The comparison has to include everything that ownership carries: calibration, spares, storage, insurance and the cost of capital committed.

The project-peak problem

Commissioning demand is concentrated at the end of a construction programme. For a period of weeks or months, several circuits, bays or units need testing at once, and the equipment that covers the normal workload is not enough.

The peak then ends. The equipment that was bought for it becomes spare capacity that still requires calibration, storage and insurance, and whose value depreciates whether or not it is used.

The alternative is to hire the additional capability for the duration of the peak and release it afterwards. The cost is higher per unit of time, and it ends when the peak does.

Cost comparison: rent versus buy for a short programme

The crossover point is usually longer than a single project. A peak that recurs across several projects justifies ownership because the equipment is used between the peaks; a peak that occurs once rarely does.

Availability and lead time of rental units

Specialist high-voltage test equipment is not available from every hire company, and the units that are available may be committed to other projects at the moment the peak arrives. The lead time for a rental unit has to be established against the programme.

Where the equipment is scarce, the availability risk is real: a peak that coincides with other operators’ peaks may find nothing available, and the consequence is a delay to the commissioning programme.

The practical response is to reserve the equipment in advance against the programme dates and to have a contingency for the case where it is not delivered. A reservation with a defined release clause costs less than the delay it prevents.

Calibration and condition of rented equipment

A hired instrument without a current certificate is unusable for any test that has to be reported. The certificate should be supplied with the equipment and checked on arrival, including its scope against the ranges that will be used.

The condition on arrival should be recorded, with photographs where the equipment is expensive or where the hire terms are strict. That record is the reference for the condition on return and it prevents a dispute about damage that was pre-existing.

The certificate chain behind the calibration supplied with a hire unit has to be checkable, with the traceability requirements described in the NIST handbooks and the accreditation framework described by bodies such as ILAC. Where the equipment is used on acceptance testing, the record content that a reviewer expects is set out in the independent acceptance practice published by NETA.

The accessory list should also be checked. A set that arrives without the leads or the coupling it needs may be technically available and practically unusable, and the missing item is discovered on site rather than at the depot.

Operator competence with unfamiliar sets

A team works fastest with the equipment it knows. An unfamiliar set takes longer to set up, its configuration is more likely to be mistaken, and its results are read against a less familiar interface.

Those costs are real and they do not appear in the rental comparison. Where the hire introduces an unfamiliar instrument, the arrangement should include a briefing or support from the supplier, and the programme should allow for the additional setup time on the first few jobs.

Where the same equipment is likely to be hired repeatedly, the argument for buying strengthens: the familiarity becomes an asset that is retained rather than paid for again at each peak.

Insurance, transport and damage liability

The hirer is normally responsible for the equipment from delivery to collection. That includes transport damage, loss and damage caused during use, and the terms should be established before the equipment arrives.

The definition of fair wear matters as much as the value insured. Consumable items, worn leads and cosmetic damage are treated differently by different hire terms, and the difference determines who pays at the end of the hire.

The transport arrangement should also be settled, including who loads and unloads and what equipment is needed at each end. A set that requires lifting equipment at both ends is a mobilisation that has to be planned rather than assumed.

Hybrid models that work well

The most common hybrid is to own the equipment used continuously and hire the capability needed only at peaks. That keeps the familiar equipment in the team’s hands and covers the peak without committing capital to capacity that will be idle.

A second hybrid is to own the instrument and hire the accessories specific to one project. A set with the right range and an accessory that is only needed for one circuit type is a set where the accessory can be hired rather than purchased.

A third is a shared arrangement between operators or between divisions, where equipment is transferred to whichever programme needs it. That requires an arrangement for calibration, condition and responsibility that is worth establishing in writing before the transfer rather than during it.

A decision rule by peak duration

A practical rule has three parts. For a peak shorter than a defined duration, and for equipment that will not be used between peaks, hire. For equipment used continuously, buy. For a recurring peak, compare the total cost of ownership over the period the peaks cover against the cost of hiring for the same period, including the calibration and training that ownership carries.

The rule should state what the comparison includes: purchase, calibration over the period, spares, storage, insurance, training and the residual value. Leaving any of those out biases the comparison towards buying.

The rule should also state the availability assumption. If the decision to hire depends on the equipment being available when needed, that assumption should be stated and tested, because it is the assumption that carries the programme risk. Support and hire arrangements for equipment are described under testing services and OEM/ODM solutions; the equipment range is listed under all electrical testing equipment; distribution arrangements for operators who supply through a channel are described under become a partner; the measurement system requirements that rental equipment has to satisfy are set out in IEC 60060-2; and utility procurement practice for test equipment fleets is coordinated through CIGRE study committees and published by EPRI.