1. The two certificates and how they differ
The difference lies in their underlying data, and everything else follows from it. One rests on calculation, the other on measurement.
| ETA, energy performance value | KEK, weighted specific energy use | |
|---|---|---|
| Prepared for | buildings being designed, i.e. new and substantially reconstructed | existing buildings |
| Basis | calculation | actual consumption data |
| Validity | 2 years from the occupancy permit | 10 years |
| Answers the question | how efficiently the building was designed | how much is actually consumed in it |
The difference in validity is fivefold. It is not arbitrary: a calculation describes an intention that construction may alter, a measurement describes what has already happened.
2. What each measures
The measured content is the same in both cases, which often goes unnoticed. The difference lies in where the data come from.
Three components enter the account either way: energy use for indoor climate, domestic hot water heating, and the use of household and electrical appliances. Together they make up the whole account.
The difference therefore lies not in what is measured but in whether it is calculated or measured. The same building can carry two different figures without either being wrong.
3. Why they are confused
Three reasons, all understandable, and one consequence that is not. The consequence concerns a wrong comparison.
| Reason | Explanation |
|---|---|
| Both are called an energy certificate | everyday speech does not distinguish |
| Both carry an energy class | the classes look identical |
| Both sit in the building register | in the same format |
The consequence of the confusion is an expectation that the calculated certificate predicts future bills, which it does not, as covered by the article on why calculation and reality diverge. According to professional sources this expectation has produced disappointment and disputes, so the difference has to be spelled out to the client beforehand rather than afterwards.
4. Where the certificates are held
One channel, and it ties this guide to the building permit guide. The certificate is filed through the building register.
Energy certificates are issued only through the building register, and the register is public, which makes the certificates accessible to everyone. A buyer can therefore check a building's energy class before making an offer, without asking the seller.
5. Why the distinction is practical
Three situations in which the wrong certificate means the wrong answer. They concern a sale, a loan and a procedure.
| Situation | Which certificate counts |
|---|---|
| Buying a new building | ETA, which describes the designed level |
| Buying an old building | KEK, which describes actual consumption |
| Planning a reconstruction | both: the current actual and the intended calculated |
The third situation is the most common and the most often mishandled. Looking only at the current KEK tells you nothing about whether the intended solution meets the requirement; looking only at the intended ETA tells you nothing about the real gain.
Summary and four practical rules
The calculated certificate ETA is prepared for new and substantially reconstructed buildings and is valid for two years from the occupancy permit; the KEK, based on actual data, is prepared for existing buildings and is valid for ten years. The measured content is the same in both, namely indoor climate, domestic hot water and household and electrical appliances, and the difference lies only in whether it is calculated or measured. Certificates are issued solely through the building register and are publicly accessible.
Four rules: tell the client plainly that the calculated certificate does not predict bills. Check which certificate counts in the situation at hand before interpreting a class. When planning a reconstruction, take both into account. Use the register's public view before making an offer, since it is free and fast.
This article offers professional orientation as at the date of verification. It replaces neither the regulations in force nor the assessment of a competent specialist.