We've been looking into this as well as we are building a new house. The local council has now made it a new rule that any new dwellings either have to have a gas boiler, heat pump or solar for hot water.

We have opted for solar as there isn't mains gas here.

A few things we have found out, firstly go for a roof tank as then you don't need an electric pump to pump the water around - for myself personally if another cyclone hits us we will still have hot water.

Secondly the better type to have is a closed system where it has a gel running around the panels and then the heat is transferred to around the water tank instead of having the water running around the panels themselves. This way you won't get the panels blocking up if the water quality isn't that great.

Quotes we have so far have been from Solarhart although I will be going elsewhere before we buy for others.

302J Solarhart $3325.00 do it yourself cost
302J Solarhart $3793.00 which includes a 'plonk' on fee where they come and assemble it and plonk it on your roof ready for the plumber to fit.
302L Solarhart $3205.00 includes plonk on

The 302J is the closed in system and the 302L is an open system.

Going for the "tank on the roof" option places all your eggs in the one basket so to speak. If the unit packs up [prior to the fitting of sacrificial anodes Solarhart systems had a problem of rotting out within 10 yrs] the whole thing needs replacing. Other minus points are that with the added weight of the tank + panels + water on the roof the roof requires extra bracing at added cost. For us personally having 2 nice neat unobtrusive panels on the roof was also a bonus.
The plus point is as you say the hot water is high up on the roof so in the case of a cyclone, if you still have a roof, you'll still have hot water. You also don't need the circ pump.
Another point to remember is that in order to work efficiently the solar panels do need cleaning periodically, I'm not game enough to climb up & do mine

The extra cost for the roof trusses was minimal when we costed it all up (only a couple 100 bucks for an extra weight of 1 tonne spread over a certain area). I have to say I hate the look of them on a roof but for us the no electricity thing was a major factor as to what we decided to do. I didn't realise all of this until we started to look into it so I'm not saying it is the right way to go just for us it doesn't seem much point having solar if we can't use it unless there is electricity.

I know people with ground tanks having the same sort of problems due to them using a stupid plastic part joining the downpipe to the panel which in the Queensland sun gets brittle and breaks after a very short time causing a leak. One person I know changes this part once a year. Hence the not necessarily going with Solarhart

Blinking gutted they have changed the rules recently and what seems in a stupid manner as they still allow units to fit an electric water heater. So basically as a family we would use the one boiler but on the same block of land on the estate where there is 10 units built using 10 times the amount than we can generate...so much for the environment argument

We didn't like the look of the heat pump option just thinking how all the humid salty air being dragged into a system wouldn't do it much good surely??? Plus they haven't been around long enough to know what they are like over longer periods of time.

We have the solar hot tank on the ground. If the power goes we lose the pump from the rain water tank so have no water at all - hot or cold.

A generator is probably the only solution. We used to have one in the UK as we had loads of power cuts there. (Needed for fridge/freezer, cooking, heating..)

However, we are now seriously contemplating PV panels.........