A temporary power budget has seven lines, and most overruns come from three of them. The seven are supply acquisition, distribution hardware, installation and maintenance labour, fuel, energy, metering and recharge, and demobilisation. The three that go wrong are the ones treated as fixed when they are variable: fuel since the 2022 red diesel change, labour on a site that keeps reconfiguring, and the energy nobody can allocate because it was never metered at the boundary. Build the budget from a distribution design, not from a schedule of rates.
STAT
Since 1 April 2022 the construction sector has had no entitlement to rebated red diesel. Entitlement was restricted to qualifying purposes such as agriculture, horticulture, forestry, fish farming, rail and non-commercial heating, which means construction plant and site generators now run on full-duty fuel. Any generator hours estimate carried over from a pre-2022 benchmark understates the fuel line. Source: HM Government, Reform of red diesel and other rebated fuels entitlement
Key takeaways
| Topic | In brief |
|---|---|
| Supply acquisition | Grid connection is a quoted charge with a lead time. Generator is immediate with a fuel tail. |
| Hardware | Buy or hire follows programme length, not unit price. |
| Labour | The line most often estimated once and consumed continuously. |
| Fuel | Full-duty diesel since April 2022. Old benchmarks are wrong. |
| Recharge | Needs a MID-approved instrument at the boundary, decided before energisation. |
Line one: acquiring the supply
The first fork is a DNO connection, generators, or both, and it is a cashflow decision as much as an engineering one.
A distribution network operator connection is a quoted charge. Ofgem approves the methodologies DNOs use to calculate those charges rather than approving the charges themselves, and each DNO is required to review its Connection Charging Statement at least once a year. This means there is no national number to budget against. You get a quote for your site, from your DNO, and the only way to hold the date is to request it early.
One detail worth capturing at budget stage: where a temporary connection is later disconnected, the charging methodology allows a credit for the net value of the equipment recovered. That is a small credit against a large cost, but it is a credit, and it is routinely forgotten at final account.
Generators invert the profile. There is no connection lead time and no civils, so the capital exposure is small and immediate. The cost lives in fuel and servicing, which is a running cost through the whole programme, and it is sensitive to how well the machine is sized. A generator running far below its rating burns fuel per kWh at a poor rate, which is a design failure that only ever shows up in the fuel budget.
On longer projects the practical answer is often both, grid as the primary supply with generators for isolated areas or standby. That is a legitimate configuration and it needs care with earthing and transfer arrangements. The sizing method behind either choice is covered in more detail in specifying temporary power distribution for a UK site.
Line two: distribution hardware, and whether to buy or hire
The hardware line covers the incomer, the main board, sub-boards, cabling, transformers and the tool-supply transformers that step down to 110V centre-tapped-to-earth.
The buy-or-hire question is usually decided on unit price and should be decided on programme length and redeployment. A board that will sit on one site for four years and then move to the next one is a different purchase from a board needed for eight weeks. Robustness matters here for a budget reason rather than a quality reason: a board that survives being lifted, moved and re-sited repeatedly stays out of the replacement line.
Two specification details belong in the budget rather than in a later variation. First, current transformers, which on TSR-Elsite temporary power supply cabinets are included in the delivery as standard. Second, space reserved for kWh meters, which costs nothing to specify at order and is disruptive to retrofit.
| Line | Driver | Common error |
|---|---|---|
| Supply acquisition | DNO quote or generator capital | Assuming a national rate exists |
| Hardware | Programme length, redeployment | Choosing on unit price alone |
| Labour | Site reconfiguration rate | Estimated once, consumed continuously |
| Fuel | Generator hours at full duty | Using a pre-2022 benchmark |
| Energy | Actual kWh drawn | No allocation because no metering |
| Metering | Recharge boundaries | Decided after energisation |
| Demobilisation | Strip-out, make good, recovery credit | Omitted entirely |
Line three: installation and maintenance labour
This is the line most often estimated as a one-off installation and then consumed as a continuous service.
A construction site does not hold still. Boards move as the structure rises, feeds get extended, lighting follows the work face, and every one of those movements is labour. On long projects the realistic model is a permanent or near-permanent presence rather than a mobilisation followed by call-outs.
There is also a statutory inspection and test regime sitting on top of it. HSG141, HSE’s guidance on electrical safety on construction sites, is now in its second edition dated April 2023 and supports duties under CDM 2015, the Electricity at Work Regulations 1989 and PUWER 1998. It is guidance rather than law, and the duty it supports is not optional. Budget the competent person’s time, not just the installer’s.
Line four: fuel, and why old benchmarks are now wrong
Any fuel figure carried across from a project that started before April 2022 is understated, because the entitlement to use rebated red diesel was removed from the construction sector on 1 April 2022. HMRC’s Excise Notice 75 sets out the current rules on using rebated fuels in vehicles and machines.
The practical consequence for a budget is twofold. Generator hours became a materially more expensive unit, which raises the value of right-sizing and of load management. And the business case for hybrid or battery configurations changed at the same moment, because the thing they displace got more expensive.
If the estimate for this line came from a benchmark rather than from a load profile, it is worth rebuilding from the load profile.
Line five: energy, and the allocation problem
Energy consumed is separate from fuel burned, and on a grid-supplied site it is usually the larger of the two.
The problem is rarely the total. It is the allocation. A principal contractor recharging energy to subcontractors, or reporting energy per package, needs the measurement to exist at the point where the commercial boundary sits, and that decision has to be made before energisation. Unmetered periods cannot be reconstructed afterwards. There is no retrospective fix, only an argument.
This is where operational monitoring and commercial metering get conflated, and conflating them inflates cost. Monitoring is continuous and operational: is this board near capacity, are the phases balanced, is voltage drifting. Its accuracy requirement is sufficient to act on. What board-level monitoring gives the budget is per-board consumption and usage against available capacity, retained for the site history, which is enough to settle most internal allocation arguments and to size the next project honestly.
Metering is commercial and periodic. Where a kilowatt hour will be invoiced to another party, the instrument falls under Directive 2014/32/EU on measuring instruments. On Spine, MID-approved energy metering is an optional accessory fitted where a billing boundary exists; the standard Spine consumption measurement is explicitly not a MID-approved meter. Fitting approved instruments everywhere is waste. Fitting none of them where money changes hands is a dispute.
Draw the billing boundaries on the distribution schematic before energisation. Afterwards, all you have is an argument and no data.TSR-Elsite
Line six and seven: contingency and demobilisation
Two items complete the budget and both are commonly missing.
Contingency against reconfiguration. Programmes change, phases overlap, and the winter load arrives whether or not the site was sized for it. A project energised in summer on summer demand meets a different reality when heating and drying load lands in late autumn. That is a capacity question with a cost attached.
Demobilisation. Strip-out, making good, recovery of hired equipment and, where a temporary DNO connection is disconnected, the equipment recovery credit noted above. It is a small line in a large budget and it is almost always the one that was never entered.
Summary
Budget temporary power from a distribution design rather than a schedule of rates, and price seven lines: supply acquisition, hardware, labour, fuel, energy, metering and demobilisation. Get the DNO quote early because there is no national rate. Rebuild the fuel line from a load profile rather than a pre-2022 benchmark, because construction lost red diesel entitlement on 1 April 2022. Decide the recharge boundaries before energisation, because unmetered periods cannot be reconstructed. To work through a temporary power budget for a UK site, see worksite power supply or get in touch: sales@tsr-elsite.fi or +358 9 4555 588.
Frequently asked questions (FAQ)
Is there a standard cost per kVA for temporary power on a UK site?
No. Distribution network operators calculate connection charges using methodologies approved by Ofgem rather than a national tariff, and each DNO reviews its Connection Charging Statement at least once a year. The only reliable figure is a quote for your site from your DNO, which is why requesting it early matters.
How did the red diesel change affect construction power budgets?
The construction sector lost its entitlement to rebated red diesel on 1 April 2022, with entitlement restricted to qualifying purposes such as agriculture, forestry, rail and non-commercial heating. Site generators now run on full-duty fuel, so any generator hours estimate benchmarked from an earlier project understates the fuel line.
Should we buy or hire distribution boards?
It follows programme length and redeployment rather than unit price. A board serving a multi-year project and then moving to the next one is a different decision from one needed for a few weeks. Durability belongs in the budget conversation because replacement is a real line.
When do we need MID-approved metering rather than monitoring?
When a kilowatt hour will be invoiced to another party. That instrument falls under Directive 2014/32/EU. Operational monitoring, which answers whether a board is near capacity or whether phases are balanced, has a different accuracy requirement and does not need approval. On Spine, MID-approved metering is an optional accessory rather than a platform-level certification.
What gets missed most often in a temporary power budget?
Three things: continuous labour rather than one-off installation, the recharge metering decision, and demobilisation. The metering one is the least recoverable, because unmetered periods cannot be reconstructed after the fact.
Does HSG141 add cost to the budget?
It adds the competent person’s time to the labour line rather than a separate cost. HSG141 is HSE guidance, second edition April 2023, supporting duties under CDM 2015, the Electricity at Work Regulations 1989 and PUWER 1998. The guidance is not law, but the duties it supports are statutory.
Sources
- HM Government, Reform of red diesel and other rebated fuels entitlement
- HMRC, Using rebated fuels in vehicles and machines (Excise Notice 75)
- Ofgem, A guide to electricity distribution connections policy
- HSE, HSG141 Electrical safety on construction sites (second edition, 2023)
- Directive 2014/32/EU on measuring instruments (EUR-Lex)
- Spine real-time remote monitoring system (product page)
- TSR-Elsite, Temporary power supply cabinets with meter