Headroom instrument
Three questions. Your capacity, in your own numbers.
Say what you run, how much of it, and the power you hold. The dashboard reads from your first answer and narrows with each one. Then read the capacity released and the data centre capex it avoids.
Quick start
Each quick start answers all three questions. Change any answer and the dashboard follows.
Question 1
What do you run?
Pick from 96 systems in the hardware register. Where the vendor publishes a draw it fills in; where it does not, type what yours pulls.
NVIDIA HGX H100 8-GPU baseboard
node, 8 accelerators each, 5.6 kW, vendor figure
96 of 96 match, first 6 shown.
Question 2
How much of it?
Racks, accelerators or megawatts: whichever you know. The fleet sizes itself in whole units.
1,785 nodes, 14,280 accelerators, 10 MW of draw. Your own figures.
Question 3
What power do you hold?
Site IT power at the rack input, and the PUE of the hall. The PUE sets the cooling line.
Your dashboard
Fit, capacity, revenue, energy.
Measured: up to 21% less GPU die power on NVIDIA H100 NVL, over 48 hours, with paired arms under an equal power cap. Every figure below is modelled from it and your answers.
- Fleet today
- 10 MW
- Managed, stated to conservative
- 8 MW
- Power you hold
- 10 MW
Fit
Does the fleet fit the power you hold, and by how much.
- Spare today, unmanaged
4 kW
your own figureYour power less your fleet's draw. Managed, 2 MW is left: see Capacity.
- Reduction we model
15% to 21%
modelledBALANCED, from the conservative reading to the stated one.
- Margin against what you need
+15 to +21 points
modelledThe reduction we model, less the reduction you need.
Your fleet fits the power you hold today. Managed, the same envelope carries the extra capacity below, with no new connection and no build.
Capacity
What now fits inside the same power.
- Power this frees
2 MW
modelled10 MW of draw x 15% to 21%.
- Nodes that now fit beyond your fleet
318 to 475 nodes
modelledThe power left once managed, in whole nodes of 5.6 kW.
- Accelerators that now fit beyond your fleet
2,544 to 3,800 accelerators
modelledThose nodes x 8 accelerators each.
- Power left once managed
2 MW
modelledThe power you hold less what the managed fleet draws.
Revenue
What released capacity earns where you sell it, and the build you do not fund.
- Revenue from released capacity
£2m to £3m
modelledeach yearAccelerators that now fit, at £1,600,000 per MW year and 70% utilisation.
- Capital avoided
£14m to £20m
modelledone-offPower this frees x £9,500,000 per MW to build.
Selling released capacity and not funding the next build are two readings of the same megawatt: count one, not both.
Renting capacity rather than holding the power? The saving lands as less power drawn by the accelerators you run, inside the capacity you already contract.
Energy
Energy you no longer buy, and heat the hall no longer has to reject.
Energy waits for how your fleet runs across a day, asked below.
- Step 1
Run it here
Your inputs and one measured coefficient, in your browser.
- Step 2
Send yourself the working
Ask below, then download the document built from your figures.
- Step 3
A three week baseline on your fleet
Your own measurements replace the modelled figures.
- Step 4
A call
On what the baseline found, with the people who decide.
Assumptions
The figures the dashboard runs on.
Each one shows its default and where it came from. Type your own and the dashboard follows.
- Default£ per MW
Default £9,500,000 per MW. Ofgem, data centre connection reforms consultation, 29 July 2026: average capital cost per megawatt, a stated assumption rather than a market price.
- Default£ per MWh
Default £110 per MWh. A working figure for a large industrial connection. Your contract price is the one that counts.
- Quick start£ per MW year
Set by the quick start at £1,600,000 per MW year; default £1,200,000 per MW year. A working figure at full utilisation. Counted only where you sell capacity, at your own rate.
- Defaultratio
Default 1.25. A working figure for a modern hall. It sets the cooling line and nothing else.
- Default%
Default 70%. A working figure for a sold fleet. It scales revenue and accelerator hours.
- Where these go
Every value here travels with your link and your request. The ones you change are listed beside their defaults.
Operating mode
Choose the mode. Balanced, the production default and the mode the measured run used, holds throughput.
Balanced shows the measured figure: up to 21% less GPU die power on NVIDIA H100 NVL over 48 hours, with managed and baseline arms under an equal cap. Performance and Green show the bands from the presets the runtime reads at boot, and the arithmetic uses the middle of each.
Against every other route
The same capacity, priced in time and capital.
| Route to more compute | Time | Capital | What you get |
|---|---|---|---|
| A new grid connection | 5 to 7 years | Grid and civil works | More megawatts, eventually |
| New switchgear and distribution | 30 to 54 weeks | Capital project | More megawatts, eventually |
| More accelerators | Lead time plus install | Hardware capital | No help. The envelope is the limit |
| ADAPT, one software install | Hours | None | Capacity released from hardware already racked |
The assessment
What the assessment adds.
The dashboard reads your fleet against the power you hold. This reads how your day runs and what runs on it. Two attributions sit at equal weight, each with its basis.
How your fleet runs most of the day
Work arriving and finishing, power moving as it does: the pattern the measured run was taken on, and the hours this arithmetic counts. Idle hours are left out, so the figure errs low.
Nothing is assumed. The engine asks for the day shape instead of reading one in.
What runs on it
In your words. The split by class is optional: it describes the estate and reads each class against the mode, it does not enter the arithmetic.
Split the day by class, per cent (optional)
Two readings
Two attributions of the same coefficient, at equal weight.
One answer below completes the reading. Every field changes the result on screen.
- Tell us how your day splits across the three bands. All three are needed.
What would unlock a reading
Across a normal day, how does your fleet split between busy and changing, idle, and pinned at its limit?
This sets how much of the measured saving your day carries. It moves the answer more than anything else here.
Choose the shape of your day above.
What does one of your racks actually pull, measured, rather than its rated draw?
Your measured draw turns the saving into an electricity line, in megawatt hours a year and what they cost.
How many months until new power would actually energise for you?
On most estates in a connection queue this turns out to be the largest single line on the page, and it is entirely your own figure.
What does one accelerator produce, in whatever unit you think in?
States the extra capacity as output rather than as hardware.
Who is reading
Optional, and none of it changes a number. It travels with your request, so the reply starts from your situation rather than from a form.
Your name and email go in the request below. Everything set here goes with them.
The request
Ask for the assessment of this reading.
Your answers, the dashboard, the assumptions you set and everything below the questions go with it.
An engineer reads the figures and writes back with the working and what a baseline on your fleet would involve.