Me and my flatmate are very conflicted on this. I believe it's actually using more electricity when you constantly switch it on and off, and he believes switching it off works.
We've only got a 100l geyser, and once switched off it cools down rather fast, so it has to reheat from scratch when you want to switch it back on again. I've monitored it and when it's been turned off for the day it easily consumes between 3 and 5 units to heat back up again. Leaving it running during the day seems to have it only use about 1 - 2 units of electricity to keep itself heated.
Our electricity consumption per day used to be about 15 units when we switched the geyser on and off, then last week I started leaving the geyser running and we only used about 10 units a day. My flatmate insists this is pure coincidence and he and his father fights with me because I want to 'waste money by leaving the geyser on'. This really sucks because their solution to 'save' money seems to be doing nothing more than costing us money.
Even if it does actually save money, I wouldn't think it would be more than R50 a month, which is insignificant considering what an inconvenience it is to have your geyser off the whole day. If I want warm water, there should be warm water. I hate having to get up at 6 in the morning to switch the geyser on just so I can be sure there will be warm water for a shower so I can be at class at 8.
Has anybody else tried both switching it off and leaving it on and have you noticed any 'significant' savings?