With some serious security wiring around the property, say 3 geyser's, and things like underfloor heating or lots of downlights I reckon you'd easily get to 100Kwh/day - We are in a new (much smaller - 350sqm) house - built energy efficient from day one (insulation, LED lights, AA+ appliances, Heatpump etc) and in Winter very easy to hit 25kw/day. A single "normal" geyser would have pushed that to 35-45 per day.
It probably would not only save some cash, but result in a much smaller/less complex installation by first tackling some of the heavy energy usage first - a quick win is just to change good old downlights to LED versions - often a simple "screw out screw in" procedure - I can imagine in a house your size one could easily have 150+ downlights - @ 50W each - 7.5Kw/h just for lights - lets say 4 hours per day there's a 3rd of the 100Kw already. Some decent LED (6 or 6.5w) downlights will reduce it to 1Kw/h - or 4KW per day.
Other than lights, geysers are probably the worst (in smaller houses with much less lights the geyser is top of the list) - they are easily 3Kw each - so a couple of them will burn electricity very quickly. Your usage pattern should guide you around investigating some solar heating, or probably rather some heatpumps - which should save you around 60% of the usage on geysers alone - but this is more complex, requires plumbing etc etc - not always easy to retro-fit afterwards.
If you worked out the number of panels and batteries to generate and store for a 40Kw/day vs a 100Kw/day and the labour on installation the difference is huge.
My 2 cents worth..
