This will depend on the company you work for. If you work for a solar panel manufacturer, you would be working on designing the panels, electronics, power distribution, mounting, etc. This would be exciting work requiring in depth technical background.
If you are working for a local solar installation company, which you might see advertised on local job sites, this will be a bit different. Sometimes the term "engineer" is used a little loosely in these types of job descriptions, so make sure to ask about the specific duties of any job you see posted. This would likely involve sales to homeowners or businesses, quoting installation cost/time/equipment to support sales, or perhaps specifying the necessary equipment and installation for larger and more complex jobs.