Estimating Market Rent Across a Portfolio

A single tenancy can be assessed by hand. A portfolio of hundreds cannot — at least not with the same rigour per unit, and certainly not on an ongoing basis. Yet this is precisely where the rent optimisation lies: in the units that have drifted below the market over time because no one has had occasion to look. A re-letting from 2019 that was never normalised against the current level. A commercial tenant whose contract has never been adjusted, because the case seemed too small to take up.

Market rent at portfolio level is therefore about two things at once: estimating the rent consistently across many assets, and using that estimate to find the units that can carry an uplift. The first requires a method that can scale without falling apart. The second requires the estimate to be reliable enough to act on. This article walks through how to do both.

Why the single-tenancy method does not scale

For one tenancy the approach is well known: place it in the right regulatory track, find comparable lettings, normalise for condition and contract terms, and document the level. That is the exercise we have covered for both residential and commercial in the article on how market rent is set and substantiated.

The problem is not the method — it is volume and consistency. When the same exercise has to be repeated across a portfolio, three weaknesses emerge:

• The levels drift apart. Two colleagues assessing two similar properties rarely land on the same basis. The difference is invisible until two tenancies in the same building show markedly different rent per m² with no explanation.
• The documentation becomes uneven. Some assessments have a full set of comparables, others have a figure and a gut feeling. It is the uneven documentation that makes a single rejection dangerous — it can set a precedent for the rest of the portfolio.
• It never gets updated. A manual assessment is a snapshot. The market moves, but the old estimates stay put, and under-rented units are never caught.

The point for the asset manager is that the portfolio demands a uniform and reproducible method — not a hundred independent judgement calls.

A consistent method across assets

Consistency does not come from assessing each tenancy more deeply, but from applying the same normalised framework to all of them. The core is to reduce every tenancy to the few parameters that actually drive the rent, and then estimate against comparable units on precisely those parameters.

The parameters that must be the same for everyone

For a portfolio estimate to hold together, every unit has to be described using the same variables:

• Geography at a granular level — not the postal code, but the immediate neighbourhood and, for commercial, location down to the street and frontage.
• Type and use — residential, retail, office, warehouse. Figures across different uses are not comparable.
• Area on the same definition — the most common place where consistency breaks down. A level per m² is only comparable if the area is measured the same way. Verify the area basis against BBR (the Buildings & Dwellings Register), and be aware of the pitfalls in BBR’s area concepts.
• Condition and fit-out level — the parameter that most often undermines a comparison. A newly refurbished tenancy cannot carry the level of one with deferred maintenance.
• Regulatory track — for residential, the track determines both method and ceiling. A market-based figure on a tenancy governed by cost-based rent or the value of the let is not too high, it is the wrong basis.

Normalisation before comparison

For commercial, the contract terms — non-termination periods, indexation, the split of maintenance obligations, rent-free periods — are what turn two identical figures per m² into very different economics. A portfolio estimate must therefore normalise the nominal rent to a comparable basis before the units are lined up against each other. We have walked through that normalisation step by step in the article on a realistic rent level per m² in commercial tenancies.

Rule of thumb: A portfolio estimate is only as good as the weakest area definition in the data set. Get the area consistent first — the rest follows.

Screen the portfolio: find the distance to the market

Once every unit has an estimated market rent level sitting alongside its actual rent, the screening becomes simple: sort by the distance between the two. That is the list that points to where the rent optimisation actually lies.

Three categories typically emerge:

• Clearly below the market. Actual rent sits well below the estimate. These are the candidates for an uplift — either on re-letting, through an adjustment where the rules allow it, or by bringing forward a planned refurbishment that moves the tenancy to a different level.
• At the level. Actual rent matches the estimate. These units require no action, but they are worth having documented, so the level can be defended if it is challenged.
• Above the market. Actual rent sits above the estimate. Here the point is not optimisation but risk: a tenancy above the market carries a vacancy risk on re-letting and, for residential, a possible repayment risk if the level is rejected.

The important thing is that the screening is not a conclusion, but a prioritisation list. It tells you where to dig deeper — not what the answer is. A large gap can reflect genuine under-renting, but it can also reflect a unit whose condition is poorer than the comparable units the estimate rests on. The prioritisation saves you from going through the whole portfolio by hand; it does not absolve you from validating the units that are actually going to be acted on.

Document the level per asset

A portfolio estimate is not an internal worksheet. The moment a rent is raised, an adjustment is demanded, or a unit feeds into a valuation, the level per asset has to be defensible — each one on its own.

That means the documentation has to be tied to the individual unit, not to the portfolio as a whole:

• The set of comparables per unit. Which comparable lettings sit behind the individual estimate, and how they differ. An assessment that cannot point to its basis falls at the first push-back.
• The normalisations. Which contract terms or differences in condition have been adjusted for, and how. It is the explanation for each deviation that makes an estimate robust.
• The currency. When the estimate was made, and whether it rests on a current market. A level from too long ago is no defence today.

This is precisely the documentation standard that a substantiation rewards. For a deeper look at how to build the basis so that it holds — including when deviations have to be explained — the walkthrough of how a rent is substantiated and tested with comparable leases is the natural next step.

At the same time, remember that the residential rules are detailed and vary with the age of the property, location and municipality. The applicable regulatory track for the individual property should always be verified in the current tenancy legislation or with the relevant municipality before an estimate is turned into an actual rent adjustment.

How Udlejningsvurdering does this systematically

What this article describes — reducing every tenancy to the same parameters, estimating against comparable units on the current market, screening the portfolio for the distance to the market, and documenting the level per asset — is exactly what Udlejningsvurdering (Rental valuation) in Arcili does in one consistent basis across assets. Instead of a hundred independent judgement calls, the same normalised method is applied to each unit, so the levels are comparable with one another and the estimate is reproducible when it has to be defended.

It does not replace the valuer’s or the asset manager’s professional judgement — it removes the hours spent gathering and normalising the basis for hundreds of units, so the assessment can concentrate on the assets that genuinely carry an uplift. To see how an entire portfolio is screened for under-rented units, start with Arcili or book a walkthrough.