Despite sunny Australia now leading the world in rooftop solar PV (after a late start), with renewable energy capacity per capita growing ten times faster than the world average in 2019, it's still using less than 5% of potential rooftop capacity in 2019, and could provide more energy than national consumption from all usable roofs. Renewables like solar can also be combined synergistically with other land uses like agriculture and total Australian renewable energy capacity could even be taken up to 700GW (20 times current peak demand) to generate about 7 times total annual electricity demand if excess power was stored or exported to Asia as is planned for solar power in the Northern Territory.
The global potential from wind energy is equally massive, with just land-based wind power in tiny Europe able to provide the entire world's energy and off-shore wind & wave power resources being even greater, for example off-shore wind could supply four times the electricity demand of US east-coast states, and seven times the UK's electricity needs.
But as continued cost reductions and pressure to reduce emissions drive an increasing uptake of renewable energy, these huge impending changes in power generation bring further large challenges and opportunities for how we manage electricity grids. Replacing absurdly expensive & unreliable long transmission lines to remote areas - which can cost over $25,000 per customer, per year - with stand-alone power supplies are a long-overdue no-brainer, but managing rapidly-growing distributed generation like rooftop-solar along with batteries situated across communities and in electric vehicles (which has huge potential with "V2G") within established, large-scale electricity networks is more complex. However, with solar PV + batteries in most homes we could have just low-power micro-grids connecting them (at least at a local level), which would only need capacity for net average demand to keep batteries sufficiently charged - less than 1 kW for a typical home (compared to peak loads of several kW) or maybe around 50W with a decent home PV-battery system, or 1A at a fairly safe 50V DC. Whilst this is more than a standard phone line can carry, the resistive loss on a 50-metre coax cable (or equivalent size) could be kept to about 10%, which may not be very good by typical electricity supply standards, but would be only about 1% of total consumption and perhaps justified by the savings in system supply costs.
In Australia this could potentially have been done with the NBN's copper + HFC (Optus coax) phone network to the kerb / "node" (copper installed cost-effectively in parallel with fibre) + node-to-home electrical wiring (perhaps using existing electricity power wires from kerb to home), but now hopefully can be done instead with its replacement - the NBN's "fibre to the kerb" model, which may need parallel power wires anyway and shouldn't cost much to upgrade the electrical capacity beyond that needed for the NBN only (since most of the cost is for installing the new NBN cables rather than the cable itself, although see here for a community-based approach to low-cost cable installation).
The NBN's electricity network could then compete with the existing electricity distribution networks (who don't want to let solar + batteries undermine their fixed access charges & asset values, as this article shows) and improve the economics of the NBN roll-out. And updating this at June 2017 - it looks like Telstra are well-positioned to pursue this!
This competition would substantially reduce the need for regulatory management of electricity network rules, which governments will always struggle to get "right" (this point is perhaps reinforced by the recent disappointing Parliamentary report on the issues, which my attached rant responds to!).
Smart PV grids might be "controlled" by a distributed intelligence system for power management within the local micro grid, using local price signals facilitated by block-chain technology (at every premise / network node), rather than having an all-knowing, super-powerful centralized control system. This could be important as neighbouring micro-grids start to impinge on each other and optimising across the artificial boundaries is needed. A distributed intelligence/local pricing approach should be more scalable. (Incidentally, similar approaches may be needed to optimise dynamic traffic management with automated vehicles in the transport sector, and the NBN's cables could potentially be installed (cost-effectively) in tubes buried under roads that could be used to safely guide such driverless vehicles.)
Although the cost of PV + batteries is falling rapidly, the economics might not quite stack up for a few years yet for some existing homes, from only the home-owners' perspective. However, for new housing developments there could be extra value on offer to society from avoiding the costs of installing higher capacity local grids that would only be needed for a few years (until PV & battery systems are even cheaper) and also from the investment in "systems knowledge" that can be gained from prototype systems, which will enable more efficient systems to be delivered rapidly when lower costs justify mass roll-out in only a few years from now.
Having said that, the costs of solar PV + batteries have now fallen so low since I first wrote this (& continue to fall) that even supporters of the technology are now saying that they no longer need subsidies (like emissions trading), just updated market rules that will recognise and value the superior rapid response and system support provided, which Tesla's flexible battery system in South Australia demonstrated so effectively in response to a coal power station failure only a couple of weeks after the battery's commissioning.
See these links about solar "smart grids":
and these for the economic problems facing the NBN mark-2, which will also soon face tough competition from 5G mobile (it needs a "plan C"!):
The reported "blowout in remediation costs for Telstra's copper nodes, totalling $641 million" would be a bargain price if it could be used for a competing electricity network!
& check out these Australian companies seeking to transform how we invest in & sell electricity:
Sydney Renewable Power Company, offering community/stakeholder investment in solar power projects, starting in Sydney
DC Power Co. (Disclosure: I bought $500 of their shares)