Understanding the energy performance certificate: HWB, fGEE and what the rating actually means
No property advert without an energy performance certificate — but what do the figures mean? A guide for buyers, tenants and owners.
No property advert without an energy performance certificate: for years now, sellers and landlords have been required to state the heating requirements and overall energy efficiency of their property, and the certificate must be available at the time of handover. Most prospective buyers skim over the figures without really understanding what they mean. Yet these figures reveal a great deal about a property’s running costs, the need for renovation and its future value.
This article is a guide — for buyers who want to know what they’re getting into, and for owners who want to understand what their property certificate reveals about their home.
Why the ID card exists
The energy performance certificate is a European initiative, implemented in Austria under the Energy Performance Certificate Act. It is designed to make buildings comparable, just like the label on a fridge: a scale from A++ to G, a few key figures, and a colour. It is valid for ten years and must be issued by an authorised body — civil engineers, building contractors or energy consultants.
Anyone who advertises or sells goods without a certificate risks an administrative fine. More important than the fine, however, is the effect: without a certificate, the buyer is missing a piece of information they have come to expect over the years, and that erodes trust and, ultimately, the price.
HWB — heating demand
The HWB indicates how much heat a building requires per square metre of gross floor area per year to maintain room temperature — in kilowatt-hours. It describes the building envelope: walls, windows, roof and basement ceiling. A Viennese ‘Gründerzeit’ building without thermal refurbishment typically exceeds 100, often by a significant margin; a modern new-build is below 30, whilst a passive house is around 10.
The HWB is stated for the reference location, so that buildings in Vienna and Tyrol can be compared, and also for the actual location. The reference value is used for the classification. Anyone wishing to estimate operating costs should use the location-specific value — and bear in mind that both figures are based on a calculation model, not a meter reading.
fGEE — the overall energy efficiency factor
The fGEE assesses not only the building envelope but also the building services: heating, hot water, ventilation and cooling. It compares the building’s energy consumption with that of a reference building based on 2007 standards. A value of 1.0 corresponds to this standard; the lower the figure, the more efficient the interaction between the building envelope and the technical systems.
This explains why an older building fitted with a new heat pump or connected to district heating can achieve a significantly better fGEE than its HWB figure would suggest — and why a new-build with an old gas boiler performs worse than its façade would lead one to expect. If you consider both figures together, you can understand the building.
Other key figures
The certificate also states the primary energy demand, which takes into account the energy source — electricity, gas, district heating, wood — and the CO₂ emissions. These figures will become more important in the coming years, as they are linked to subsidies and regulatory requirements. A house heated by gas is assessed differently here from one with district heating, even if both have the same building envelope.
And then there’s the class: the letter that everyone reads. It is derived from the HWB and serves as a rough guide — nothing more. Two properties in class D can differ significantly in terms of actual costs.
What the ID card doesn’t say
The energy performance certificate is based on standard values: a room temperature, a set of user behaviours, and a climate. Those who live at 24 degrees and ventilate in winter use more energy; those with a flat in the centre of the building use less than those in a corner flat. The certificate says nothing about the condition of the heating system, nothing about its maintenance status, and nothing about damp or draughts. It does not replace a viewing — it complements it.
For sellers and buyers
It’s worth homeowners taking a look before selling: a recent, good energy performance certificate is a selling point, whilst a poor one is a point of negotiation. Sometimes, a new energy performance certificate is all it takes following a refurbishment carried out years ago — the old one doesn’t reflect this. For buyers, the certificate acts as an early warning system: a rating of F or G indicates a need for refurbishment, and this should be factored into the purchase price.
For every property, we show both key figures, complete with a rating, and are happy to explain what they mean for your specific decision — whether you’re a buyer looking to estimate running costs over the next twenty years, or an owner wanting to know what your house is worth.
