Do renewables need a second grid?

On 30 August 2025, the U.S. Department of Energy’s official X (formerly Twitter) account posted a clip of the department’s leader, Secretary of Energy Chris Wright, in an appearance on the U.S. TV channel Fox Business.

In the clip, Wright claimed, “When you add wind and solar onto a grid, you don’t remove the need for coal plants, for nuclear plants, for natural gas plants that work all the time.”

Wright then claimed that solar panels and wind turbines exist on one electric grid which operates “when the wind blows or when the sun shines”, while fossil fuel and nuclear plants exist on another grid. Wright further claimed that this makes electricity more expensive as “you end up having to maintain two grids.” The clip has accumulated nearly 600,000 views on X.

Many commenters interpreted Wright as claiming that wind and solar literally exist on a second grid, separate from fossil fuel and nuclear plants. This is misleading – all these sources exist on one grid.

But it is true that wind turbines and solar panels can’t always generate electricity. Then, do we still need to keep fossil fuel and nuclear plants to provide electricity when there’s no wind or sun? And does keeping that extra generation capacity around make electricity more expensive?

As we’ll show, Wright’s claims leave out important context. Below, we’ll explain how variable renewables on the grid actually work.

Do we need two grids to support renewables?

Solar panels and wind turbines do not literally exist on a separate grid from fossil fuel or nuclear power plants. An electric grid is a system that generates electricity, transmits it, and delivers it to the people who use it, like homes and workplaces. While different groups may operate different parts of it, an electric grid is ultimately a single system.

If there really were “two grids”, they’d need to be two separate systems operating independently of each other. Your house would need to continually switch between the two, or have two separate sets of outlets.

However, Wright’s claims do raise a different question. If we are transitioning from a grid dependent on fossil fuels and nuclear to a grid dependent on renewables, are we replacing the old generators, or are we building solar and wind in addition to them? In other words, are we building a “second grid” by doubling the amount of generation on the grid?

The answer may be closer to the latter. A fully renewables-based grid is certainly possible, but when experts have modeled what it could look like, they’ve estimated that it will need significantly more capacity than a grid dependent on fossil fuels^[1-3]. In their models, because solar and wind are intermittent, not all this capacity will be used at once.

How has this played out in reality? For one small example, let’s look at Denmark, which got over 70% of its electricity from solar and wind in 2024. The Danish grid’s total capacity nearly doubled from about 8.8 gigawatts in 2000 to 15.7 gigawatts in 2024, even as actual electricity consumption stayed about the same over that time period. 

Nearly all the new capacity came by building new solar panels and wind turbines, raising their total capacity from 2.4 gigawatts to 11.5 gigawatts over that time period. Again, Denmark simply added the new solar and wind to its existing grid – it didn’t literally build an entirely separate grid for them.

It’s easy enough to get caught up in the numbers, but what does this actually mean for the people who use that electricity? Wright’s comments might suggest that the extra capacity translates into higher prices you pay for electricity. As we’ll show below, the evidence doesn’t really support this idea.

Renewables aren’t necessarily more expensive

It’s often claimed that renewables are expensive to maintain or that renewables increase the price that people pay for electricity – Wright is not the first to make such a claim. Like those claims, Wright’s claim that adding renewables to the grid makes electricity “always more expensive” is at odds with available data.

We’ve explained this in another article, and detailed some of the other factors that do affect electricity costs – you can read more there.

Let’s look at Denmark again. A 2019 study found that Denmark’s buildout of renewables actually decreased the cost of generation^[4]. 

The cost of generation isn’t equal to what households pay for electricity, but the prices that Danish households actually paid for electricity stayed flat between 2008 and 2019, even as wind and solar rose from 18 percent to 58 percent of Danish electricity generation. 

Danish electricity prices have risen since 2019, but – as is the case across much of Europe – this is largely due to a natural gas price shock from the Russian invasion of Ukraine in 2022.

In general, more solar and wind doesn’t necessarily translate into higher bills. Let’s look at this across U.S. states. If solar and wind did make the grid more expensive, we might expect states with more solar and wind to have more expensive electricity – but we don’t really see any such correlation.

In fact, some of the states with the cheapest electricity are states in the Great Plains or Rocky Mountains that get much – in some cases, most – of their electricity from wind turbines (Figure 1). 

It’s a widely acknowledged reality that solar and wind are now cheaper than fossil fuels across much of the world. We can examine each source’s cost at a glance by looking at its ‘levelized cost of energy’, or LCOE. This number includes both the costs of building a generator and the costs of operating and maintaining it – such as buying fuel and paying the wages of power plant workers.

If solar and wind really are “always more expensive” to maintain than fixed power sources, we might expect that solar and wind have higher LCOEs than fossil fuels, but this isn’t the case. Around the world, solar and wind have lower LCOEs than both gas and coal, and they’ve also dropped in price more quickly (Figure 2).

Wright talks about economics, but people who support renewables have other reasons. Fossil fuels still produce most of the world’s electricity today, but decades of scientific evidence have shown that burning fossil fuels produces greenhouse gases that raise global temperatures^[5]. 

Burning fossil fuels for electricity also creates other air pollutants like particulate matter and ozone that kill hundreds of thousands of people each year^[6]. A 2007 study estimated that gas power plants are responsible for 2.8 air-pollution-related deaths per terawatt-hour (a terawatt-hour is, on average, roughly how much electricity the U.S. consumes in about 2 hours) and coal power plants for 24.5^[7].

The grid can use other types of backup

When Wright said that fossil fuels and nuclear power must generate electricity when renewables can’t make up demand, he alluded to a rather common practice today. Grid operators try to tap as much solar and wind as possible – because, as we’ve seen, it’s often cheaper than other sources – but when there’s less sun and wind, fossil fuels make up a larger share of the electrical mix. 

Nevertheless, there’s some crucial context missing from Wright’s claims.

For example, Wright claimed that adding solar and wind makes other power plants “turn up and turn down all the time” – but many power plants do this all the time anyway, because the amount of electricity the grid needs is ever changing (Figure 3).

Our electricity use rises and falls with the days and seasons, in tune with the rhythms of human society. We generally use more electricity during the day, when more people are awake, than we do at night, when more people are asleep. Depending on the climate, we might also use more electricity in the summer (for running air conditioners) or in winter (for heating).

In response, grid operators might only turn on as much generation as they need. Long before the current solar and wind boom, they often did this with fossil fuel ’peaker plants’ that could be switched on at short notice.

It is not inevitable that a renewables-based grid must include fossil fuels or nuclear. Wright doesn’t mention other possible solutions to this problem. For example, he doesn’t mention hydropower – hydroelectric dams are frequently used as stable sources of low-carbon electricity, and many experts assume they will continue to be used in the future.

The grid can also store energy to use later. Today, this is often done with a type of hydropower called pumped-storage hydropower. When other electric sources are running, a pumped-storage dam pumps water into the reservoir; when electricity is needed, the dam releases water to spin its generators.

According to industry numbers, the world held about 189 gigawatts of pumped-storage capacity at the end of 2024, similar to the total capacity of Brazil. In some countries, they can be a major part of the grid – in Austria, for example, pumped-storage generators account for about 30% of the country’s capacity. 

Electricity can also be stored in batteries linked to the grid. The world had installed around 110 gigawatts of battery capacity by the end of 2024, according to the pro-renewables organization REN21 – more than the total grid capacities of many small countries. Many grids are now replacing their old peaker plants with batteries.

Experts think it’s perfectly possible to power a grid with only hydro, solar, wind, and batteries. A 2019 study, for example, said that providing 100% of Europe’s electricity using those four sources is “economically competitive” and “technologically feasible”. The study suggested that such a grid would actually have a lower average LCOE than the European grid in 2015^[2].

Certainly, adding solar and wind to the grid makes the grid more complex – but, as we’ve discussed in a previous article, these are well-known problems that engineers have many ways of solving.

Why misinformation about the electric grid is spreading

Electric grids aren’t simple. Our modern civilization relies on them in order to function, but they are very complex systems with many moving parts. When something goes wrong with a grid, even highly qualified engineers may need weeks or months to identify the cause.

This complexity means that grids can be easy targets for misleading claims – certainly from those who oppose renewable energy for political reasons. Under Chris Wright’s leadership, the Department of Energy has canceled much of its prior support for renewable energy projects. Both Wright and the person who appointed him, U.S. President Donald Trump, have vocally supported fossil fuels.

In this context, we note that the Department of Energy’s X account has recently made multiple posts attacking wind and solar and promoting fossil fuels (here are two examples). We also note that the U.S. Department of Energy recently published a report on climate change, which contains numerous misleading statements and misrepresents the work of many climate scientists.

References

1. Colbertaldo et al. (2019) Impact of hydrogen energy storage on California electric power system: Towards 100% renewable electricity. International Journal of Hydrogen Energy.
2. Child et al. (2019) Flexible electricity generation, grid exchange and storage for the transition to a 100% renewable energy system in Europe. Renewable Energy.
3. Gils et al. (2017) Integrated modelling of variable renewable energy-based power supply in Europe. Energy.
4. Sorknæs et al. (2019) Quantifying the influence of wind power and photovoltaic on future electricity market prices. Energy Conversion and Management.
5. IPCC (2021) Sixth Assessment Report.
6. Lelieveld et al. (2023) Air pollution deaths attributable to fossil fuels: observational and modelling study. The British Medical Journal.
7. Markandya and Wilkinson (2007) Electricity generation and health. The Lancet.