Global greenhouse gas (GHG) reduction targets to prevent widespread catastrophic climate change require a global switch to low and zero emission electricity and heat generation technologies within a very limited timeframe. GHG mitigation technologies have different profiles for offering base load electricity and different expected levelized unit costs. A literature review and elite interviews are conducted to assess the economic competitiveness and technical viability of various technologies, both established and emerging, with especial attention to views that dissent from the prevailing orthodoxy. Advanced CANDU reactors embody important advances that make them potentially competitive with natural gas fired electricity generation. Wind is economically and technically feasible up to 20% of a typical national jurisdiction’s energy mixture. Solar and other renewables suffer from considerable economic and technical barriers that preclude significant market penetration.