Opting for the lower wattage panels for your residential installation can save as much as 50% on the generation costs of your system. When considering what size solar panels to install for your home, you also need to consider the generation cost. This is the cost per watt incurred, and you. The capacity and ability of solar panels to generate electricity are relative to how efficient they are at generating power using the available solar energy. Modern-day solar panels. Low-wattage solar panels can have as little as 3W power generation, and these are typically used to trickle charge batteries that power small low voltage devices. These. This is going to depend on the application. For home or residential systems, solar panels are usually rated at between 290W and 320W, but you can get panels of 500W or more if.