Can I heat my house on solar energy only?

In theory yes, but taking expenses into account, solar energy should always be combined with another heat source, e.g. a wood burning boiler. Realistically, 50-70% of hot water and 25% of room heating can be provided by solar energy with water heating being the most viable application.

Is Energy demand for hot water not negligible ?

Hot water usually accounts for a substantial amount of your energy bill:

A central heating boiler may run quite efficient if it heats a house in winter - but not so, if it heats water in summer only. (It heats a large amount of 'dead' water first before transfering useful heat.) The balance looks worse again for electric water heating. Because of the low efficiency of steam power stations, electric water heating is most wasteful and expensive. (And this includes water heating in washing machines and dishwashers.)

Also, the energy demand for space heating can be dramatically reduced by good insulation and 'passive' solar building design (ask your architect about this). The demand for water heating can hardly be reduced - but solar energy can cover most of it!

 

Can I produce my own electricity and disconnect from the ESB?
You can, however keep in mind that a decent domestic electricity supply by wind and solar energy costs in the region of Euro 10 000.- (and this is only for moderate power demand; i.e. no electric heating or cooking).
Things look somewhat better if you have a steep mountain stream nearby - a small hydro system may cost from Euro 5000.- installed.
A much more interesting application for small electric systems is places with low power demand far from the grid, e.g. holiday houses on islands or remote mountain sites, remote monitoring equipment, navigational lights and transmitters or mobile power - in motor vehicles or boats.