Not even close. Volume is basically irrelevant, it's surface area that matters. Double the dimensions of a tank and the volume cubes, but the surface area only squares. If 10 liters takes 10 watts to keep at a set temp, double the dimensions and you'll have an 80 liter tank that takes 40 watts to keep at temp or 1 watt per 2 liters. Triple the dimensions 270 liters that takes 90 watts, 1 watt per 3 liters.