Though solar energy‐driven steam generation is promising for cleaning water, the water evaporation efficiency has to be enhanced further. Herein, 3D reduced graphene oxide (RGO) decorated cellulose acetate filter (RGF) evaporators are fabricated by immersing the porous cellulose acetate filters (CFs) in a suspension of graphene oxide, followed by drying and chemical reduction for efficient solar steam generation. The RGO sheets can absorb solar light and convert solar energy to thermal energy, while the hydrophilic and porous CFs with lots of vertical channels are responsible for transporting water to the top evaporation surfaces and accommodating the RGO sheets. In addition to gaining thermal energy from direct solar energy absorption and conversion, the sidewall of the RGF evaporator can also gain additional thermal energy from the surrounding environment as long as the sidewall temperature of the RGF evaporator is lower than the surrounding environment temperature as a result of the cooling effect of the evaporation. Driven by both solar energy and environmental energy, the RGF evaporator achieves a high water generation rate of ≈2.81 kg m−2 h−1 with an energy conversion efficiency of ≈130.2%, and high efficiencies in cleaning seawater and wastewater are also demonstrated.