Context : Hot subdwarfs are helium burning objects in late stages of their evolution .
These subluminous stars can develop winds driven by light absorption in the lines of heavier elements .
The wind strength depends on chemical composition which can significantly vary from star to star .

Aims : We aim to understand the influence of metallicity on the strength of the winds of the hot hydrogen-rich subdwarfs HD 49798 and BD+18 ^ { \circ } 2647 .

Methods : We used high-resolution UV and optical spectra to derive stellar parameters and abundances using the TLUSTY and SYNSPEC codes .
For derived stellar parameters , we predicted wind structure ( including mass-loss rates and terminal velocities ) with our METUJE code .

Results : We derived effective temperature T _ { \text { eff } } = 45 900 K and mass M = 1.46 M _ { \odot } for HD 49798 and T _ { \text { eff } } = 73 000 K and M = 0.38 M _ { \odot } for BD+18 ^ { \circ } 2647 .
The derived surface abundances can be interpreted as a result of interplay between stellar evolution and diffusion .
The subdwarf HD 49798 has a strong wind that does not allow for chemical separation and consequently the star shows solar chemical composition modified by hydrogen burning .
On the other hand , we did not find any wind in BD+18 ^ { \circ } 2647 and its abundances are therefore most likely affected by radiative diffusion .
Accurate abundances do not lead to a significant modification of wind mass-loss rate for HD 49798 , because the increase of the contribution of iron and nickel to the radiative force is compensated by the decrease of the radiative force due to other elements .
The resulting wind mass-loss rate \dot { M } = 2.1 \times 10 ^ { -9 } M _ { \odot } \text { yr } ^ { -1 } predicts an X-ray light curve during the eclipse which closely agrees with observations .
On the other hand , the absence of the wind in BD+18 ^ { \circ } 2647 for accurate abundances is a result of its peculiar chemical composition .

Conclusions : Wind models with accurate abundances provide more reliable wind parameters , but the influence of abundances on the wind parameters is limited in many cases .