Check The Size Of Your Tank
A family of 3 to 4 people would usually require at least a 250-litre tank to sufficiently provide enough hot water to the family. Less than 250 litres just won’t cut it for over 3 people in the middle of winter. If you have a smaller tank that’s not supplying enough hot water to your family, upgrading to a bigger hot water system tank should be a priority.
Also, if you have a small tank running on an off-peak tariff, this could lead to insufficient hot water since it only heats once in an evening and not when it really needs to.