Estimating electrical load is one of the most consequential technical judgements an occupier team makes during site selection, yet it is also one of the most frequently deferred until the lease is already in heads of terms. Getting the number right early — before a shortlist is fixed — prevents the kind of discovery that collapses transactions: a building whose transformer capacity cannot support a data-dense occupier, or a floor plate whose riser configuration was designed for a previous generation of office density. This guide walks through the method step by step, from first-principles demand analysis through to the power statement that belongs in every occupier requirements brief.
Why Electrical Load Belongs in the Brief, Not the Diligence
Most occupier requirements briefs open with headcount, square footage, lease term and budget. Electrical load rarely appears until a building surveyor or M&E consultant is engaged — which typically happens after the shortlist is already set. By that point, the team has invested adviser hours, management time and often an exclusivity period in a building that may be fundamentally unsuitable.
The cost of late discovery is not just the aborted transaction. It is the compression of the shortlist that follows, the re-engagement of landlords who have already moved on, and the reputational cost of a prolonged process. Treating electrical load as a brief requirement rather than a diligence surprise changes the economics of the entire search.
Landlords and their agents know what their buildings can deliver. Agents conducting the search know which assets to exclude. The result is a shorter cycle from brief to shortlist, and a shortlist that survives technical scrutiny.
There is also a regulatory dimension. Many jurisdictions now require occupiers and landlords to report energy consumption data, and some are moving toward mandatory disclosure of electrical infrastructure capacity as part of the letting process. Anchoring the brief to a real load estimate positions the occupier correctly for those obligations before they become enforceable requirements.
Step One — Define the Use Profile Before Touching a Calculator
Electrical load estimation starts with use, not with formulas. The first task is to build a use profile: a plain-language description of every activity that will consume power in the occupied space, organized by category. Office workstations are one category. Server rooms or IT closets are another. AV and conferencing infrastructure, print rooms, catering and kitchen equipment, specialty manufacturing or lab equipment, and EV charging all belong in separate rows of the same analysis.
The use profile is not a floor plan and it is not a headcount table, though it draws on both. It is a functional description of the tenant's operation, organized around power-consuming activities rather than around space types. A media production company and a professional services firm may have identical headcounts and identical floor areas, but their use profiles — and therefore their load estimates — will be radically different.
Gathering the use profile requires direct conversation with the occupier's facilities and technology leads. Those conversations often surface requirements that were invisible in the original brief: a trading floor that needs redundant feeds, a research function that runs computing clusters overnight, or a food service component that requires a commercial kitchen hook-up. Each of those requirements carries a load implication that must be reflected in the brief.
One practical method is to walk through an existing occupied space with the facilities manager and document every piece of equipment that is plugged in or hard-wired, organized by zone. This is not always possible — early-stage relocations often involve occupiers who do not yet know exactly how they will configure the new space — but even a partial inventory produces a more defensible estimate than a rule-of-thumb figure applied to gross floor area.
Step Two — Apply Connected Load and Demand Factor Principles
Once the use profile is assembled, the next step is to convert equipment lists into electrical load figures using connected load and demand factor analysis. Connected load is the sum of the nameplate ratings of every piece of equipment that could draw power simultaneously. Demand load is the fraction of connected load that is realistically expected to operate at the same time, during peak conditions.
For a standard office environment, the connected load will almost always exceed the practical demand load by a significant margin. Not every workstation monitor is at maximum brightness simultaneously. Not every task light is on. The demand factor — which expresses the ratio of expected simultaneous demand to total connected load — is the mechanism that converts a theoretical maximum into a realistic planning figure. Demand factors vary by use type and should be verified with a qualified M&E consultant for each specific occupier.
The calculation is straightforward in principle. For each equipment category in the use profile, multiply the unit load (in watts) by the quantity, then multiply by the demand factor for that category. Sum the results across all categories to reach a peak demand estimate for the occupied space. Add a design margin — typically expressed as a percentage of the calculated peak — to account for future growth and equipment upgrades that the occupier cannot yet anticipate.
That design margin is not arbitrary. For an occupier planning a five-to-ten-year term, the margin needs to reflect realistic business growth assumptions, technology trends that increase per-device consumption, and the possibility that the space will be reconfigured during the term. A margin that is too thin will force a costly infrastructure upgrade mid-lease. A margin that is too generous will translate into a brief that disqualifies buildings unnecessarily.
Step Three — Separate Base Building Supply from Tenant Supply
A load estimate that does not distinguish between base building electrical supply and tenant supply is not a useful planning document. These are two different systems, and confusing them is one of the most common errors in early-stage occupier briefing.
Base building supply refers to the electrical capacity that the landlord provides as part of the shell and core: main switchgear, transformers, rising main capacity, and the connection to the grid via the utility service. Tenant supply refers to the dedicated capacity allocated to the tenant's demised space: the sub-metered allocation, tenant distribution boards, and the capacity available for fit-out works.
The key planning question is whether the building's allocated tenant supply — expressed in amperes per floor or kilowatts per square meter — meets the occupier's estimated demand load plus design margin. If it does not, the occupier faces one of three outcomes: negotiate with the landlord for an upgraded allocation, accept a constrained supply and manage operations accordingly, or remove the building from the shortlist.
Understanding this distinction early changes how conversations with landlords are framed. Rather than asking a vague question about power availability, the occupier's team can present a specific requirement and ask the landlord to confirm whether the base building can support it. That is a question that landlords and their technical advisers can answer definitively, which moves the site selection process forward efficiently.
Step Four — Account for Critical Infrastructure and Redundancy
General office loads are relatively predictable. Critical infrastructure loads — data rooms, trading floors, research computing, broadcast or streaming operations — require a different analytical approach because they carry both a higher base load and a redundancy requirement that effectively doubles the electrical capacity needed.
Redundancy in electrical supply is typically expressed using the Tier classification framework developed and maintained by the Uptime Institute for data center infrastructure. While that framework was designed for dedicated data centers, its underlying logic applies to any occupier function where unplanned downtime carries a material operational or financial cost. An occupier whose trading operations require continuous uptime will need to understand whether the building can support a redundant feed configuration.
For non-data-center occupiers, the redundancy conversation is usually simpler but still material. Does the building have a standby generator? What is its capacity, and which circuits does it cover? Is UPS protection available at the building level, or must the tenant procure and install their own? Each of these questions has a load implication that must be reflected in the requirements brief if the occupier's operations genuinely depend on continuous power.
The load estimate for critical infrastructure should be calculated independently from the general office load and presented separately in the brief. This allows landlords and their technical teams to assess feasibility at a category level rather than treating the whole figure as a single undifferentiated number. It also makes the negotiation of landlord contributions to infrastructure works more structured and defensible.
Step Five — Convert the Estimate into Brief Language
A load estimate expressed only in kilowatts is not a requirements brief. The brief needs to translate the technical figure into language that a landlord, agent or site selection team can act on without an M&E consultant in the room. That translation involves three elements: a headline requirement, a minimum specification, and a confirmation request.
The headline requirement states the estimated peak demand for the occupied area and notes the design margin that has been applied. The minimum specification states the minimum tenant allocation that the occupier will accept — the floor below which a building cannot qualify for the shortlist regardless of its other attributes. The confirmation request asks the landlord's technical team to provide documented evidence that the base building supply and the proposed tenant allocation can meet the stated minimum specification.
Including a clear minimum specification in the requirements brief gives agents and landlords a filter they can apply immediately, which reduces the volume of unsuitable properties that reach the shortlist stage.
This three-part structure disciplines both sides of the conversation. It prevents landlords from offering vague assurances that a building should be able to accommodate the requirement. It gives the occupier's team a clear pass/fail criterion to apply during initial market engagement. And it creates a paper trail that is useful if a technical issue emerges later in the process.
The brief should also specify the metering arrangement the occupier expects — whether the electrical supply will be sub-metered to the tenant separately, whether smart metering will be required for energy reporting purposes, and whether the landlord or tenant is responsible for the metering infrastructure. These details affect fit-out cost allocations and lease negotiation, and they are far easier to establish at the brief stage than to retrofit into a heads of terms that has already been agreed.
How to Estimate Electrical Load for an Occupier Requirements Brief — Working Through a Hypothetical Scenario
To make the methodology concrete, consider a hypothetical professional services occupier taking approximately twenty thousand square feet across a single floor. The use profile includes approximately two hundred workstations, a server room housing twelve rack units, two large conference rooms with full AV infrastructure, a staff café, and a printing and reprographics area. The occupier also wants provision for up to twenty EV charging points in the car park, which is within the demised area.
Working through connected load by category: standard office workstations and monitors at roughly one hundred and fifty watts each produce a connected load of thirty kilowatts for that category. Server racks at an average of five kilowatts per rack produce sixty kilowatts. AV infrastructure across two conference rooms might total eight kilowatts connected. Catering equipment in the café might total twenty kilowatts. Reprographics, perhaps four kilowatts. EV charging at seven kilowatts per point for twenty points produces a connected load of one hundred and forty kilowatts. The total connected load for this hypothetical example is therefore two hundred and sixty-two kilowatts.
Applying demand factors — these are illustrative figures for the purpose of this example and should always be verified with a qualified M&E consultant — reduces the figure substantially. Office workstations might carry a demand factor of sixty to seventy percent; catering, seventy to eighty percent; EV charging, fifty to sixty percent depending on charging behavior assumptions; server infrastructure, eighty to ninety percent given continuous operation. Applying mid-range demand factors across the categories reduces the hypothetical peak demand to somewhere in the range of one hundred and seventy to one hundred and ninety kilowatts. Adding a twenty percent design margin for a five-year term produces a brief requirement of approximately two hundred to two hundred and thirty kilowatts of tenant allocation.
That figure — expressed as a minimum tenant allocation of two hundred kilowatts — becomes the electrical load requirement in the brief. Every building on the candidate list is then assessed against that number as a hard filter during the site selection process, before any site visits are arranged or any detailed financial modelling is conducted.
Integrating Load Requirements into the Site Selection Scoring Matrix
A load estimate that lives only in the requirements brief does not stay useful for long. To maintain its value through a multi-building shortlist process, the electrical load requirement needs to be integrated into the scoring matrix that the advisory team uses to evaluate and compare candidate properties.
The scoring matrix for a site selection exercise typically spans location criteria, financial criteria, physical criteria and operational criteria. Electrical load belongs in the physical criteria column, and it should carry both a threshold weight — buildings that do not meet the minimum are excluded, regardless of score — and a gradient weight for buildings that exceed the minimum by meaningful margins. A building that can provide substantially more tenant allocation than the stated minimum is more future-proof than one that barely clears the threshold, and that difference should be visible in the score.
When a building is excluded from the shortlist because its electrical allocation falls below the stated minimum, that exclusion should be documented against the criterion that was established before the search began. Recording the reason — rather than simply dropping the building from the list — creates an auditable rationale that is useful if the shortlist is later challenged or if the same property is reconsidered after an infrastructure upgrade.
That structure is exactly what a load-integrated scoring process requires: a place where the technical requirement is anchored to the brief and carried through the evaluation rather than existing in a separate spreadsheet that may or may not be consulted consistently.
Engaging Building Technical Teams — What to Ask and When
The brief is a communication tool, and its effectiveness depends on how it is used in early conversations with landlords and their technical advisers. The sequence matters: the load requirement should be raised at the first substantive conversation about a property, not after a tour has been arranged and commercial terms have begun to be discussed.
The initial question should be framed as a straightforward technical enquiry: can you confirm the available tenant electrical allocation for the floor or floors under consideration, expressed in kilowatts, and confirm whether this can support the stated minimum requirement? A landlord or asset manager who cannot answer that question from existing documentation is a signal that the building's technical data room is not in good order, which is itself a useful piece of information.
If the answer is positive, the follow-up question is about the confirmation mechanism: will the landlord provide a written technical statement, and at what point in the transaction process? For buildings where the landlord is willing to invest in infrastructure upgrades to meet an occupier's requirement, the follow-up question is about the scope, timeline and cost-sharing arrangement for those works. These are lease negotiation questions, but they are much better answered before heads of terms than during the legal drafting phase.
Financial Modelling and Electrical Load — the Connection
Electrical load capacity is not just a technical requirement; it has direct financial implications that belong in the lease economics analysis. Fit-out costs, landlord contribution negotiations, ongoing energy costs and the risk of mid-lease infrastructure upgrades all flow from the load estimate, and all of them affect the occupier's effective occupancy cost.
The total cost of occupying a space is influenced by the level of electrical infrastructure already in place at the building. Where the base building can support the occupier's requirement without additional investment, the tenant avoids capital expenditure on transformer upgrades, additional riser capacity or bespoke sub-metering infrastructure. Where the base building cannot support the requirement, those costs either fall to the tenant directly or become a subject of landlord contribution negotiation. Either way, the financial model for the deal should reflect the gap between what the building provides and what the occupier needs.
Occupier advisory teams that integrate the load estimate into their financial comparison workbooks are able to present a more complete picture of occupancy economics across shortlisted buildings. The comparison goes beyond headline rent and service charge to include infrastructure-related fit-out cost differentials, which can be material for data-intensive occupiers.
Documenting Load Assumptions for the Technical Due Diligence Phase
When an M&E consultant is engaged to review a building in detail, the load estimate from the requirements brief gives them a starting point that reflects the occupier's actual operations rather than a generic office density assumption. The value of that starting point depends on how clearly the assumptions behind the estimate are recorded.
Every input to the connected load calculation — equipment types, quantities, unit loads, demand factors, design margin — should be recorded alongside a note of where the figure came from: measured from the existing space, provided by the IT team, drawn from published equipment specifications, or estimated based on comparable projects. That level of documentation allows the M&E consultant to review each assumption independently, validate those that are well-supported, and challenge those that may need to be revised in light of building-specific conditions.
When the diligence review identifies a discrepancy between what the building can deliver and what the brief required, clear documentation of the original assumptions makes it straightforward to trace where the gap arose. The consultant can work from the recorded inputs to recalculate the estimate under revised conditions and quantify the impact on the occupier's infrastructure requirements. That recalculation may support a lease negotiation, justify an infrastructure contribution request, or inform a decision to reopen the shortlist.
Keeping the Load Estimate Current Through the Transaction
Requirements briefs are living documents. Headcount projections change, technology decisions evolve, and the occupier's operational model may shift between the moment the brief is written and the moment the lease is signed. The load estimate needs to be reviewed and updated whenever a material change occurs in any of the underlying assumptions.
The most common trigger for a mid-process revision is a change in IT strategy. An occupier who decides during the lease negotiation to migrate workloads from on-premises infrastructure to cloud-hosted services will have a substantially lower server room load than the original estimate assumed. Conversely, an occupier who decides to bring workloads back in-house, or who acquires a business unit with significant computing requirements, will need to increase the estimate. Neither of these changes is unusual, and both can materially affect which buildings remain qualified candidates.
The review process should be structured rather than ad hoc. Scheduling a review at the point of shortlist finalisation, another at heads of terms, and a final review before fit-out works are specified will catch most material changes before they create operational or financial problems down the line. Each review should be documented with a date, a summary of what changed, and an updated estimate figure.
Occupier teams that treat the load estimate as a fixed document written once at the start of the process and never revisited are taking on unnecessary risk. The estimate is only as accurate as its inputs, and those inputs change. Building structured review moments into the transaction timeline is not additional overhead; it is the basic discipline that prevents a mid-lease infrastructure problem from being traced back to an assumption that was outdated by the time the lease was signed.
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