Like most things it depends on the market. Conventional geothermal energy (like the PAX projects in Indonesia) has been produced for over 100 years in Italy and these days operates profitably in many countries, including NZ, Indonesia, Philippines, western USA and Hawaii, Japan, Italy, Iceland.
You need to separate this proven technology from the more cutting-edge "enginered geothermal systems" (EGS) technology on which most (all?) Australian geothermal companies floated. As is now apparent, this new technology will be very difficult to implement in Australia (and in the US and Europe where other EGS development projects are underway) while the cost of energy from coal in particular is still very cheap, as you point out.
A charge on carbon dioxide emissions from coal power generation will help address this imbalance and help encourage the development of environmentally better EGS power generation over time.
Australian companies like PAX, EHR, PTR and KEN have decided to accelerate their geothermal business by moving to conventional geothermal projects overseas. PAX is trying in Indonesia but finding problems with bureaucracy and pricing, and EHR has pricing problems in Argentina. IMHO PTR and KEN should do well with their diesel-replacement strategies on islands, where geothermal power should be much cheaper than existing diesel generation, but unfortunately they're taking a very long time to get anywhere.
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