Diesel generators do not charge most electric vehicles

With growing numbers of electric vehicles on the world’s roads, public places to charge electric vehicles have become an ever more common sight on curbsides and parking lots. However, some electric vehicle critics claim that these charge points are not what they seem — see this recent post on Threads for an example. Identifying a California charging station as the “largest in the world”, the post states that the station is “all powered by diesel”. The image links to a September 2023 article in Wyoming newspaper Cowboy State Daily, though the article does not repeat the claim that the charging station is “all powered by diesel”.

Indeed, claims of diesel-powered electric vehicle charge points are not new. For example, last year, a widely shared video claimed to depict a diesel-powered charger in Australia. Another, earlier Facebook post claimed that a charging station in Texas relied on diesel. These claims may leave readers with the implicit or explicit impression that electric vehicles are not “green”.

In this review, we show that such claims are misleading. The data indicates that few electric vehicles get their charge from diesel generators — most electric vehicle owners simply charge their vehicles at home, using electricity from residential grids. When they do, in all but the most coal- and oil-dependent grids, they are helping ensure that their vehicle will be responsible for lower emissions than a comparable vehicle that runs on an internal combustion engine.

The Harris Ranch charging station is not entirely diesel-powered

The charging station portrayed in the image is indeed situated on Harris Ranch, a resort in California’s Central Valley. Harris Ranch does host 98 charge points operated by Tesla under its Supercharger brand, plus at least 6 non-Tesla-owned chargers.

However, other details are inaccurate. First, Harris Ranch is not “the largest charging station in the world”. As of this writing, the largest publicly accessible charging park is located at a railway station in Merklingen, Baden-Württemberg, Germany, with 259 charge points: more than twice as many as Harris Ranch. Photographs of the Merklingen charging station clearly show solar panels on-site. It is widely reported that an even larger station, containing 637 charge points as of 2019, helps recharge a fleet of electric taxis in Shenzhen, China.

Second, the Harris Ranch station is not “all powered by diesel”. Both Tesla itself and independent research say that Tesla Superchargers are connected to the electric grid by default. Furthermore, since mid-2023, solar panels have been clearly visible at Harris Ranch on Google Maps, indicating they provide some of the chargers’ energy.

The claim that the station is “all powered by diesel” appears to descend from a 2022 Slate article, in which journalist Edward Niedermeyer recounted finding a diesel generator during a May 2015 visit to Harris Ranch. However, Niedermeyer did not say that the generator had powered the entire charging station. Instead, he reported that the generator had provided additional electricity during a temporary period of high demand.

A Harris Ranch spokesperson corroborated this story to SFGATE in 2022, stating: “The temporary emergency generator was operated by Tesla to only provide power for the mobile Supercharger unit, during the retrofit of the permanent site in 2015.” (Science Feedback reached out to Harris Ranch for confirmation but has not received a response.)

The vast majority of EVs charge on the grid, not from diesel generators

Today, people often use portable diesel generators as backups in case of a power outage or in remote locations where the main electrical grid is inaccessible. The aforementioned claims about Harris Ranch and about other charging stations may mislead readers into believing that diesel generators are also a common means of charging electric vehicles. This is false. Data suggests that most electrical vehicle owners charge their cars at home, almost always drawing electricity from the same main grid that powers kitchens and charges mobile phones^[1].

A 2024 International Energy Agency (IEA) report collected country-level numbers on how many electric vehicle owners could access a home charger. (“Though access to charging is different to actual use, it is a useful proxy for the levels of home charging among EV owners across countries,” the report notes.) 55% of EV owners had access to a home charger in India, 71% in Mexico, 80% in Canada, 82% in Norway, 83% in the US, and 93% in the UK. This is despite the fact that these countries have vastly different rates of electric vehicle adoption. For example, less than 2% of new cars sold in Mexico in 2023 were electric, compared to more than 90% of new vehicles in Norway that year^[1].

In comparison, as we see in Figure 1, public chargers make up a comparatively small portion of charge points. Most public chargers are connected to the main grid, like their private counterparts. Some public chargers — such as the Tesla chargers at Harris Ranch, or the charging station in Merklingen — come with solar panels to provide additional electricity, but solar panels are not diesel generators^[2].

Where EVs have been charged from a diesel generator, they have been charged as a backup solution or in areas where connecting to the grid is impractical — the same reasons that one might use a portable diesel generator in the first place. Some engineers have experimented with standalone EV-charging microgrids, isolated from the main grid, which primarily rely on wind or solar power and use a diesel generator as a backstop^[3,4]. The Australian charge point at the center of some diesel-charged-electric-vehicle claims actually used a diesel generator as a backup for a predominantly solar-powered setup in a remote part of the Australian Outback. One company sells a diesel generator and charging station for over $200,000, explicitly describing it as “a temporary fast-charging station […] for temporary sites and remote areas.” 

These are niche use cases, and the IEA’s data clearly indicates that charging EVs with a diesel generator in public is not the norm.

Electric vehicles are usually responsible for lower emissions than combustion vehicles

The claim that charge points run on diesel generators belongs to a larger category of claims that scrutinize electric vehicles’ energy sources. These claims can mislead readers into believing that electric vehicles have a larger greenhouse gas footprint than their petrol-powered counterparts. 

In reality, the opposite is true. Electric vehicles do have a greenhouse gas footprint, much of it from manufacturing their batteries. But (as we explain in this article in French) if we compare the emissions from an electric vehicle to those of an equivalent combustion vehicle over the entirety of each vehicle’s lifetime, we find that the electric vehicle is responsible for fewer emissions in most circumstances.

Logically, the lower the carbon intensity of a country’s electric grid, the smaller the footprint of a vehicle that charges on it. However, even electric vehicles charging on fossil-fuel-dependent electric grids are still generally responsible for lower emissions than their petrol- or diesel-powered equivalents. According to figures published by the Intergovernmental Panel on Climate Change (IPCC), an electric vehicle’s emissions per passenger per distance traveled compare to those of an equivalent combustion vehicle only in a scenario where an the electric vehicle is powered entirely by coal-fired electricity (whose greenhouse gas emissions are high even by the standards of fossil fuels)^[5].

Consequently, an electric vehicle usually has a significant emissions advantage over an equivalent combustion vehicle. One study estimated how an electric vehicle’s greenhouse gas emissions compared to those of a newly manufactured combustion vehicle, across both vehicles’ entire life cycles, in 59 regions around the world, using data from 2015. An electric vehicle reduced the life-cycle greenhouse gas emissions on average in 53 of those regions, together accounting for 95% of the world’s transport demand^[6].

Other studies have come to the same conclusion: that electric vehicles have an advantage on all but the most fossil-fuel-dependent electricity grids. For example, a second study compared the CO2 emissions of electric vehicles with those of equivalent combustion vehicles across 32 European countries; in every studied country save for Poland, Serbia, and North Macedonia, the electric vehicle was responsible for fewer total CO2 emissions over its lifetime^[7].  A third study compared an electric vehicle to a gasoline-powered hybrid (which is responsible for lower emissions than a solely gasoline-powered vehicle) across 35 countries; in 26 of the 35 countries, the electric vehicle has significantly lower greenhouse gas emissions than the hybrid across their respective lifetimes^[8].

So, despite claims that imply electric vehicles are dirty due to their energy sources, they do have the advantage over combustion vehicles in most circumstances today. Moreover, if countries continue pursuing their goals of decarbonizing their electric grids, the electric vehicle’s emissions advantage will only grow^[6,8].

Conclusion

As we have shown, claims that EV charging stations are diesel-powered are inaccurate and misleading. Most electric vehicles get their power from the main grid. Diesel-generator-powered charge points do exist, but they are not the norm, and they are only used in very rare circumstances when accessing the main grid is difficult. In most contexts, claiming that this makes electric vehicles less “green” is also misleading. Over the course of its lifetime, an electric vehicle usually has an emissions advantage over an equivalent combustion vehicle, even if the electric vehicle gets most of its charge from fossil-fuel-fired electricity.

References:

1. International Energy Agency. (2024) Global EV Outlook 2024.
2. International Energy Agency Photovoltaic Systems Power Programme. (2021) PV-Powered Electric Vehicle Charging Stations: Preliminary Requirements and Feasibility Conditions.
3. Singh et al. (2020) Implementation of Solar PV-Battery and Diesel Generator Based Electric Vehicle Charging Station. IEEE Transactions on Industry Applications.
4. Mehrjerdi and Hemmati (2019). Electric vehicle charging station with multilevel charging infrastructure and hybrid solar-battery-diesel generation incorporating comfort of drivers. Journal of Energy Storage.
5. Intergovernmental Panel on Climate Change. (2022) Transport. In: Climate Change 2022: Mitigation of Climate Change.
6. Knobloch et al. (2020) Net emission reductions from electric cars and heat pumps in 59 world regions over time. Nature Sustainability.
7. Hung et al. (2021) Regionalized climate footprints of battery electric vehicles in Europe. Journal of Cleaner Production.
8. Sacchi et al. (2022) When, where and how can the electrification of passenger cars reduce greenhouse gas emissions? Renewable and Sustainable Energy Reviews.