The energy relaxation of hot electrons in a strongly coupled, n-type GaAs/AlGaAs superlattice is measured by analysing the temperature and electric-field dependence of the interminiband absorption. Electrons are heated up by an electric-field pulse and the resulting change of the electron temperature is measured by monitoring the spectral change of the infrared absorption. The measured energy-loss rates are higher than predicted by a simple 3D model including acoustic and LO phonon emission. Other possible relaxation channels, such as folded acoustic phonons or coupled plasmon–phonon modes are discussed. An energy relaxation time can be extracted from the power balance and results to vary between 300 ps at 15 K and 20 ps at 48 K.