There should be quite a bit of information in a vendor’s proposal to you. The most important areas you need to feel confident in are explained below. These tips will help you evaluate and compare when purchasing a solar power system.


Do not automatically settle on the lowest price you’re offered. All vendors can quote you a “cost per watt” price. This is purely the price for all the equipment, labor and admin to install and complete your project. This is not in depth enough to make an informed comparison and to base your decision on. Why? This form of pricing has no relationship to performance. The solar vendor proposals you will be comparing should all have expected annual and lifetime production estimates. Look for a line item called “levelized cost of energy” or LCOE. This data point uses those production estimates and project costs to create your cost per solar kilowatt hour (kWh). At this point, consider the proposal with the lowest LCOE your best proposal.


Some of this will be driven by your personal choices. Do you prefer black panels with black frames, micro inverters, or optimizers over central inverters, have a preference on panel manufacturer’s country of origin, or prefer the highest-powered panels to keep the system footprint as small as possible? All these effect price which may end up increasing your LCOE but could be of higher priority to you. In all choices, you want to have quality equipment with proven reliability and good warranties.


The design should put panels on your most productive roof(s). This will generate the quickest payback, reduce your LCOE and generate the highest return on investment. If you are shown a design that has panels on a north facing roof, you need to ask the vendor to illustrate how the economics of that benefit you. If your design has panels on several roofs there will be more than one conduit (electric piping) to combine them. You should agree on where these will go. If you have your vendor route these conduit runs through your attic for aesthetic reasons, it will add some cost.


All solar contracts should have legal parameters that cover what constitutes your vendor’s obligations to your project execution, project change order process, payment schedule, warranty procedure and post project obligations. Some installations on tile roofs (esp. curved) cannot avoid breaking some existing tiles during installation. Be sure you have in writing how that will be addressed to your satisfaction.

So how do you know you’ve picked the best proposal?  It’s not a cut and dry choice. All these qualifiers need to be ones you have confidence in. They all affect your eventual LCOE value and must be weighed accordingly with your goals. As long as your LCOE is less than what your utility could be charging you during the life of the system, you’ll make a good financial decision. Those details are difficult for consumers to have confidence in and usually boil down to feelings of trust for the particular vendor and staff you interact with. That may be enough in some instances, but as we all know, information is power. The more you know, the smarter decisions you will make leading to better results. Soladvisor is here to help you with that.