The volatility of wind off the Atlantic coast will challenge New York’s ability to keep the lights on according to a recent analysis from the New York State Reliability Corporation (NYSRC). This study reveals the critical weakness in the state’s energy policy — the need for long-term reliable backup power — and underscores the tremendous cost of heavy reliance on expensive and unreliable offshore wind.

In its bid to electrify buildings and transportation while eliminating natural gas-fired power plants, New York plans to develop as much as 18,000 megawatts of wind power by 2050, enough, in theory, to more than meet the current peak demand of New York City.

The analysis of 21 years of wind data showed that wind lulls, defined as wind power output that falls to just 5 to 20 percent of potential output, are dangerously common. Lulls lasting 24 hours or more occur about 30 times per year, with lulls of 48 hours or more happening about seven times annually and lulls of 72 hours or more happening about three times per year. Over the entire two decades of data analyzed, wind lulls of up to 86 hours (about three and a half days) with an average of only five percent of potential output were observed at all seven study sites. Most of these lulls occurred during summer.

Making matters worse, these wind lulls are interregional. New York will not be able to turn to nearby states for extra power because they will be suffering the same decline in offshore power production as they, too, become more reliant on wind.

The risk will grow in the future as downstate New York becomes more reliant on offshore wind. The Climate Leadership and Community Protection Act requires the installation of 9,000 MW of offshore wind power potential by 2035, but the Climate Action Council’s Scoping Plan calls for 18,000 megawatts by 2050. That’s roughly equal to 18 or more nuclear or natural gas power plants. A lull that drops wind power output to between 5 and 20 percent of potential is equal to 14 to 17 of those power plants going offline at once.

While electric system operators engage in ongoing planning for handling unexpected power losses on the grid, they assume a worst-case scenario might be disruptions in just a few electricity production or transmission assets at once. Nobody has yet planned how to ensure an uninterrupted power supply when the equivalent of more than a dozen power plants in the same region go offline simultaneously.

This means that to avoid massive loss of electrical load on a nearly weekly basis in the summer, New York will have to find a reliable backup power source.

The state’s existing hydro and nuclear sources cannot be that backup because their production is already fully committed for regular power needs. The state’s future solar and onshore wind resources also cannot be the backup, both because their generation will be committed for regular power needs and because they are not reliable enough to be dispatchable as needed. Modular nuclear power could potentially be that power source in the future, but rather than being a backup for offshore wind, it would eliminate the need for it.

That leaves some kind of energy storage system as the backup power source. The only two plausible alternatives on the horizon are battery power and hydrogen. The cost for full battery backup to cover an 85-hour wind lull could run into the hundreds of billions of dollars. As batteries last only about ten years, full battery backup could require annual spending on replacements of potentially tens of billions of dollars. And while a lull in offshore wind production could put the state in need of hundreds of thousands, or even more than a million, megawatt-hours of backup power, as of 2019 the United States as a whole had less than 2,000 megawatt hours of battery backup, a pittance of New York’s potential requirements.

The other alternative is hydrogen, a clean-burning gas that can be made from seawater and clean energy, so that it has no greenhouse gas emissions. Currently, it is still far too expensive to be a plausible alternative, and is only produced in experimental quantities. In addition, it is very challenging to transport because it corrodes metals, and as the smallest molecule it leaks easily from pipes. That all may change for the better over the next several decades, but it is too uncertain at this time to plan a system that relies on it.

So, the backup the state will need is not yet available and may become available only at a very high price.

Adding to the uncertainty, it’s also difficult to know just how much backup power will be needed, because it’s unclear how reliant New York will let itself become on offshore wind. That 18,000 megawatts of turbines could produce as much as 432,000 megawatt hours of energy in one day, but with a wind lull they would only generate between 21,000 and 86,000 megawatt hours of electricity.

If the state chooses to rely on a lower amount of output as its “normal” for offshore wind production, then it doesn’t need to build as much storage backup to cover offshore wind lulls. But it will need more of other sources of power to rely on. Given the state’s policy commitments and trajectory, that is likely to be onshore wind and solar. Because both of these hae even lower average output over the course of a year than offshore wind, that could, ironically, increase the need for storage even more than a greater reliance on offshore wind would.

Unfortunately, planning for reliability cannot assume that these different power assets can substitute for each other as needed. An interregional wind lull could leave onshore wind as unproductive as offshore wind. And the occurrence of simultaneous cloudy and low wind conditions is common enough that Germany, which has preceded New York down the renewables path and experienced severe challenges to energy reliability, has coined the term “dunkelflaute” (dark lull) to refer to them. Notably, Germany’s backup power source right now is its unusually dirty coal power.

So, as a practical matter, New York will effectively need to have backup power nearly equal to its total peak demand and enough of it to power the state for several days at a time. It’s not surprising, then, that even the Climate Action Council admitted that the state will need energy storage sufficient for “days, weeks, and even longer” to maintain reliability.

Electricity consumers will, of course, be the ones who pay for this. First they will have to pay for very expensive offshore wind, one of the most expensive energy sources available, then they will have to pay for backup power due to the unreliability of that wind.

Climate activists may not be concerned about costs, but most of the public is. Increasingly, so are state leaders. When the choice comes down to either unprecedentedly high electricity costs or enduring regular blackouts, New Yorkers may find getting off the climate activism bandwagon their most attractive option.