The single biggest challenge to being able to offer stable and reliable mobile phone services in Africa is power. Or more precisely, the lack of reliable power at telecoms tower sites. Hundreds of thousands of towers across the continent are located in areas without access to reliable electricity grids – or indeed, any electricity grid at all – and they typically have to be powered by diesel generators 24/7. And as the networks expand into ever more rural areas, the problem is getting worse as Africa is the only region in the world where the population is growing faster than the rate of electrification.