SunPower has announced a new series of solar panels with 21.5% efficiency, about 44% more than the 15% efficient panels typically installed. While this does not mean choosing SunPower will get you cheaper electricity per kWh (it is a free marketplace after all), it does have some interesting knock on effects.
If your panels produce 44% more kWh than current standard installations, to get the same amount of kWh you need 30% fewer panels. For installers, this means costs associated with panel installation like labor and racking should also be 30% lower. This is a significant cost reduction and points out how increased panel efficiency will drive down installation costs.