When is a "discount" a discount?

Discount solar panels for residential solar systems are fairly plentiful. However, you get what you pay for. Depending on the type of panel (PV or Solar Thermal), its technology (flat plate, evacuated tube, monocrystalline silicon, polycrystalline silicon, etc.) and the reason for it being discounted, a panel offering might be a good deal.....or it might not. It's not dollar cost that matters so much as dollar cost per watt or dollar cost per BTU that the panel can capture and convert into useful energy. We explain below.

Market Value

It's important to understand the inherent value of the different types of panels. For instance, , monocrystalline silicon type PV panels are more expensive to manufacture than thin film panels, so in the general market place they most times command a higher price. The newer high voltage (65vdc) panels are more expensive than older generation low voltage (12vdc) panels, but they're much more efficient for line transmission of power. So all things being equal, they also will command a higher price. Given that there are so many different technologies, how do you coherently evaluate comparative value?

The best way to determine real value is by examining a panels cost or price on the basis of dollars per watt or BTU (for Solar Thermal). This measure normalizes value across various technologies and applications. Why? Well, as in the case of PV panels for instance, a watt is always a watt. No matter how you produce it, no matter what technology is used, the output of a PV panel is always a matter of volts, amps and conversion efficiency (the rate at which it converts 100 watts of sunlight into electrical watts). If the PV technology for a panel has a low conversion efficiency its "discounted" cost may actually extend into a more expensive cost structure when applied to an array configuration, than a more expensive panel. In other words, a per unit discount may be useless when matched against the requirements and specifications of the system (see below).

Applied Value

Applied value, that is value derived in terms of a specific application, is governed by system requirements. For example, panel A costs $1500. Panel B costs $2000. So panel A is cheaper. Right? Maybe. It depends on how many Panel A units would be needed to fulfill the system output requirements. As long as a single unit is all that's needed then all is well. However consider, if panel A has a conversion efficiency (CE) of 8% and panel B has a CE of 18%, then all other things being equal, where system requirements would call for 2 or more units of panel A, a single unit of panel B would save at least $1000 dollars and still produce power to spare. This means that it's very important to understand your application because the financial merits of a "discount" might disappear altogether when system requirements are factored into the discount and value equations. With this information in mind, evaluating and purchasing discount solar panels becomes much more of a "cut and dried" task.

Be that as it may, there are ways to acquire solar panels so cheaply that the discount can easily overcome the applied value threshold. Depending on the application, building your own solar panel(s) is quite a viable alternative for gaining a discount.