Guarantees of Origin and RECS certificates fulfil the same function, and are of the same quality. Where they differ is that a Guarantee of Origin is required under the EU "RES Directive" (201/77/EC and its successor, 2009/28/EC), which are obligatory on all Member States of the European Union; whereas RECS certificates are issued as a voluntary initiative by energy companies.

Although it is possible for Guarantees of Origin to be printed, the EECS standard does not support this: all EECS Guarantees of Origin and RECS certificates are electronic. The reasons for this are given elsewhere in these FAQ ("Why should certificates be electronic?" and "Can you print EECS certificates?").

Countries where the certificate issuer does not provide electronic and transferable Guarantees of Origin may adopt voluntary RECS certificates. Alternatively, they can contract with a service organisation to use Guarantees of Origin as a basis for issuing EECS Guarantees of Origin, while preventing the original Guarantees of Origin from being reused.

If this sounds a little confusing, think of it this way. Gold assures the value of a currency in a similar way that Guarantees of Origin assures the value of an EECS Guarantee of Origin. You keep the gold (and the Guarantee of Origin) in the bank vault; and you trade the currency (and the EECS Guarantee of Origin).