TRAPPIST-1 e is notable as being remarkably Earth-like in many ways. It is slightly smaller and less massive than Earth (about nine-tenths of Earth'sdiameter) which strongly implies that it is a rocky planet. Because the TRAPPIST-1 star puts out significantly less energy than the Sun, its habitable zone - the zone in which liquid water can exist - lies much closer to the star, and TRAPPIST-1 e orbits confortably within this zone. The presence of oceans on the planet, then, while not confirmed, is at least plausible.
The surface temperature of the planet is hard to calculate because the details of its atmosphere (if indeed it has an atmosphere) are not known, but it is at least possible that the planet's surface might be temperate and Earth-like. All these factors combine to give TRAPPIST-1 e a very high Earth Similarity Index (ESI) value of 0.95, though the volatile nature of its star, and the proximity of its orbit, mean that it may be less habitable than this figure suggests.