Solar panel efficiency is the measure of how much energy a produced versus how much energy “hits” the module. The modules on the market right now have efficiencies between 8-23%. The more efficient a module is, the more power it produces per unit area. The higher efficiency ones are usually monocrystalline modules and are more expensive. The lowest efficiency, thin film, modules produce less power per unit area. They are followed by polycrystalline modules, which have efficiencies better than thin film, but not as good as the monocrystalline modules.
So does solar panel efficiency really matter? The answer depends on the budget and available roof space of the homeowner. For a homeowner with a smaller budget and abundant roof space, the best option would be to go for fairly efficient modules, like the polycrystalline kind. This way they would obtain cost-efficient modules to produce adequate power. For a homeowner with a large enough budget and less roof space, high efficiency monocrystalline modules are a good option. A user with no restrictions when it comes to roof space can easily opt for thin film as it performs better than the other modules during indirect sunlight periods and under high heat conditions.
Generally speaking, given a lot of space for installing these modules, we can use more lower efficiency modules to achieve the same amount of power desired at a better price point. The inverse is also true. With less roof space, the higher efficiency modules will make the best use of the space and produce the most amount of energy possible.