responding assets

Read more

Capacity and contracts

Capacity Market

T-4 and T-1 auctions pay the clearing price on de-rated capacity: about 42% for a four-hour asset and 84% for an eight-hour one

Who it suits

Batteries, generators and demand response, on contracts of up to 15 years

Read more

Behind the meter

DNO flexibility services

Distribution network operators (DNOs) pay sites to cut demand where the network is constrained, roughly 3p to 25p per kWh delivered

Who it suits

Behind-the-meter batteries and flexible loads in the right part of the network

Read more

Behind the meter

Network charge savings

Move import away from peak Distribution Use of System (DUoS) and Transmission Network Use of System (TNUoS) charges

Who it suits

Behind-the-meter and co-located sites

Read more

Why ancillary prices fall

GB’s ancillary markets are shallow, so prices fall as batteries connect. When the Dx services launched, NESO’s demand outstripped battery capacity and revenues ran very high for 12 to 18 months. Positive and Negative Quick Reserve cleared at averages of £5 and £4.30/MW/h in July 2025, down from £10 and £7 in February. Model these services with realistic offers-accepted and utilisation rates, and allow for saturation over time.

  • £10 → £5

    Positive Quick Reserve average, £/MW/h, February to July 2025

  • £7 → £4.30

    Negative Quick Reserve average, £/MW/h, February to July 2025

Battery energy storage system (BESS) modelling

Capacity and contracts

Renewable support

Contracts for Difference (CfDs), Renewables Obligation Certificates (ROCs), feed-in tariffs (FiTs) and Renewable Energy Guarantees of Origin (REGOs)

Who it suits

Solar, wind and co-located projects

Read more

01 / 08

P415 and P510

How can behind-the-meter assets trade GB wholesale markets?

Through P415. Since 7 November 2024, this Balancing and Settlement Code modification has let owners of behind-the-meter batteries, EV chargers, generators and heat pumps appoint an independent aggregator, acting as a Virtual Trading Party (VTP), to trade their flexibility in wholesale markets. The site keeps its existing supply contract.

Revenue depends on the deviation volume: the difference between the site’s actual demand and its baseline, multiplied by the wholesale price. GB uses Elexon’s BL01 baseline by default. It suits solar-heavy sites poorly, because the baseline moves with day-to-day solar output, and it needs five eligible days without flexing in any 60-day window, so a site that flexes too often can lose its baseline.

Understanding P415: what it is, who it’s for and how to participateP415: what is the baselining methodology?

What is P415 worth to a business?

Pete TicklerChief Product Officer and Co-Founder

Pete Tickler modelled a 500 kWh / 250 kW battery at a supermarket in Maidstone on 2024 prices, without solar. The site’s energy bill was £85,715 a year before the battery. Each step of market access added value, and full P415 trading across three wholesale markets almost tripled the value of bill savings alone.

Value the battery generated in 2024

  1. 01

    £7,152

    Retail time-of-use supply contract (bill savings only)

  2. 02

    £14,615

    Day-ahead wholesale supply, plus Capacity Market and DNO flexibility

  3. 03

    £16,639

    P415, Day Ahead Hourly only, plus Capacity Market and DNO flexibility

  4. 04

    £19,885

    P415, three wholesale markets, plus Capacity Market and DNO flexibility

The economics of behind-the-meter battery storage, part 2: earning value in energy markets

What changes under P510?

Dan LehmannSenior Energy Analyst

Load-shifting revenue would fall, but reflect real market value. P510 is a proposed modification that would replace P415’s mutualised compensation pot with a bilateral arrangement between supplier and VTP, settling both upward and downward deviations. In Dan Lehmann’s model of a 1 MW / 2-hour battery at a North Wales industrial site, March 2026 revenue fell from about £92k per MW a year under P415 to about £22k under P510.

Payments from the P415 mutualisation pot reached almost £5.5 million in January 2026.

About£92k

Per MW a year under P415

About£22k

Per MW a year under P510

Understanding P510: what it is, how it differs from P415, and what it means for asset owners

Grid connections

How long does a grid connection take in GB, and what’s changing?

Often years. NESO reported a GB connection queue of 750 GW in December 2024, against about 75 GW connected. Connections reform replaces ‘first come, first served’ with ‘first ready and needed, first connected’: only projects with a Gate 2 offer get a confirmed connection date, judged on readiness and fit with the government’s Clean Power 2030 Action Plan.

Ofgem has set deadlines of 31 October 2026 for Gate 2 Phase 1 offers and 31 January 2027 for Phase 2 (decision of 2 October 2026). For smaller projects, Ofgem raised the Transmission Impact Assessment threshold for distribution-connected generation in England and Wales from 1 MW to 5 MW of export capacity in May 2025, removing a step that had delayed some behind-the-meter projects by up to 10 years.

GB grid connection reform and the 5 MW Transmission Impact Assessment threshold

  1. 750 GWGB connection queue reported by NESO, against about 75 GW connected

  2. 1 MW → 5 MWTransmission Impact Assessment threshold for distribution-connected generation in England and Wales

  3. Ofgem decisionRevised timetable for Gate 2 offers

  4. Gate 2 Phase 1Deadline for Phase 1 offers

  5. Gate 2 Phase 2Deadline for Phase 2 offers

What flexible connection options are there in GB?

Four main arrangements, plus bringing your own generation. They trade a firm guarantee of capacity for an earlier, cheaper connection, and differ mainly in how much notice the site gets before its limit drops.

ArrangementHow it worksNotice before a reductionCap on curtailment and compensation
01Timed (scheduled)
The agreement sets the hours, days or seasons when the site must stay below an agreed level; National Grid Electricity Distribution offers a versionKnown in advancen/a
02Flexible now, firm later
The site connects early under restrictions, then converts to firm once reinforcement is complete; Ofgem is developing a staged version for GBKnown in advancen/a
03Active network management (ANM)
An automated system reduces the site’s import whenever the local network nears its limit; the newest connections are curtailed firstLittleAnnual cap on curtailment hours since a 2023 rule change, with compensation beyond it
04Technical Limits
An accelerated non-firm connection where the constraint sits on the transmission networkLittleNo cap and no compensation
05Bring your own generation
On-site storage or generation covers the load whenever grid supply is reducedn/aUsed alongside one of the arrangements above

Modelling curtailment in Gridcog

In Gridcog, a Site Import Schedule applies timed or phased limits, and interval data can represent real-time curtailment. You can then autosize a battery, or a co-located battery and solar, to cover the gap.

Flexible grid connections for data centres: GB and IrelandData centre power modelling

Why co-locate assets behind a GB grid connection?

To use more of a scarce connection. A standalone solar or wind asset uses its grid connection only 10% to 25% of the time, and solar’s load factor in GB is about 11% to 12%. Adding a battery behind the same connection makes better use of it, protects against falling capture prices and earns from GB’s full revenue stack.

  • 10% to 25%

    Of the time a standalone solar or wind asset uses its grid connection

  • 11% to 12%

    Solar’s load factor in GB

Co-located battery storageSolar PV simulationWind farm modelling

How Gridcog models GB

How does Gridcog model the GB electricity market?

With GB’s own markets, tariffs and rules, interval by interval. GB wholesale prices in the Gridcog Library update daily via API, and you can upload your own forward curves. Gridcog co-optimises dispatch across every market a project can access, so the revenue stack reflects the trade-offs between them.

Day Ahead Hourly (N2EX and EPEX), Day Ahead Half-Hourly (EPEX) and Intraday Continuous (EPEX) prices. Set the order markets trade in, the price difference needed before an asset churns, and how often a trader picks the best market.

Bid and offer curves with default accepted percentages from benchmarking by Gridcog’s data and modelling team, or your own curves and acceptance rates.

Dynamic Containment, Dynamic Moderation and Dynamic Regulation (high and low), Static Firm Frequency Response and Quick Reserve, with offers accepted, energy utilisation, bid rounding and trading block durations.

T-1 and T-4 auction results, with asset-level de-rating factors by duration.

DUoS tariffs for every GB distribution network operator (SSEN, SP Energy Networks, Electricity North West, National Grid Electricity Distribution, UK Power Networks and Northern Powergrid), final TNUoS tariffs for 2026/27 with NESO’s five-year forecast, and non-commodity costs such as BSUoS, the Renewables Obligation, CfD levies and the Climate Change Levy.

Model P415 trading through a VTP, test P510 with inter-asset flows priced separately, and apply ANM, timed or phased limits with a Site Import Schedule.

Model CfDs, power purchase agreements (PPAs), tolls, floors and swaps, add each stakeholder, and compare cashflows, internal rate of return (IRR) and net present value (NPV). Download the Investment Case Report for investment committees and lenders.

Modelled in Gridcog

How much does a day-ahead swap steady a GB battery’s revenue?

Considerably. Gridcog Senior Energy Analyst Catalina Villaro modelled a 100 MW, four-hour GB battery trading wholesale and balancing markets, with a financial day-ahead swap on its exports at a fixed £100/MWh. Over the first quarter of 2027, the swap narrowed the battery’s monthly revenue from £13,100–£22,500 per MW to £14,551–£17,304 per MW.

Catalina VillaroSenior Energy Analyst

Monthly revenue per MW, first quarter of 2027

£13,100–£22,500

Without the swap

£14,551–£17,304

With the day-ahead swap at £100/MWh

Swap settlement

  1. January 2027

    £134.1/MWh

    Battery’s captured day-ahead price

    Asset owner paid £414k

  2. February 2027

    About£87.6/MWh

    Battery’s captured day-ahead price

    Asset owner received £132k

  3. March 2027

    £140.3/MWh

    Battery’s captured day-ahead price

    Asset owner paid £505k

What the swap covers

Every exported MWh nets exactly £100 on the day-ahead leg. Charging costs and Balancing Mechanism revenue stay merchant, so the swap steadies revenue without fixing it.

Battery storage offtake agreements: swaps, floors and bankability explained

Sizing a battery or testing its revenue stack in GB?

Model your project in Gridcog

Customers

Which UK teams use Gridcog?

Behind-the-meter developers, battery specialists and advisers to property and public sector estates use Gridcog to model projects in GB. Four have published how.

All case studies

Sustain Commercial Solar

£27m

Behind-the-meter solar and storage, UK

Has modelled about 400 MWh of BESS across 50 sites in Gridcog, uses it for over 80% of client proposals, and estimates about £27m of investment secured over 12 months.

‘We’ve had Gridcog for a year now, and it’s more than paid for itself.’
Nick Elbourne, COO

  • Carb0n

    Real estate energy, UK

    Modelled 3.5 MW of solar car ports with a 4 MWh battery for a landlord, with central energy control across tenants.

    ‘Gridcog gave us the confidence to approach clients with concrete, data-driven solutions.’
    Peter Massie, Head of UK
    Carb0n: read the case study

  • Connected Energy

    Second-life EV battery storage, UK

    Uses Gridcog to find the optimal power and duration for each site, towards a target of 300+ MWh of BESS across the UK, France and Germany by 2028.

    ‘Gridcog has been the only tool we’ve found that lets us analyse revenue potential in such granular detail.’
    Robert Moore, Chief Business Development Officer
    Connected Energy: read the case study

  • Net Zero Advisory

    Public sector decarbonisation, UK

    Models solar, batteries and smart microgrids for public sector estates.

    ‘Gridcog takes something that’s so complex, making it plug-and-play, and gives you the output you need.’
    Chris Scott, Founder
    Net Zero Advisory: read the case study

Experts

Who are Gridcog’s GB market experts?

Gridcog’s London team works with customers across GB and Europe, and writes most of the analysis this page draws on.

  • Genna Boyle

    CCO and Head of EMEA

    Began her career in energy trading at Contact Energy in New Zealand, then helped set up the trading team at Limejump and went on to lead its commercial team.

  • Dan Lehmann

    Senior Energy Analyst, London

    Helps clients model energy markets in the UK and Europe. Before Gridcog, he led the development of smart charging products for fleets at EO Charging.

  • Ashok Willis

    Senior Energy Analyst

    Author of Gridcog’s P415 baselining guide and its analysis of UK grid capacity for large energy users.

  • Joshua Elliott

    Energy Analyst

    Author of Gridcog’s guide to flexible grid connections for data centres in GB and Ireland.

  • Pio Pius

    Business Development Manager, London

    Focused on GB, Ireland and the Nordics.

  • Lizzi Gold

    Business Development Manager, London

    Builds Gridcog’s customer base with utility-scale developers, IPPs and utilities. Before Gridcog, she spent five years at RheEnergise, a long duration energy storage start-up.

Who models GB projects in Gridcog?

Developers and IPPs, investors and funds, energy majors, large energy users and data centres, consultants and e-mobility teams.

Modelling software for renewable developers and IPPsInvestment modelling for funds and investorsEnergy modelling for energy majorsSolar, battery and EV modelling for large energy usersData centre power modellingEnergy modelling software for consultantsFleet electrification and EV charging modelling

Frequently asked questions

No. The GB market covers England, Scotland and Wales. Northern Ireland is part of the all-island Single Electricity Market (SEM) with Ireland, which has its own wholesale, capacity and system services arrangements. So the UK has two electricity markets, each with different rules, prices and network tariffs. See Ireland’s Single Electricity Market (SEM).

Several bodies share the job. The National Energy System Operator (NESO) balances the system in real time, manages grid connections and runs the ancillary services and Capacity Market auctions. Ofgem regulates the market and the network companies. Elexon administers the Balancing and Settlement Code and settles imbalances. Transmission owners and 14 regional distribution networks run the wires, and DESNZ sets energy policy.

No. GB has a single national wholesale price. In its Review of Electricity Market Arrangements (REMA) update of 10 July 2025, the government rejected zonal pricing and kept one national market. It committed instead to a Strategic Spatial Energy Plan and a review of TNUoS charges to send locational signals. Other proposals in that update included shorter settlement periods and a lower Balancing Mechanism entry threshold.

It pays batteries for being available when the system is under stress. They bid into T-4 auctions, four years ahead of delivery, and T-1 auctions, one year ahead, and earn the clearing price on their de-rated capacity: about 42% for a four-hour battery and 84% for an eight-hour one. In early 2026 the two auctions contracted about 1.8 GW of battery obligations.

Yes, through Ofgem’s cap and floor scheme, which runs for up to 25 years. A project earning below the floor gets a guaranteed minimum income, and one earning above the cap returns money to consumers. Projects must deliver at least eight hours of continuous output at full power. In a minded-to decision on 26 June 2026, Ofgem selected 16 projects totalling about 7.6 GW in the first window. See long duration energy storage (LDES).

P415, live since 7 November 2024, lets an independent Virtual Trading Party trade a site’s flexibility in wholesale markets, with suppliers compensated from a shared mutualisation pot. P510 is a proposed change that would replace the pot with bilateral compensation between supplier and VTP, so upward and downward deviations are both settled. Dan Lehmann’s modelling suggests load-shifting revenue would fall, but reflect real market value.

Yes. The Gridcog Library holds DUoS tariffs for every GB distribution network, final TNUoS tariffs for 2026/27 with NESO’s five-year forecast, and non-commodity costs such as BSUoS, the Renewables Obligation and CfD levies. Batteries and flexible loads optimise against these charges and market prices together, so network savings and market revenue come from the same model.

We benchmark it every year. Gridcog compares its modelled revenue for a front-of-meter GB battery with public industry data, and publishes the parameter settings that came out of the exercise, such as 85% round trip efficiency and 90% of capacity registered for ancillary services. GB wholesale prices in the Gridcog Library update daily via API. Compare your project with our benchmark projects.

Request a live demo

Model your GB project in Gridcog

Request a demo and we’ll show you how Gridcog models your project against GB’s markets, network tariffs and connection rules.

The team behind Gridcog

Fabian Le Gay Brereton, Chief Executive Officer and Co-Founder of Gridcog

Fabian Le Gay Brereton

Chief Executive Officer & Co-Founder

Previously co-founded Greensense, acquired by ERM Power (now Shell Energy).

Pete Tickler, Chief Product Officer and Co-Founder of Gridcog

Pete Tickler

Chief Product Officer & Co-Founder

Co-founded Greensense and led digital innovation at ERM Power (now Shell Energy).

Genna Boyle, Chief Commercial Officer and Head of EMEA at Gridcog

Genna Boyle

Chief Commercial Officer & Head of EMEA

More than 10 years in energy strategy, trading and renewables, with senior roles at Battery Optimiser and Limejump.

Which other markets does Gridcog model?

Gridcog supports 40+ markets, including Australia’s National Electricity Market (NEM) and Wholesale Electricity Market (WEM), New Zealand and, in Europe, Ireland, Germany, Spain, Poland, Italy, Portugal, the Netherlands, Belgium and France.

All markets

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