For instance, there could be agreement that renewables constitute EPPs based on the source of energy (i.e. the resource) rather than on the use of the products, as their categorization is not so much based on the specific category of technologies (e.g. electricity-generating motors, power converters or inverters) as it is on the source of the power (e.g. biofuels, low-head hydro, solar, wind or geothermal). Other goods using a particular source of energy could be classified as a single source within a category (e.g. electric cars or trains which fall under HS 8703 or HS 8601). However, the majority of these goods owe their environmental performance to a combination of features, and can only be definitively identified through testing.