Because installing a solar energy system is a very large investment you should interview at least 3 professional solar providers before making your decision.  The first question you should ask is how long they have been in business and how many solar energy projects they have installed.  Find out if they are certified to install solar electricity or solar thermal.  Ask to see some pictures of completed projects and call some of their references. 

To complete the bid each provider will ask you some questions about your energy use and may need to see some of your utility bills.  They will conduct a site assessment to determine the location, type, and size of solar energy system that would best suit your needs. 

You will want to ask the providers these questions

How much energy the system will product? 

What portion of your energy use will be offset annually? 

Is there a way to measure the production data?

How much money will you save each year?

What is the total cost to install the system?

What incentives are available to reduce the costs?

Who will handle the paperwork?

How can you finance the project?

Is your work covered under a warranty?

Is the system covered under a warranty?

Will you be pulling all necessary permits?

What maintenance is necessary?

When will the installation begin and end?

Do you work with the electrical utility to complete the grid interconnection? 

Is there a fee for this service?

Be sure each written bid includes the system size and type, energy production, maintenance requirements, and installed cost.  Carefully compare the bids.  It isn't always a good idea to hire the cheapest installer.  Consider their experience and qualifications.