The temperature dependences of the electronic conductivity and the thermoelectric power are theoretically examined for the i-Al-Cu-Fe (1/1) approximant in comparison with both crystalline ω-Al7Cu2Fe and amorphous Al84Fe16. Our study is based on ab initio results for the spectral curves which are obtained by means of the linear muffin-tin orbitals (LMTO) method and the Kubo-Greenwood formula. Thermopowers are calculated after the Mott formula. We show that a realistic variety of thermopower curves versus temperature results from small shifts of the Fermi energy in a narrow resistivity peak. A simple model of the energy-dependent resistivity is suggested which supports the interpretation of the thermopower curves.