You can buy sunlight with your phone, conduct an eye test on someone 100 miles away and attend a church service on your iPad. There are apps for investing in cows, for sending parcels and for mapping unrest. And soon you’ll be able to deliver blood and medicines by drone.

There’s free Facebook, mobile banking, and the promise of cashless societies and digitised land records. And from Accra in the west to Kigali in the east, a spray of “tech hubs” talk about “leapfrogging” technology and incubating start-ups.

Such are the giddy promises of Africa’s “fourth industrial revolution” – a giant step forward into the digital world which the Guardian is reporting on for the next two weeks. Some are salivating that it will amount to the renaissance of a marginalised continent, while others soberly warn of the hype.

By 2020 there will be more than 700m smartphone connections in Africa – more than twice the projected number in North America and not far from the total in Europe, according to GSMA, an association of mobile phone operators. In Nigeria alone 16 smartphones are sold every minute, while mobile data traffic across Africa is set to increase 15-fold by 2020.

Smartphone connections in Africa stood at 226 million by the end of 2015 and are forecast to increase to 720 million by the end of 2020.

Twenty per cent of the continent already have access to a mobile broadband connection, a figure predicted to triple in the next five years. The mobile industry will account for 8% of GDP by 2020 – double what it will be in the rest of the world. And internet penetration is rising faster than anywhere else as costs of data and devices fall.

Sparks of inspiration

Millions in Africa have simply bypassed traditional infrastructure stages such as landlines and branch banking, skipping straight to cellular telephony and mobile money. The potential for further great leaps forward in business, medicine, education and public administration is high.

In other respects however, it is clear that whole segments of the population are struggling to embrace the fourth industrial revolution, with many yet to see the benefits of the first three. Only about a third of people in sub-Saharan Africa have access to grid electricity, for example.

“If you can’t have electricity you can’t drive any industrial development,” says Akinwumi Adesina, president of the African Development Bank. “Electricity drives everything, so until we fix that problem Africa faces huge challenges.” He told the Guardian that the bank is trying to leverage $150bn dollars over the next 10 years to connect another 130 million people.

“It’s the most critical issue holding back Africa’s development.”

But with a young population that is increasingly technology-aware, enthusiasm burns brightly even if the lights don’t always.

“The phone has gone beyond being a luxury item,” says Bob Collymore, chief executive of mobile operator Safaricom, east Africa’s largest company. “In the UK if you forget your phone, you can always use a card, but here it’s an essential tool for generating income, finding jobs.”

How did it happen?

Africa’s great leap forward sprang from prosaic beginnings. Half a dozen deep sea cables were draped along the continent’s eastern and western seaboards at the turn of the decade.

These high-bandwidth undersea conduits hit landing points in almost every country they passed, and those states then acted as corridors to landlocked nations behind them. Improved fixed and wireless connectivity quickly followed, with telecommunications providers in many countries upgrading from 2G technologies to 3G, and now in some urban centres to 4G.

“For almost 40 years, Africa had wanted to link to the rest of the world,” says Dr Bitange Ndemo, former permanent secretary for information and communication in Kenya. “It kept on failing until 2009, when we first got the undersea cables which lowered the cost of broadband.”

Internet penetration in Africa jumped from very low levels in 2009 to 16% of individuals in 2013 and over 20% in 2015. But the proportion of people online is still far behind the global average – 17.4% of individuals have access to mobile broadband, while fixed broadband connections remain very low. Countries will have to keep up with rising demand for bandwidth in order to drive innovation and enable the shift to digital across all sectors.

Major infrastructure expansions are under way – from upgrading and installing submarine cables and backbone networks to various experiments to get rural and peri-urban Africa online. The world’s major technology companies – including Microsoft, Google and Facebook – are deeply interested in last-mile connectivity across the continent, with its billion-plus population.

“I don’t see us having problems with capacity from the undersea cables on both sides of the continent for the next five years. It’s capacity inland that is of concern to me,” says Mteto Nyati, chief executive of MTN South Africa, the country’s second largest telecoms company by market share.

“If we’re talking high-speed, we need to be going LTE [long-term evolution] and in the future 5G – the digital migration to free up other frequencies needs to happen in Africa, otherwise we’ll have bottlenecks.

“We need partnerships between governments and mobile operators to help them with this migration if they can let the resources become available.”

Just as mobile telephony has had a massive impact on economies in Africa, the hope is that the internet will also have a transformative impact.

In 2013, McKinsey estimated that the internet’s contribution to Africa’s GDP was 1.1%, just over half the levels seen in other emerging markets. But the same report – taking into account the magnified impact of mobile in emerging economies – projects that the internet could potentially contribute 10% of GDP – $300bn – to the African economy by 2025.

Digitisation efforts include bringing businesses of all sizes online, bringing government and its services online, public-private partnerships, and the development of enterprises that are pure internet players.

“Those who are already online – whether in healthcare or agriculture, in services, in e-commerce – they have a faster uptake around technology adoption,” says Amrote Abdella, regional director of Microsoft4 Afrika, an initiative founded to help bring SMEs online.

“What is still missing and this is what we are trying to understand, your average mom and pop shop that is completely invisible and is working and functioning in the informal market,” she adds. “How do we bring them to get online and how do we formally create the channel that allows them to access finance, to bring their business online, to access new markets?”

International investment

By 2012, investors, some of them overseas, were starting to take an interest in this economic potential. People like Mbwana Alliy, a Tanzanian who was working in Silicon Valley. He raised a small fund in 2012 to look at promising tech companies. And the spread of investment says something about where the promise lies.

Of 22 companies that Alliy’s Savannah Fund invested in, 10 are in Kenya, four in Nigeria, three in South Africa, two in Ghana, two in Uganda and one in Zimbabwe.

“Nigeria wins on market size,” he says over a beer in a restaurant in the Rwandan capital Kigali. “It’s massive, it’s a great place to work with consumer products – Nigerians are culturally wired to consumer more than others.

“South Africa has the best infrastructure and education, while in Kenya mobile money is a big deal, and it has good policies for tech,” he adds.

Some investors pinpoint financial services as an attractive, albeit risky, area, following on from the way that technology like M-Pesa mobile money has opened up banking to millions of people who could never have hoped to own bank accounts in the past. According to GSMA, there are 223m registered mobile money accounts in sub-Saharan Africa. More than $5bn moved through mobile accounts in December 2015 alone.

E-commerce is another story showing promise, particularly in large markets such as Nigeria, where Jumia Group has just been valued at over $1bn, making it Africa’s first tech “unicorn”. The group, which encompasses multiple digital ventures from shopping to classifieds to taxi apps, operates not only in the continent’s most populous market but in 22 others as well.

“The entrepreneurs behind Africa’s digital economy are trying to build for the future – and it’s hard, brutally hard,” says Jason Njoku, chief executive of Nigeria’s iROKOtv, which has raised over $35m from international venture capitalists. “Most are chasing international investment, because the vast majority of African investors largely ignore tech and prefer to fund agriculture, oil, gas and other more traditional sectors.

“So what now? We need to get our own, homegrown investors on board, to understand the opportunities that are right under our noses.”

“It’s a tricky market – there is political risk, it’s a very young sector,” adds Manuel Koser, founding partner of Silvertree Capital, which invests in tech companies in emerging markets. “A lot of investors are still unsure if this is a good asset class.”

Rwanda looks ahead

If Kenya, South Africa and Nigeria are the big three in the sub-Saharan tech world, then Rwanda is styling itself as something of a poster child for digital: small, nimble, open for business.

“Rwanda, where ICT is the future,” an airport billboard declared recently. A cynic, regarding an agrarian economy where some people still don’t have running water, might say, “Yes, indeed, because it certainly isn’t the present”.

But that would be unkind. As technology minister Jean Philbert Nsengimana explains, Rwanda has spent 15 years digitising its economy, its healthcare and education. And now it has eyes on becoming Africa’s first cashless society – at least where the public sector is concerned.

“There is a limit to how much a government can engineer a cashless society,” he says, “but government itself will be cashless by the end of next year.”

Innovation is often more bottom-up than top-down, though.

“What’s interesting now among African startups is that they’re less about something really innovative in a specific app itself, but rather they are thinking about innovative ways to solve real problems in the market,” says Ory Okolloh, a well-known technology commentator.

Or they are trying to solve a social problem. For example, Africa has barely one doctor per 1,000 people – low by international comparisons – and its vast geography makes home visits a poor use of time. One initiative set up by a British ophthalmologist, Andrew Bastawrous, trains local people to use diagnostics on smartphones to conduct eye tests. Clinical data is collated for experts to assess who needs treatment.

A number of startups, including one by young women called Sigestes in Senegal, are engaged in digitising land records, which may sound banal until you realise that not knowing who owns what is a recipe for tax evasion, corruption and even violence.

Then there is Cameroonian Churchill Nanje who set up a pan-African jobs search site from his bedroom, and has served more than 2 million users in 11 countries since.

Obstacles to progress

But there are buts. Many of them. Parts of Lagos still run on generators for 18 out of 24 hours. Even in tiny, top-down Rwanda, just 25% of households are connected to the grid. Sneha Shah, Thomson Reuters managing director for Africa, says: “It’s not just that they don’t have the ability to generate power; they don’t have the ability to distribute the power.”

And infrastructure problems don’t stop there. Poor roads and the absence of formal address systems make logistics arduous and costly for online retailers. Connectivity in the hinterland can be non-existent, and connecting the very last mile out in the wilds does not always make economic sense.

“There are access issues in rural parts,” says Ndemo. “These are places where the cost of deployment may not be recovered in a short space of time and so those places get marginalised. In Kenya, we had introduced an infrastructure-sharing policy in such places – there would be one mast and other networks could use it.”

Then there is the affordability issue. When the cost of the average smartphone fell below $100 last year, it was hailed as a breakthrough moment. But that doesn’t take into account the cost of data.

“Young people are very conscious of how apps on their phones are using data,” says Mnikelo Qubu, head of digital at Kenya’s Well Told Story, which produces a popular multi-platform storytelling project targeted at young people. “They’ll go online, download messages and then go offline again. I still consider SMS as very necessary in terms of on-the-ground reach.”

There are shortcomings both of local education and local content. Millions would be far more engaged in the internet if there was more material in their local language. That’s a tall order given the 2,500 languages and dialects spoken across the continent. And as pointed out by Josiah Mugambi, executive director of Nairobi’s iHub, training consumers in how to use technology is also essential. “In some parts of Kenya, there are people who will struggle to use a smartphone, at least at first,” he says.

“You need to address all of these levers to address internet penetration,” says Hans Kuipers, a Johannesburg-based partner at Boston Consulting Group.

Worse still, local talent is still relatively thin on the ground, at least compared with western levels. For every African whizz-kid with an app and seed funding to match, there are millions who don’t have the basic practical education to make the most of the internet revolution.

“We are sitting in a good space but we may not have the necessary skills to move beyond the space we’re in,” says MTN’s Nyati. “The good thing is that we are a young continent – these are people who are open to learning and they are familiar with technology.

“They have great ideas but are lacking the infrastructure to do software development, for example. We need to transform our education system into one that is more practical than what we have today.”

Another concern is that Africa’s tech economy will become dominated by non-local players. Already dominant western operators such as Uber, Netflix and even Amazon are poised to exploit opportunities that local competitors cannot.

Facebook has already rolled out its Free Basic offering of giveaway data packages in more than 20 countries, prompting howls from net neutrality advocates.

“Facebook is not the internet, and limiting it doesn’t give people the agency, political power or control,” says Timothy Karr from the Save the Internet campaign.

A related trend in recent years – which also demonstrates the power of the internet and mobile connectivity – has been the shutting down of networks, or certain sites, during elections or moments of crisis. Well documented during the Arab spring, shutdowns have taken place already this year in Uganda, Chad, Republic of Congo, and Ghana, often seen as a democratic role model in Africa.

“For Ghana to suggest that they will turn off the internet, in addition to other countries that have done it like Uganda, Zimbabwe, DRC, Burundi, Chad and others, that’s worrying,” says Okolloh, who co-founded Ushahidi, a crowd-sourced crisis-mapping tool that first tracked the violence that followed Kenya’s 2007 election.

“Now, when it comes to critical moments, you can’t arrest everyone in order to keep the story from getting out – so governments figure they will just shut the internet down. The telcos just shrug their shoulders. Many are powerful enough to do so, but I’ve not seen an attempt to put up a fight.”

Additional reporting by Murithi Mutiga in Nairobi and Maeve Shearlaw