I was searching the web and solar panel installation seemed very costly. Anyone any views as to rough payback period on solar water heating system.
The convenience factor as mentioned by InfoSeeker is usually a more compelling argument than ROI.
To calculate ROI, you need to work out what you're currently spending on heating water. That will depend on the number of people in the house, usage patterns and heat source.
Getting solar installed will cost from close to €3k and up, depending on panel size, tank size, and other factors.
Using an immersion element to heat water will consume a maximum of 3 units of electricity per hour, using a 10kW electric shower will use a maximum of 10 units of electricity per hour. Standard rate of electricity is currently 18c per unit.
If you take a rough guess of how long your shower runs for on an average day, and how long you have the immersion on for, you'll be able to work out a good indicative cost. How long before that reaches €3k? (If you use gas or oil to heat the water as part of your heating system, then your costs are likely to be lower again)
Keep in mind that there will be additional maintenance costs with a solar system, and parts will need to be replaced over time (check the warranty period of all components) and make a call on whether it makes sense. Only you can decide what the convenience factor is worth to you.
For me, ROI was going to be 10 years before any maintenance or replacement costs were included, so wasn't worth it.