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Although these scenarios sound very positive, and the supply and balancing costs look manageable, can the expansion of renewables for all energy, not just electricity, really be achieved on the timescale they suggest? As noted in chapter 1, some critics think not. For example, leading energy analyst Vaclav Smil concluded that ‘replacing the current global energy system relying overwhelmingly on fossil fuels by biofuels and by electricity generated intermittently from renewable sources will be necessarily a prolonged, multidecadal process’ (Smil 2016).

New technology development, and more so system change, takes time, but the view that it is inevitably a slow process has been challenged (Lovins et al. 2018; Sovacool 2016). It has been argued that the transition to 100% renewable electricity could occur much more rapidly than suggested by historical energy transitions (Diesendorf and Elliston 2018), with concerns about climate change helping to speed the process.

The recent pace of development and take-up of PV and batteries, as well as electric vehicles, certainly suggests that change can happen quickly. Although there has been no shortage of speculation over the likely impact of ‘destructive innovation’ of this sort on energy industry incumbents, there have been proposals for the very rapid expansion of renewables in response to what some have portrayed as a climate emergency, for example to around 80% of UK electricity by 2030 (Greenpeace 2019). The global Extinction Rebellion campaign even called for ‘zero carbon’ by 2025 in an attempt to shift the definition of what is politically possible, so as to make it more in line with what is deemed scientifically necessary for ecosystem survival (ER 2019).

However, although the public mood may be changing, especially amongst the young, and renewable growth continues, it is wise to be a little cautious about what can be done in practice and how quickly it can be done: it may take time, and the political context sometimes does not support too much optimism. Support levels for renewables have been cut in many countries so, some say, the initial subsidy-based boom may falter.

Certainly, although investment levels have risen over the years, they have recently fallen off (BNEF 2019; IEA 2019b). Part of that may be due to the fact that new projects are cheaper, so less capital is needed to get the same energy output and economic return. Nevertheless, with less investment, the overall rate of capacity growth has slowed, with annual additions falling. Even so, cumulative capacity and output are still rising, and that looks set to continue in the years ahead (Wartsila 2019). Moreover, given the political will, it could be accelerated. For example, a study by the German BDI industrial forum suggested that getting renewables to near 90% of power by 2050 in Germany as part of an 80% greenhouse gas emissions-cut scenario could be technically feasible with the necessary support. Going further to a 95% emissions cut, with renewables supplying 100% of electricity, and also meeting other energy demand, was conceivable but was likely to be very expensive. The BDI said that would be challenging socially and also economically if Germany tried to do it alone without other countries adopting similar approaches (BDI 2018).

I will be looking at the overall cost of transitions like this in chapter 8 but, for Germany, the BDI put the overall net additional investment needed, set against the likely savings, at around €470 billion and €960 billion respectively (for the 80% and 95% emissions cuts) by 2050, or roughly €15 billion and €30 billion per year, around 0.4–0.8% of Germany’s gross domestic product (GDP).

That is all a little speculative and some way off, whereas for the moment the reality is that, although funding programmes are continuing, investment-level growth in Germany and elsewhere is falling. Some critics argue that the recent fall in investment is due to the realization that renewables are expensive and that supporting rapid expansion with subsidies passes on unsustainable costs to consumers or taxpayers. That argument has been used in Germany, where guaranteed-price feed-in tariffs, which were very successful at building up renewable capacity, have been cut back and replaced by competitive project auctions in order, ostensibly at least, to cut the subsidy cost to consumers. The result has been a slowdown in renewable capacity build, which some see as the real aim, given the apparent hostility of some of the energy utilities to rapid renewables expansion that was undermining their markets. The economics of renewables can certainly be contentious: for example, they are allegedly getting cheaper, so why have consumer costs risen (see Box 2.2)?