Most houses in Australia have a single electrical system that may be broken up into two or more circuits. Usually there are separate circuts for light and power. Most of these circuits are 240 volt AC or alternating current. Many lighting fixtures are in fact 12 volt DC (Direct Current) however these light fittings have either an inbuilt transformer or a separate remote transformer. Many of the devices and appliances in current useage are 5 volt DC.
Power circuits and appliances are normerly (in Australia) 240 volt AC single phase. Appliances in the 12v or 24v (or 48v) range are difficult but not impossible to locate and are generally more expensive as they currently have a limited market. For a real off grid use these more expensive appliances come into their own.
Most habitable land is serviced by reasonably reliable 240v power but power generated by fossil fuels is becoming more and more expensive. Renewable energy is readily available and costs in Australia are cheaper than the US (despite currency differences).
In Victoria, Australia a tiny house, moveable dwelling or caravan is considered by our Electrical Safety Authority as a plug in appliance and is not required to be wired by an electrical contractor. A registerable moveable dwelling is required to have a certificate of electrical safety by VicRoads as a condition of registration (together with a Liquid Petroleum gas safety certificate if applicable) however our Tiny Home is not registerable as it is 2700 wide. Notwithstanding this we propose to obtain an electrical safety Certificate.
We do intend to move away from normal practice however and establish an independant low voltage (12 or 24 v) lighting and device power circuit (12v & 5v) circuit that is linked to batteries that are charged by solar power. Being low voltage this circuit does not require all wiring to be in electrical conduit (in our steel SIP walls).
All of our 240v power circuit will be concentrated in the floor and first horizontal sip panel will be fully encased in conduit.
We propose to utilise a hybrid inverter in each tiny house to act as the interface between these two systems, directing power from PV panels to batteries first, then 240v via inverter and any excess back to the grid.