The problem with thinking too efficiently about efficiency
Hydrogen often gets criticized for having poor round-trip efficiency, but this statement is both vague and misleading. Let’s break it down to understand why. To make such a claim meaningful, two key factors need to be considered: first, what is it being used for—a flashlight, a cell phone, a car, a train, a plane, or even a remote community? Second, what kind of efficiency are we evaluating? Let’s be clear: energy is always lost when it’s converted from one form to another. This isn’t unique to hydrogen—it’s just physics.
Merriam-Webster defines efficiency as “effective operation as measured by a comparison of production with cost (as in energy, time, and money).” We would add emissions to that latter list.
If electricity can be used directly in a more efficient way, then why convert it into hydrogen? That’s a fair question. Think about vehicles, for example. If a vehicle can be directly connected to a reliable grid—like a trolley car or a subway train—then introducing an electrolyzer and fuel cell would make little sense. But what if there isn’t an easy way to connect the vehicle to the grid? That’s where portable energy storage solutions like batteries and fuel cells come into play.
For light-duty vehicles with short trips and long charging windows, batteries are often the best choice. But what if it is important to minimize downtime or to store large amounts of energy for long, high-powered trips? That’s when hydrogen starts to shine.
Some argue that hydrogen is an inefficient way to store energy because standard electrolysis has an efficiency of about 60 per cent, and using a fuel cell to convert hydrogen back into electricity is roughly 50 per cent efficient. That gives a round-trip efficiency of around 30 per cent. Sound low? Maybe. But let’s not oversimplify the comparison.
Efficiency isn’t just about energy in versus energy out, and it’s not a virtue in and of itself—it’s about balancing different costs and priorities. For example:
If you’re focused on operating costs, you might measure efficiency as cost per kilometer.
If downtime is your concern, efficiency could mean time per unit of energy transfer.
If your priority is reducing emissions, you might measure kilograms of CO2 per kilometer.
Let’s take a quick trip back to the 1990s, when automakers were focused on reducing vehicle weight to improve fuel efficiency. The goal wasn’t just better fuel efficiency for its own sake—it was about reducing emissions and operating costs. But here’s where things got tricky: when natural gas emerged as a cleaner, cheaper alternative to gasoline, manufacturers still insisted on using expensive lightweight composite storage cylinders. These cylinders doubled the cost of natural gas systems, making them less appealing to buyers and ultimately slowing adoption. Ironically, natural gas systems using less expensive but heavier steel cylinders would have still reduced both emissions and costs, even with slightly lower energy efficiency—but the focus on weight reduction distracted from the bigger picture. In this case, it could be suggested that a quest for energy efficiency led to increases in both costs and net emissions.
The lesson here? Energy efficiency is important, but it’s not the only factor that matters. Hydrogen offers a practical way to store moderate-to-large amounts of energy—especially when battery systems aren’t up to the task. It also allows us to store energy that would otherwise go to waste. After all, if electricity isn’t used when it is produced, then it is lost entirely, and its efficiency is effectively zero—so even 30 per cent is better than nothing.
Plus, exciting advancements are making hydrogen production more efficient than standard electrolysis, including biogenic methods that require little or no electricity. Hydrogen-powered solutions also provide benefits like zero emissions, fast refuelling times, extended range, and reliable performance in cold weather.
As we transition toward low-carbon energy systems, it’s likely—and desirable—that batteries and hydrogen will work side-by-side, each offering unique advantages tailored to different needs. Poorly thought-out critiques of hydrogen’s efficiency risk missing the bigger picture. While hydrogen may not be the most energy-efficient option for every application, stepping back to evaluate broader needs, values, and goals reveals its potential as an incredibly value-efficient energy solution for many use cases.
Let’s keep the conversation thoughtful and balanced—it’s about finding the right tool for the job.