need a new geyser - which is better, solar or gas?

Hi

We need to replace the current EOL (End Of Life) geyser in our granny flat, and I want to know what would be better (where funds are limited), a Gas geyser or a solar one?

A 10L/min geyser costs aprox R2k + R2.3K installation - the total quote with 2x 26KG gas cylinders was R4.5K, from these guys: (http://www.gasexperts.co.za/Water_Heater.htm)

Gas, AFAIK is rather expensive these days, but the geyser will always work if it's filled up.

So, even though we save electricity, we don't save money

Solar on the other hand will have a large cost upfront, but we don't need to refill any "solar cylinders"
But, how effective is solar? We're in JHB, which often sees dub 5 or sub-zero days in winter.

Any feedback / input from experience would be appreciated

I have a solar water heater in JHB - it's fitted with a backup electrical element for cloudy days so I never have no hot water (unless my brother takes one of his infamous 30 minute showers). A SWH should work fine in JHB winter because it's generally quite a sunny time of year.

Over a 20 year lifespan, methinks a gas unit will be significantly more expensive than a solar unit.

How many liter geyser is it, and what sort of usage does it get ?