Coalburn1 BMU-4
104 MW, about 177 MWh (1.7 hours, measured from its behaviour) in Lothian and Borders. Everything on this page is read from published data for the 364 days to 27 September 2026, or is labelled as an estimate.
What it is
| Registered power | 104 MW balancing mechanism registration |
| Storage duration | 1.7 hours measured from twenty one days of behaviour |
| Charging zone | Lothian and Borders |
| Connection site | Coalburn 400kV |
| Balancing mechanism unit | T_COALB-4 |
Who owns it and who trades it
| Traded by | Alcemi Storage Developments 4confirmed, Elexon's register |
| Owned by | ALCEMI STORAGE DEVELOPMENTS 4 LIMITED |
| Owner established from | connection register applicant |
| Ultimately | Copenhagen Infrastructure Partners (Alcemi develops) confirmed source |
How we know. CIP's commercial operation release for Coalburn 1.
Market registers name the party that sells into the market, which for a battery is usually an optimiser under contract rather than the owner. Elexon's balancing mechanism unit register names the seller here and the name is checked against it on every build. How we tell them apart
What it earned
| Line | 364 days to 27 September 2026 |
|---|---|
| Balancing mechanism | −£459k |
| Response and reserve auctions auction implied | £0 |
| Capacity market | no agreement we can attach |
| Three lines together | not netted |
Balancing is offer revenue and does not net off the cost of the power. The response and reserve figure is the value implied by the published auction results, award quantity times clearing price times the length of the delivery window, and not a settled payment. Capacity market income is the cleared price raised for inflation where the auction set a base period, split by month on EMRS's weights. Method
Outside the balancing mechanism, derived from the meter
Elexon publishes what this unit's meter recorded every half hour. Take away the balancing volumes NESO accepted and what is left is the position the unit ran outside the balancing mechanism: its wholesale trading, its frequency response delivery, and its losses, together. This unit held no frequency response contract in the window, so the whole position is treated as traded. The volumes are measured. The prices are public benchmarks, not this unit's trades. The product is derived, and is shown apart from the three measured lines above. 147 days to 12 September 2026, 33 of them still provisional in Elexon's settlement runs. Method and caveats
| Line | MWh or £ |
|---|---|
| Metered export, what crossed the meter out | 6,296 MWh |
| Metered import, what crossed the meter in | 8,117 MWh |
| Equivalent full cycles, everything sent out over one full charge | 35.5 over 147 days, 88.2 a year at that rate |
| Apparent meter to meter efficiency | 78%, plausible: losses plus a standing load that is material against a modest throughput |
| Balancing offers accepted | 194 MWh |
| Balancing bids accepted | 2,975 MWh |
| Position outside balancing, export | 8,794 MWh |
| Position outside balancing, import | 7,834 MWh |
| Valued at the market index, sold | £1.2m |
| Valued at the market index, bought | £765k |
| Outside balancing, net, at the index | £438k |
| Balancing and outside balancing together | £189k £4.51/kW/yr |
When it moved, against when power was dear
Across every half hour this unit was metered the market index averaged £108.51. What it sent out was worth £136.74 a megawatt hour at that same index, 1.26 times the average. What it took in was worth £97.65, 0.90 times. Selling above one and buying below one is a unit positioned into the dear half hours and out of the cheap ones. It measures the half hours it chose, not the price anyone paid it, which is not published.
What it paid to buy energy back
When NESO accepts a bid, this unit delivers less than it had already sold, or takes more in. It pays for the energy it no longer delivers, and that payment is most of what makes the balancing figure above negative. Whether that is a cost or a margin depends on the price it paid. Across 2,975 MWh of accepted bids it paid an average of £93.91 a megawatt hour. The market index averaged £151.60 across those same half hours, so it bought back at £57.69 a megawatt hour below the going price.
| Price it paid | Volume | Average | Cash |
|---|---|---|---|
| below zero | 207 MWh | −£10.09 | £2k received |
| £0 to £25 | 63 MWh | £20.64 | £1k |
| £25 to £50 | 234 MWh | £42.63 | £10k |
| £50 to £75 | 157 MWh | £70.90 | £11k |
| £75 to £100 | 688 MWh | £83.27 | £57k |
| above £100 | 1,626 MWh | £124.12 | £202k |
On 207 MWh the price was below zero: NESO paid this unit an average of £10.09 a megawatt hour to take energy, £2k in all. That is a constrained network with more generation on it than it can move.
The other direction, offers, is much smaller here: 194 MWh where NESO asked for more, paid at an average of £159.62 against an index of £135.02.
Checks this unit did not pass cleanly. Published anyway, because a flagged figure with its flag is more use than a blank.
- only 147 of 364 days metered
Where it stands
| Balancing incomewhole fleet, £/kW/yr | 22nd percentile98 units | |
| Balancing incomeScotland peer group | 41st percentile28 units | |
| Balancing income1.7 hour duration cohort | 15th percentile60 units | |
| All three measured lineswhole fleet, £/kW/yr | 10th percentile229 units | |
| Energy sent outhours at full power | 2nd percentile96 units | |
| Energy taken inhours at full power | 13th percentile96 units |
Percentiles, so 90 means better than nine in ten of the cohort named beside it, on that measure alone, over the same 364 days. Rates are pounds per kilowatt per year, annualised over the days the unit has been on the system, the same figures the performance league ranks on. A high position in the taken-in table is not a fault: a constraint asset is paid to charge, and charging is its job.
The nearest comparables
The five nearest in size in Scotland, and this battery among them, ranked by what each was paid for every kilowatt it holds over the 364 days to the same date. They run for about the same length of time. Same market, same rules, same weather.
| Battery | MW | Hours | Measured, per kW |
|---|---|---|---|
| Wishaw BESS | 51 | 2h | £44.7/kW/yr |
| Auchteraw | 49 | 2h | £33.3/kW/yr |
| East Ayrshire (KILSB-2) | 52 | 2h | £3.1/kW/yr |
| East Ayrshire (KILSB-1) | 53 | 2.1h | £3.0/kW/yr |
| Shilton Lane BESS | 40 | 2h | £2.2/kW/yr |
| Coalburn1 BMU-4this battery | 104 | 1.7h | not netted |
The three lines are not added together for this site. It paid £585k to charge and the lines we can measure paid it £126k. The energy it bought was sold in the wholesale market and nothing published measures that sale, so subtracting one from the other would show a loss it does not make. Sites in this position are usually constraint assets, paid to absorb wind the network cannot move south.
See it on the map
Every figure on this page traces to a published file. If something here is wrong about your asset, the methods section says how to tell us.