Cloud storage draws power all day, every day. The six FlashArray storage systems that BlackBox Hosting runs across two UK data centres use about 4.95 kW between them, or an estimated 43 MWh of electricity a year. On the UK grid that comes to about 5.7 tonnes of carbon dioxide equivalent (CO2e) a year, before cooling.
Storage is one part of our data centre energy consumption. Servers and cooling sit on top of it, so this page also explains how a whole site adds up and how to turn kWh into carbon. The figures come from a self-service sustainability report we generated in Pure1 on 30 September 2026. Pure1 is the monitoring service from Pure Storage (now Everpure), which makes the arrays. We publish them because any carbon neutral hosting claim should rest on numbers you can check.
Quick facts
- What it covers: six FlashArray storage systems across two UK data centres, taking up 18 rack units.
- Power: about 4.95 kW in use, against a combined peak of 6.3 kW.
- Electricity: an estimated 43 MWh a year, or about 7,200 kWh for each array.
- Carbon: about 5.7 tonnes CO2e a year on the UK government’s 2026 factor, or 16.3 tonnes on the report’s US basis.
- Lifetime: 251 tonnes CO2e over 10 years in the report’s model, 90.6% of it from electricity in use, cooling included.
What does our storage energy report measure?
The report covers our six FlashArray storage systems and nothing else. Pure1 estimates each array’s power draw from the data the array sends back, then projects a year of electricity and carbon from that draw. Our servers and network equipment are outside it, as are the cooling and power systems of both data centres. All six arrays sent enough data for the annual summary.
The arrays are Pure Storage FlashArray systems. The product line kept its name when Pure Storage announced its new name, Everpure, on 23 February 2026, and so did Pure1. We generated the report ourselves from the Reporting area of Pure1, so it rests on Pure’s own estimates. It is not an independent audit or verification.
| Measure | Figure in the report |
|---|---|
| Storage systems | Six FlashArray systems, three in each of two UK data centres |
| Space | 18 rack units (nine in each data centre) |
| Power in use | 4.95 kW (2.42 kW and 2.53 kW in the two data centres) |
| Peak power | 6.3 kW (3.08 kW and 3.22 kW) |
| Heat output in use | 16,901 BTU an hour (8,262 and 8,639) |
| Electricity a year | About 43 MWh (21 MWh and 22 MWh) |
| Carbon a year, report’s US basis | 16,272 kg CO2e |
| Carbon a year, UK 2026 factor | About 5,700 kg CO2e (our calculation) |
| Effective capacity | 644 T in use of 1,741 T usable (T is the report’s capacity unit) |
| Pure1 insights raised | None |
Pure1 can raise four kinds of insight, which are its efficiency recommendations. They cover an older model due an upgrade, older flash modules due an upgrade, a seven-day average power draw close to peak, and too little work for an array to run efficiently. None was raised on our arrays. Read that as nothing flagged rather than a clean bill of health. The same report shows zero appliances installed in its genealogy section, for six arrays that are plainly running, so a zero does not always carry meaning.
What do the figures mean in plain terms?
Each array draws a little over 0.8 kW on average and uses about 7,200 kWh of electricity a year. Pure1 projects that draw across all 8,760 hours of a year, which is how 4.95 kW becomes about 43,400 kWh. The arrays ran at about 79% of the peak power in the report, and each of the 18 rack units they fill drew about 275 watts.
| Unit | Power in use | Electricity a year | Carbon a year, UK 2026 factor |
|---|---|---|---|
| All six arrays | 4.95 kW | 43,388 kWh | 5,682 kg CO2e |
| Each data centre (three arrays) | 2.42 kW and 2.53 kW | 21,208 kWh and 22,180 kWh | 2,777 kg and 2,905 kg CO2e |
| Each array, on average | 0.83 kW | 7,231 kWh | 947 kg CO2e |
| Each rack unit, on average | 275 W | 2,410 kWh | 316 kg CO2e |
| Any 1 kW, run for a year | 1 kW | 8,760 kWh | 1,147 kg CO2e |
These are our calculations from the report’s power figures. A rack unit is one standard slot of height in an equipment rack. None of the rows includes cooling.
Key takeaway: anything that draws 1 kW without a break uses 8,760 kWh a year, whether it powers storage, a server or a network switch. On UK grid electricity in 2026, that is a little over one tonne of CO2e before cooling.
How much energy does a data centre use?
There is no single figure. A data centre’s energy use is the power its IT equipment draws, plus the overhead of keeping that equipment cool and powered. Our storage arrays are one slice of the IT load in two data centres. Power usage effectiveness (PUE) measures the overhead, which applies on top of every kWh the IT equipment uses.
The Scottish Government’s annex on power usage effectiveness splits a data centre’s load in two. IT load covers servers, storage and network equipment. Facility load covers cooling, heating, ventilation, battery backup and power distribution. To estimate a whole site, add up the IT load over a year and multiply it by the site’s PUE for the same year.
We have not published a PUE for our data centres, so this page gives no whole-site figure. Storage is the part we can show from the equipment’s own reporting.
What is power usage effectiveness (PUE)?
Power usage effectiveness (PUE) is the total energy a data centre uses divided by the energy its IT equipment uses. A PUE of 1.0 is the best possible score, because it would mean every kWh reaches the IT equipment. A PUE of 1.4 means the site uses 1.4 kWh in total for each 1 kWh its servers, storage and network kit use. Lower is better.
An international standard sets out data centre PUE as a key performance indicator: ISO/IEC 30134-2:2016, listed by BSI with a publication date of 19 April 2016. A PUE means little without the period it covers, because cooling needs change through the year. Ask for an annual figure and its dates.
Pure’s lifetime model for our arrays assumes cooling adds 40% to the energy the arrays use. The report labels this a PUE of 0.4, but a PUE cannot be lower than 1. Read as an overhead, it matches a PUE of about 1.4 if cooling were the only overhead. It is Pure’s assumption, not a measurement of our data centres. On that assumption, cooling would add about 17 MWh a year to the arrays’ 43 MWh.
Key takeaway: PUE multiplies every kWh of IT load. A provider’s PUE is only useful with the dates it covers and a note of how it was measured.
Why does the carbon figure depend on the grid?
Because the same kWh produces different emissions on different grids. The report converts electricity to carbon with US Energy Information Administration statistics, which work out at about 0.375 kg per kWh. The UK government’s 2026 factor for UK grid electricity is 0.13096 kg CO2e per kWh. So the same 43 MWh is 16.3 tonnes on the US basis and about 5.7 tonnes on the UK one.
The UK factor comes from the UK government’s greenhouse gas conversion factors for 2026, published on 11 June 2026 and checked on 19 October 2026. It is a location-based figure: the average for the grid where the electricity is used. According to the factors’ own guidance, the government’s Environmental Reporting Guidelines require the location-based figure for Scope 2 electricity. A market-based figure, which reflects contracts such as certificate-backed renewable tariffs, may be reported only in addition to it.
The 2026 UK factor is also much lower than the 2025 one. Part of the reason is a change of method. The government now uses more recent data on the generation mix, which cuts the lag between the data and the reporting year from two years to one. Check which year’s factor any comparison uses, and do not set a 2026 figure against one worked out with an older factor.
One more detail matters less than it looks. The US statistics count carbon dioxide only, while the UK factor is CO2e and adds small amounts of methane and nitrous oxide. The carbon dioxide part of the UK factor is 0.12943, so the difference in gases explains very little of the gap between the two bases.
Key takeaway: always ask which electricity factor sits behind a carbon figure. The same 43 MWh can be 16 tonnes or under six, depending on the grid assumed.
How do you turn kWh into a carbon figure?
Multiply the electricity in kWh by a conversion factor for the right country and year. For UK electricity in 2026, the government factor is 0.13096 kg CO2e per kWh. The government also advises counting losses in transmission and distribution, at 0.01299 kg per kWh, and treats those as Scope 3. Our worked example below uses the arrays’ own figures.
- Start with the power draw in kW. Our arrays draw 4.953 kW in total.
- Multiply by the hours. A full year is 8,760 hours, so 4.953 kW becomes about 43,388 kWh.
- Add the site overhead if you know the PUE, by multiplying the kWh by it. We leave this step out, because we have not published a PUE.
- Multiply by the generation factor for the reporting year. 43,388 kWh multiplied by 0.13096 gives 5,682 kg CO2e.
- Add transmission and distribution losses if you report them. 43,388 kWh multiplied by 0.01299 gives 564 kg, for about 6,246 kg in all.
- If your electricity comes through a certificate-backed renewable tariff, you may add a market-based figure, alongside the location-based one.
| GOV.UK 2026 factor (checked 19 October 2026) | kg CO2e per kWh | Reported as | Applied to our 43,388 kWh |
|---|---|---|---|
| UK electricity generated | 0.13096 | Scope 2 at sites you control; Scope 3 for managed assets | 5,682 kg |
| Transmission and distribution losses | 0.01299 | Scope 3, voluntary but best practice | 564 kg |
| Well-to-tank, generation | 0.03682 | Scope 3, voluntary | 1,598 kg |
| Well-to-tank, transmission and distribution | 0.00359 | Scope 3, voluntary | 156 kg |
| The report’s US basis, for comparison | About 0.375 | Not a UK reporting factor | 16,272 kg |
Well-to-tank factors cover extracting, refining and transporting the fuels burned to make electricity. Reporting them is voluntary. If you include them, the government’s guidance says to apply them consistently across every fuel and activity in your report, not to electricity alone.
Where does storage’s footprint come from?
The carbon footprint of data storage comes mostly from the electricity it uses. The report’s lifetime model puts our six arrays at 251 tonnes CO2e over 10 years, on the same US grid basis. Electricity in use, with the assumed cooling, makes up 90.6% of that. Making the arrays accounts for 9.8%, and reuse at end of life gives a small credit.
| Stage, over 10 years | kg CO2e | Share of total |
|---|---|---|
| Materials | 21,692 | 8.6% |
| Transport during manufacturing | 2,013 | 0.8% |
| Assembly and testing | 450 | 0.2% |
| Packaging | 403 | 0.2% |
| Electricity in use | 162,718 | 64.7% |
| Cooling (Pure’s assumption of 40%) | 65,087 | 25.9% |
| End-of-life treatment | -876 | -0.3% |
| Total | 251,486 | 100% |
Transport in this model covers only transport during manufacturing. The report leaves out delivery to us. The end-of-life credit is for parts of products that Pure reuses after customers return them.
On UK electricity the share from use would be smaller. Our rough calculation puts it at about 77%, holding the 2026 UK factor flat for 10 years and keeping Pure’s 40% cooling assumption. Electricity would still be the largest part by far.
The report’s ESG page sets out Pure Storage sustainability goals that point the same way. Pure says use of its sold products made up 70% of its total emissions in its 2022 financial year. Its 2030 target is to cut those emissions per effective petabyte by 66% against its 2020 financial year. It says it has cut them by 25% since setting that goal.
Key takeaway: for storage, the power a system draws over its life matters far more than how it was made. Efficiency in use is where most of the carbon sits.
What drives data storage energy consumption?
Data storage energy consumption depends mostly on how much hardware is switched on, because powered-on equipment draws electricity whether or not anyone reads the data. After that come how fully the hardware is used, how much data reduction fits onto each drive, and the age of the equipment. Our arrays drew about 4.95 kW while using about 37% of their usable effective capacity.
| Driver | What it means | What our report shows |
|---|---|---|
| Hardware switched on | Each powered array draws electricity around the clock | Six arrays in 18 rack units, drawing 4.95 kW |
| How fully it is used | Pure1 suggests adding workloads to an under-used array to improve its energy efficiency | About 37% of usable effective capacity in use; no “not enough workloads” insight raised |
| Data reduction | Effective capacity counts data after reduction, so more data fits on each drive | Capacity reported in effective terms: 644 T used of 1,741 T usable |
| Model and module age | Pure1 flags older models and older flash modules for upgrade | No upgrade insight raised |
| Power near peak | A seven-day average near peak is a prompt to check the environment | Not raised; average draw about 79% of peak |
Effective capacity is the amount of data an array can hold once data reduction, such as deduplication and compression, has done its work. The report states capacity in these effective terms, not as raw drive space.
All-flash storage keeps data on solid-state flash rather than spinning hard disks, so it has no motors or platters to power. As a general principle that helps with power and rack space, but the size of any gain depends on the systems compared. Our report measures no disk system, so we give no comparison figure here.
How do you report cloud hosting in your emissions?
Usually as Scope 3. The UK government’s conversion factors say electricity used at a site or in an asset you do not own or operate, with space in a data centre as the example, is reported as Scope 3. They also say this reporting is voluntary. Electricity at sites you own or control is Scope 2. Either way, IT sustainability reporting for hosting needs kWh figures from your provider.
The government’s guidance describes the three scopes like this. Scope 1 is direct emissions from activities you own or control. Purchased electricity, heat, steam and cooling fall in Scope 2. Scope 3 is other indirect emissions from sources you do not own or control, such as materials you buy or business travel.
Colocation needs a closer look. If you lease rack space and run your own equipment, the guidance says organisations using the financial control or equity share boundary should report an operating lease as Scope 3, and other leases as Scope 2. Whoever prepares your emissions report should confirm which applies to you.
Some organisations must report. Under the Streamlined Energy and Carbon Reporting (SECR) rules, UK quoted companies, large unquoted companies and large limited liability partnerships report their energy use and greenhouse gas emissions. GOV.UK encourages other companies to report on the same basis, voluntarily.
The method for purchased electricity is also under review. The GHG Protocol’s Scope 2 Guidance standardises how companies measure emissions from purchased electricity, and the GHG Protocol held a public consultation on it from 20 October 2025 to 31 January 2026. Check which version your reporting framework follows.
What should you ask a hosting provider about energy and carbon?
Ask for numbers you can check. Start with the electricity used by the equipment behind your services and the factor used to turn it into carbon. Then ask for the site’s PUE with its dates, and what has been independently verified. The Competition and Markets Authority’s Green Claims Code, published on 20 September 2021, expects up-to-date, credible evidence behind a green claim.
| Question to ask | Why it matters | What a useful answer includes |
|---|---|---|
| How many kWh does the equipment behind our services use? | Energy is the base of every carbon figure | The kWh, the period and whether it is metered or estimated |
| Which emission factor do you use, for which country and year? | The grid assumed can change the result almost threefold | A location-based factor for the reporting year, with any market-based figure alongside |
| What is the site’s PUE, and over what period? | PUE scales every kWh of IT load | A measured annual figure with its dates |
| Do the figures include cooling and transmission losses? | Leaving them out makes the total smaller | A plain list of what is in and what is out |
| What is independently verified, and by whom? | A self-service estimate is not a verification | The standard, the verifier and the period covered |
| Is the claim carbon neutral or net zero? | The two allow different use of offsets | The standard behind the claim and the offsets used |
Data centre sustainability claims are only as good as the numbers behind them. Ask these questions of any provider that talks about sustainable data centres, including us. We set out more warning signs in our article on how to spot greenwashing in green hosting. Sustainable IT starts with figures you can check.
What green IT steps can you take with your own data?
Green IT starts with keeping less. Every copy you store sits on hardware that draws power around the clock, so the biggest step for your digital carbon footprint is deciding what you no longer need. Retention periods, deletion on schedule and a sensible number of backup copies all reduce the capacity you pay to keep switched on.
- List your main data stores, what each one holds and who owns it.
- Set retention periods. For personal data, the Information Commission (formerly the ICO) says in its guidance on the storage limitation principle that you must not keep it for longer than you need it. It also says to review what you hold and to erase or anonymise data you no longer need. The regulator notes that this guidance is under review after the Data (Use and Access) Act 2025.
- Delete on schedule, including old test, staging and migration copies.
- Move rarely used data to an archive tier where your provider offers one, and check how quickly you can get it back.
- Keep the backup copies your recovery plan needs and no more. Our guide to the 3-2-1 backup rule explains the usual minimum: three copies, on two types of storage, with one offsite.
- Ask your provider for capacity reports, and compare what you pay for with what you use.
Key takeaway: the greenest copy of your data is the one you no longer need to keep. A retention policy cuts risk and storage at the same time.
Is a carbon neutral data centre the same as a net zero data centre?
No. ISO 14068, the international standard on carbon neutrality, treats it as quantifying a footprint, reducing it and offsetting what remains, with reductions taking priority over offsets. For an organisation, net zero usually means something stricter: emissions cut until only residual emissions remain, with offsetting limited to removal credits. The standard says it does not set requirements for net zero.
Those definitions come from the introduction to BS ISO 14068:2026, which BSI published on 30 September 2026. It replaced the 2023 edition, BS ISO 14068-1:2023, which BSI lists as withdrawn on 16 September 2026. A green data centre claim usually rests on one of these two terms, so check which one is meant and which standard sits behind it.
BlackBox Hosting holds an ISO 14068-1:2023 carbon neutrality verification issued by BSI. We explain what that standard requires in our guide to what ISO 14068 carbon neutrality means. Pure’s own goal, as the report states it, is net zero by 2040 for its Scope 1 and market-based Scope 2 emissions. The same page says that in its 2023 financial year Pure committed to setting science-based targets for Scopes 1, 2 and 3.
How BlackBox Hosting can help
BlackBox Hosting runs managed private and sovereign cloud from UK data centres. We are ISO 14001 certified, and our carbon neutrality verification under ISO 14068-1:2023 was issued by BSI. This report shows the storage side of our energy use from the equipment’s own data. If you are working out the footprint of your hosting, or comparing providers on the questions above, talk to an expert.
Frequently asked questions
It depends on how much hardware is switched on. BlackBox Hosting’s six FlashArray storage systems use an estimated 43 MWh of electricity a year, drawing about 4.95 kW in total, according to the Pure1 report we generated on 30 September 2026. That is about 7,200 kWh a year for each array, before cooling.
Storage uses electricity all day, every day. In the report’s lifetime model for our arrays, that electricity is most of the footprint. How much harm it does depends on how efficient the hardware is, how fully it is used and how clean the grid behind it is.
For our six arrays, about 5.7 tonnes CO2e a year using the UK government’s 2026 factor for UK electricity, or 16.3 tonnes on the US grid basis in the report. Neither figure includes cooling. Over 10 years, the report’s model puts the total at 251 tonnes on the US basis, including manufacture.
The report uses US grid statistics, which work out at about 0.375 kg per kWh. The UK government’s 2026 factor for UK electricity is 0.13096 kg CO2e per kWh, so the same 43 MWh comes to about 5.7 tonnes rather than 16.3.
Power usage effectiveness (PUE) divides a data centre’s total energy use by the energy its IT equipment uses. A PUE of 1.0 would mean no overhead at all. The figure is only meaningful with the period it covers and a note of how it was measured.
Usually Scope 3. The UK government’s conversion factors treat electricity used in an asset you do not own or operate, such as space in a data centre, as Scope 3 and voluntary. If you lease rack space for your own equipment, the lease type and your reporting boundary decide which scope applies.
It can, when deleting data means less storage hardware has to be bought or kept switched on. Powered-on storage draws electricity whether or not anyone reads the data. A retention policy, applied on a schedule, is the way to make deletion add up.