SBEM Level 3 vs Level 4 vs DSM: Which Commercial EPC Do You Need?

Level 3 and Level 4 are both SBEM assessments: Level 3 is for smaller, simple buildings, broadly under 250 square metres, and Level 4 for larger or more complex buildings and all new-build commercial. DSM is a separate, Level 5 assessment using Dynamic Simulation Modelling for the most complex buildings that SBEM cannot model reliably. Your building sets the level, not you, and getting it right matters for both accuracy and cost.

There is a lot of confusion on this, including a persistent error worth clearing up straight away: DSM is not Level 4. A Level 4 assessment is still SBEM. DSM is Level 5. If a quote or an article tells you your building needs “a Level 4 DSM”, something is muddled. This guide explains what each level is, what pushes a building from one to the next, and how the level affects your fee.

Two engines, three levels

Every commercial EPC in England and Wales is produced with one of two calculation engines. The engine, and within SBEM the level, is determined by the building.

• SBEM, the Simplified Building Energy Model, is the government’s standard engine and covers the large majority of commercial buildings. It is used at two levels: Level 3 and Level 4.
• DSM, Dynamic Simulation Modelling, is a more sophisticated engine for buildings SBEM cannot model reliably. A DSM assessment is a Level 5.

Level	Engine	Typical building	What defines it
Level 3	SBEM	Small shop, cafe, single office suite (broadly under 250 sqm)	Simple, small, straightforward services
Level 4	SBEM	Whole office floors, warehouses, pubs, hotels, care homes; all new-build commercial	Larger, or more involved heating/cooling/ventilation and controls
Level 5	DSM	Buildings with atria, automated blinds, advanced HVAC	Complexity SBEM cannot model reliably

The single most important thing to take from that table: Level 3 and Level 4 are the same software applied to different buildings. The jump to DSM at Level 5 is a genuine change of method, not just a bigger version of SBEM.

Level 3: the simple SBEM assessment

Level 3 covers the smaller, simpler end of the commercial stock, a single shop, a cafe, a small self-contained office suite, broadly under 250 square metres with straightforward heating and services. This is the most common assessment by volume, because relets, sublets and sales of small units happen constantly.

If your building is a single-zone unit with, say, a simple gas or electric heating system and no mechanical cooling or ventilation to speak of, it is very likely a Level 3 job. It is the quickest and cheapest assessment, but “cheapest” still means an accredited assessor and a proper survey, a wrong rating on a small unit is just as damaging in a transaction as on a large one.

Level 4: the complex SBEM assessment

Level 4 is still SBEM, but for buildings that are larger or have more going on. It covers whole office floors and multi-zone offices with air conditioning, warehouses and industrial units, pubs, restaurants, hotels, care homes, surgeries and clinics, and, importantly, all new-build commercial regardless of size.

What pushes a building from Level 3 to Level 4 is not a single measurement but a combination: greater floor area, multiple thermal zones, air conditioning, mechanical ventilation, and more sophisticated heating, cooling and control systems. A building with several zones and a couple of separate services is a Level 4 assessment even if its floor area is modest, and any new commercial building is Level 4 by default.

Because the assessor has to survey and model every zone and every service, a Level 4 assessment takes longer and costs more than a Level 3. That is a reflection of the building, not an upsell, and it is the level most offices, warehouses, hospitality and care premises fall into.

Level 5 (DSM): for the buildings SBEM can’t model

Some buildings cannot be modelled reliably by SBEM at all. Large atria, automated blind systems, advanced or dynamically-controlled HVAC, the kinds of features found in landmark offices, complex mixed-use developments and unusual industrial buildings, need Dynamic Simulation Modelling, which is a Level 5 assessment using specialist software.

DSM is a genuinely different, more involved piece of work, so it is the most expensive route. The good news is that most owners never need it: the large majority of commercial buildings are handled at SBEM Level 3 or Level 4. If your building has the kind of complex, dynamically-controlled systems that push it to DSM, that will be clear at survey, and an assessor accredited to Level 5 is required to carry it out.

How the level affects your fee

Because the assessment level tracks the complexity of the building, it is also the biggest single step in the price.

Level	Relative effort	Effect on fee
Level 3 (SBEM)	Lowest, single or few zones	Lowest cost
Level 4 (SBEM)	Higher, every zone and service modelled	Moderate to high cost
Level 5 (DSM)	Highest, specialist dynamic modelling	Highest cost

The level is not the only price driver, floor area, the number of systems, the number of zones and site access all feed in, but it is the one that most visibly separates a few-hundred-pound job from a four-figure one. We set out the full picture in our commercial EPC cost guide and our guide on how much a commercial EPC costs in 2026.

Who is qualified to do which level

This is where accreditation matters. A legally valid commercial EPC must be produced by an accredited Non-Domestic Energy Assessor, and the assessor must be qualified to the level your building requires. An assessor accredited only to Level 3 cannot lawfully produce a Level 4 or Level 5 certificate.

Accreditation is held through a government-approved scheme such as Elmhurst, Stroma/NAPIT, Quidos or ECMK. You can read more about assessment for non-domestic buildings on GOV.UK{rel=“noopener”}, and you can check any existing certificate on the find an energy certificate service{rel=“noopener”}. The practical implication is simple: make sure whoever assesses your building is accredited to the correct level for it, or the certificate may not stand up when you rely on it.

Common questions

Is DSM better than SBEM? Should I ask for it?

No, and no. DSM is not a premium upgrade you opt into for a better rating, it is the required method for a narrow set of complex buildings that SBEM cannot model reliably. For the large majority of commercial buildings, SBEM at Level 3 or Level 4 is the correct and only appropriate method, and asking for DSM on a building that does not need it just adds cost for no benefit. The right method is the one your building requires.

My building is about 300 sqm. Is that Level 3 or Level 4?

It depends on more than floor area. The rough 250 sqm guideline is a starting point, not a hard cut-off. A 300 sqm single-zone unit with simple heating may still sit at Level 3, while a 200 sqm building with air conditioning, several zones and mechanical ventilation is a Level 4 job. And if it is a new-build, it is Level 4 regardless. The assessor confirms the level at survey based on the whole picture, size, zones and services together.

Not sure which level your building needs?

The honest answer for most owners is that the level becomes clear once someone who assesses commercial buildings for a living looks at the size, the zones and the services. We will tell you which level applies before any survey, so there are no surprises on the invoice. To get a firm quote at the correct assessment level for your building, request a free commercial EPC quote and we will confirm the right route first.