Last week's front-page story on Eskom's stance on renewable energy stirred much debate. We have expanded the letters section to provide space for the many opinions we have received, some highly critical of my views on the matter. To clarify, I am in no way against the rapid development of technology around renewable energy so that one day we can do away with the need to burn fossil fuels.A colleague this week pegged the appearance of a tornado in Tembisa, east of Johannesburg, as evidence of climate change. I don't know about that, but I've read enough and seen enough of An Inconvenient Truth to know that there's something amiss.As for nuclear, there's merit in arguing against that option given the prohibitive upfront costs of building one reactor, let alone an entire fleet. In an economy that Barclays Africa has just forecast will shrink 0.2% this year, it seems folly to even consider it.story_article_left1A National Treasury that is in a very austere mood can't be seen to be entertaining future spending in the trillions of rands. To do so would be to fall foul of the ratings agencies, which are watching for any sign of a shift in policy or of buckling under political pressure.In this regard, continuing on the renewable path promises foreign direct investment and seems a safer route for the sovereign credit rating.There is a school of thought that says we should leave decisions about base-load replacement to another day, perhaps when the economy is once again motoring ahead and potentially on a path to that holiest of holy grails, 7% growth.But as I recall, when South Africa did near such growth levels, the lights went out.In 2007, South African growth was pencilled in at 5.5%. In January the following year, Eskom's grid failed to handle the demand on it. And of course there was the matter of a wet December.Local growth concerns began in earnest months before the US investment bank Lehman Brothers collapsed in September 2008.The extra 2100MW of renewable energy - of which only 30% is available at any given time - that has been added to the grid over the past eight years would not cover South Africa's energy shortfall if - suddenly and rather miraculously - global growth returned to pre-2007 levels. Our lights would go out again.On a costing argument, there's something wrong with the maths when it comes to our renewable push. So far, just under R200-billion has been spent on the independent power producer programme.story_article_right2The cost of building both Medupi and Kusile, which on completion will add some 9600MW to the grid, is about R240-billion.In austere times, there's something rather troubling about that comparison.Eskom's Ingula hydroelectric project, commissioned this week, was completed for R25-billion. It provides 1300MW, whenever needed.I think there's room for a rethink on renewable policy, although I'm not saying it should be scrapped.Europe, with a population of more than 740million people living on a landmass of over 10million square kilometres, has 185 nuclear power plants.Coal is still a feature of their lives, even in Germany, where it makes up about a quarter of the country's energy profile. Gas also forms part of the continent's base-load backbone.In Africa, with more than a billion inhabitants on a landmass triple the size of Europe, there's one nuclear plant with two reactors in the form of Koeberg in the Western Cape.E-mail derbyr@sundaytimes.co.za or find him on twitter @ronderby..