Interview a few different solar panel installers before choosing the one for you. You've made a big investment by choosing solar panels, and you don't want any costly mistakes occurring during the installation. Find a team that knows their stuff. A company that has a track record that you can respect.
http://greenpowerscience.com/SOLARHOTWATER.html The pump does not need to be the 100 watt version. There are lower wattage pumps on the market.
Your solar energy system needs to be exposed to the sun at all times. Most homeowners have their solar panels installed on their roof but you could also have some panels installed on your front lawn. Do not hesitate to cut a few trees to avoid shadows and have a professional help you determine the best place for your panels.
You should never feel pressured to buy something, especially an expensive solar energy system. These types of salespeople are pretty common in this industry. You can tell them you'll be back later, and they should be fine with it. If they are persistent about making a deal now, tell them that the deal should be just as good in the future. Making decisions under pressure can be more costly later on.