There are two basic types of photovoltaic modules:

Crystalline modules (mono and poly) and thin film modules. Crystalline modules are based on silicon cells and have a high efficiency. They are, however, more expensive than thin film modules. Thin film modules contain a thin amorphous layer of silicon or alternative materials (such as CdTe). The efficiency of thin film modules is lower; they are, however, less cost intensive. Thin film systems are especially suited for installation on large roof areas. If roof space is at a minimum, a crystalline module with its high efficiency might prove more suitable.