The success of a solar thermal or photovoltaic system depends a lot on details. So, be aware, when choosing a contractor.
Take time in choosing the contractor. His know-how is important.
Larger manufacturers work with local installers and dealers, and this is a way of entering into contact with solar professionals in your area...
When assessing proposals, make sure that the different contractors are bidding on comparable services and products. Comparing proposals may not be straightforward, and it's much more than just comparing prices.
PV photovoltaic panels (for solar electricity) are manufactured by large multinational companies; even solar thermal panels are now mostly manufactured by large corporations...
New Asian players are shaking the market, and there are worrying news about sub-standard materials used in solar panels, or poor wire cable insulation and poor workmanship.
Here is a small list of manufacturers associated with PV products:
Sharp Solar (Japan),
Sanyo Solar (Japan),
Schott Solar (Germany),
Solar World (Germany),
Kaco (Germany, solar inverters),
OutBack (USA, solar inverters),
Mastervolt (USA, solar inverters),
Unirac (solar mounting systems),
Zomeworks (USA, solar trackers).
Solar thermal products and Companies
Solar thermal products involve solar water heating, solar pool heating, solar space heating and solar cooling, and contrary to what happens with solar electricity (photovoltaics) the market involves a large number of relatively small companies.