(Bloomberg) — The next generation of telecommunications technology could be the key to ending years of stagnation in the industry. But it’s also set to create a difficult dilemma for European phone companies. Carriers shelled out $80 billion to power the world’s antennas last year, according to Nokia Oyj. The prospect of having to raise spending on electricity – energy demand could triple with the introduction of 5G equipment, according to industry body GSMA – won’t sit well with phone companies that are already struggling to pay their dividends. At the same time, firms such as BT Group Plc and Vodafone Group Plc have pledged to slash emissions, and that will require a rapid shift to renewable energy.

Just as carriers are about to roll out vast quantities of power-hungry gear, they’re also promising to save the planet. And funds are tight. Accomplishing everything at the same time could be a tall order.

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“If they have set up ambitious targets for overall power consumption and CO2 emissions, those could potentially be in conflict when they start to roll out 5G,” said Jerker Berglund, industry consultant at JB Sustainable Approach AB. “Reducing total power consumption is going to be a challenge.”

5G could unleash a 1,000-fold jump in data demand for connecting factories and cars and supercharging mobile devices, according to the GSMA. That’s an irresistible sales prospect for a telecom industry whose revenues have yet to recover from a slump that started in 2015.

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Next-generation antennas and masts can be 10 times more energy efficient than 4G’s. However, these power savings could get swamped by the surge in demand for new applications. 5G will link up billions of things that have never been connected before. To accommodate all these new connections, masts might have as many as 128 antennas, versus just four or eight on a typical 4G mast. Bouncing signals through cities may require thousands of transmitters and receivers to be bolted onto rooftops and street furniture. This looks like it will all require a lot more bandwidth, and a lot more power.

What’s more, carriers can’t afford the cost of swapping out all their equipment at once, Berglund said. The rollout will have to happen gradually, so many masts will still carry less efficient 4G, 3G and 2G antennas alongside 5G ones. This situation could last for years – some 3G kit is still in place 18 years after that technology was introduced.

Electricity already makes up about a third of carriers’ average operational costs, according to Nokia, and raising this will pressure balance sheets when the industry isn’t in a good place to cope. Vodafone has cut its dividend to conserve cash to pay for spectrum and capital investment. Bank of America Merrill Lynch analysts said Monday they expect BT to slash its dividend by as much as 40% to fund capital expenditure and price cuts.

“As we consume more, power’s going up, and the industry is trying to bring that down as much as possible,” said Henry Calvert, head of future networks at the GSMA, the mobile industry trade body. “There’s a lot of activity in the industry about making the power we use more efficient.”

But whatever fixes carriers make to lower energy bills – sharing networks, getting masts to autonomously power down at times of low data demand, introducing “beam-forming’’ so smart antennas can pinpoint devices instead of pumping out data indiscriminately – the surge in power usage creates a challenge for meeting emissions goals.

Deutsche Telekom AG, for example, pledged a 90% reduction in carbon emissions between 2017 and 2030. In total, European carriers will have to reduce carbon dioxide emissions by 6 million metric tons within 11 years to achieve their carbon targets, BloombergNEF analyst Kyle Harrison said in a research note.

One solution is for the telecom companies to shift their power supply to renewables, but this can’t be done at the flick of a switch. Clean-energy contracts are complicated and can take years to negotiate.

Carriers will be under pressure to sign new ones quickly to cope with 5G’s power demands, Harrison said. They’ll be vulnerable to striking bad deals, and price fluctuations in energy markets can turn some arrangements that initially look good into losers in the longer term.

“The switch to 5G is going to put more pressure on telecoms to purchase clean energy and reduce their emissions,” he said. “Many clean energy deals can result in losses for corporations. Telecoms will need to put extra consideration into this as their power demand goes up, especially if losses will impact their investments into 5G.”