YSK All 1500W heaters put out the exact same amount of heat, and consume the exact same amount of electricity, regardless of physical size, or the properties of the heating element.
from /r/YouShouldKnow
YSK 1500Wのヒーターは、大きさや発熱体の特性に関わらず、すべて同じ熱量を出し、同じ電力を消費します。