What is the best heating systems?

Depends what you mean by 'best'. The best in terms of comfort. The best in terms of energy efficiency. The best in terms of value for money.

Yes, a well designed hydronic system would probably be the most pleasant. Particularly for allergy sufferers, as unlike forced air systems, dust particles aren't blown all around the home.

The most energy efficient systems would usually be ductless mini-splits. While all other electric heating (like oil heaters, coil heaters, electric radiant heaters & electric underfloor heating) are the least energy efficient, & cost a bomb to run! The energy efficiency of a hydronic system depends on the heat source (& the quality of the design & install). Heat pump hydronic systems are the most energy efficient (though most costly install). Gas hydronic systems are a bit cheaper to install, but more costly to run.

Another advantage with reverse cycle splits (or ducted systems), is they can be used to heat or cool the home, so you won't have to install a second system. Though they are very energy hungry when cooling, compared to fans or evaporative cooling systems.

The facts that mini-splits are the most energy efficient & can be used for both heating & cooling usually makes them the best value. Multi-head splits may also fit this bill. Though for larger, complicated installs ducted reverse cycle may be better value (possibly a cheaper, less complicated install than splits in this case).

As for your other question about hydronic systems. These can be either underfloor heating or radiator panels. Radiators can obviously be installed in a house on stumps.

As for underfloor hydronics, yes it's most commonly laid in the slab in Australia, though this isn't the only method. I wouldn't say this is the best method of installation either (due to excessive thermal mass & heat losses to the ground). A better option is to lay specialised XPS panels on top of the sub floor, which the PEX hydronic tubing is attached to. A thin screed is usually poured on top of this. Another option, instead of the screed, is to use special aluminium plates, & top in timber. I'd do my research before choosing this last option, it's very specialised. This is because timber is an insulator, so not the obvious choice as part of a heating system. Also timber warps when heated, so specific timbers must be used.

Good point alexp79. Plus there's trench heaters, kinda like underfloor radiators.

Thanks so much for your advice.

Thanks Bels.

In the first instance the best heating system is the Sun. A house that is well designed can take advantage of the sun may require minimal heating or none at all.

Right now where we live it is -4°C outside and 17°C in our open plan area (slightly cooler in other rooms). Despite only having had BOM recorded average daily maximum of around 10°C, we have not had the heater on for three days. It was 26°C inside yesterday and I had to slightly open some windows and put on shorts.