Most commercial buildings in Spain already hold more energy data than anyone uses. Energy performance certificates, utility bills, meter data and building management system logs all exist, but they rarely sit in one place or answer the question an owner actually needs answered: where is the energy going, and what is worth fixing first. This article sets out a step by step engineering method that turns those scattered sources into a ranked list of measures. | Step 1: establish the legal baseline. Before any measurement, confirm which obligations already apply to the building and the organisation. Two Spanish instruments matter most. | Energy performance certificate (Real Decreto 390/2021). Required when a building is sold or let to a new tenant, and for buildings over 500 m² in uses such as offices, retail, healthcare and hospitality. The certificate is valid for 10 years, or 5 years where the rating is G, and must be registered with the regional authority. Buildings in scope must display the energy label. | Mandatory energy audit (Real Decreto 56/2016). Large companies must carry out an energy audit every four years covering at least 85 per cent of their total energy consumption, unless they operate a certified energy or environmental management system such as ISO 50001 or EMAS. | The certificate describes the building on paper; the audit describes how it is actually used. Read them together. A large gap between the certified rating and metered consumption is the first finding of any investigation. | Step 2: collect the measured data. Gather at least two full years of consumption so that seasonal patterns are visible. In Spain most supplies have hourly consumption data available from the distribution company, which is far more useful than monthly invoices because it shows when energy is used, not just how much. Add any sub-metering, BMS trend logs for air handling units, chillers and boilers, and occupancy information such as access control counts. | Step 3: walk the building. Data shows symptoms; a site survey finds causes. A structured walk-through should check: | HVAC time schedules against real opening hours, including weekends and holidays. | Setpoints and dead bands, and whether heating and cooling run at the same time in neighbouring zones. | Ventilation rates against actual occupancy. | Lighting controls, especially in car parks, stores and circulation areas. | The condition of insulation, glazing and solar shading on the most exposed façades. | Step 4: build a normalised baseline. Consumption has to be compared like for like. Normalise heating and cooling energy against degree days for the location, and adjust for changes in occupancy or opening hours. Without this step, a mild winter can look like a successful efficiency project, and a hot summer can hide a real improvement. | Step 5: rank the measures. List every candidate measure with its estimated saving, cost and payback, and separate them into three groups: operational changes that cost almost nothing (schedules, setpoints), control upgrades (BMS logic, sensors, variable speed drives) and capital works (plant replacement, envelope). Operational changes come first because they are fast and they also clean up the baseline for the larger decisions. | Agree in advance how savings will be verified. The International Performance Measurement and Verification Protocol (IPMVP) gives a recognised framework, and it protects both the owner and the contractor when results are reviewed. | Step 6: plan against the EPBD recast. The recast Energy Performance of Buildings Directive (Directive (EU) 2024/1275) had to be transposed by 29 May 2026. For non-residential buildings it introduces minimum energy performance standards: the worst performing buildings must improve so that they sit below the 16 per cent threshold of the national stock from 2030 and the 26 per cent threshold from 2033. A building that is already measured, normalised and ranked can plan its renovation steps against those dates instead of reacting to them. | Where to go next. Our EPBD 2024 compliance guide explains the directive in detail, and the free EPBD compliance checker gives a first indication of where a building stands. For an engineering review of a specific building, contact our team.