One standard against another, decided.

An EPC rates how a building was designed and built; a DEC rates how much energy it actually consumed over the last 12 months.

SBEM is a simplified monthly calculation suitable for standard buildings; DSM simulates the building hour by hour and is required where systems are too complex for SBEM to represent.

An EPC is the certificate that measures a building; MEES is the regulation that says what that certificate must show before you can lawfully let it.

TM52 assesses overheating risk in non-domestic buildings; TM59 applies the same adaptive principles to residential buildings with stricter bedroom criteria.

Part L models only regulated energy to prove regulatory compliance; TM54 predicts total in-use energy including everything the occupier will actually pay for.

Section 63 is Scotland's regime, requiring an improvement Action Plan on sale or let of larger non-domestic buildings; MEES is the England and Wales regime, setting a minimum EPC band for lettability.

A standard EPC delivers the statutory rating and lodgement; EPC+ adds a costed uplift plan showing exactly what it would take to reach band B.

An Energy and Sustainability Statement satisfies planning policy before consent; Part L calculations satisfy building regulations before and after construction.

An asset rating scores the building as designed under standard conditions; an operational rating scores what the building actually consumed in use.

Retrofit is usually faster, cheaper and lower in embodied carbon; rebuild only wins where the existing fabric or floorplate cannot economically reach the target rating or the required rent.

Replacing gas heating with a heat pump almost always improves a commercial EPC rating, but only pays back where the fabric and emitter temperatures suit low-flow-temperature heating.

In-house teams can manage registers and evidence efficiently; accredited consultants are required to lodge certificates and are usually better value on complex modelling and portfolio strategy.