I want to install a PV system on my roof but I am not sure about the static?
The load of photovoltaic modules including the mounting syste is typically around 15 to 20 kg per sqm (3.0 - 4.5 lb per sq ft).
Installing a PV system on a house in good conditions with a pitched roof (modules are installed parallel to the roof) usually doesn't cause any problem for the roof static.
However, keep in mind in case something happens the insurance could ask about an expert's report. So if you have any doubts consult a specialist (e.g. structural engineer, technical expert), in order to guarantee the loading capacity of your roof structure.
If you install your PV system on a flat roof (on a flat roof modules are installed not parallel to the roof, but with a tilt angle) you need to consider additional loading conditions from wind and maybe snow.