It is always best to install your solar panels where they will get the most sunlight each day. It is important to check regularly for trees that may be overshadowing solar panels due to growth.
Don't assume that you have to live in the desert to use solar panels on your roof. If your roof expanse gets a minimum of five hours of direct sunlight on an average day, there is likely a solar panel installation that can generate electricity for your home or building.
Get your financial figures right before deciding on a solar system. You need to weigh the cost of the system against how much energy it will save you. Take the cost of the system and multiply it by its' lifespan. Now figure out how much energy you will use in that lifespan to determine if it is right for you.