Wikipedia tells me super capacitor energy densities are around 0.01 MJ/kg (no idea if that's reasonable for consumer grade stuff) So to store 336 kJ you'd need 34 kg of super capacitor. Not nothin' but if you really want that cuppa right now you might go in for it. Electrolytic capacitors are more like 0.00001 MJ/kg, requiring 34 thousand kg. So... I won't be installing that under my sink.