Executive Summary

• Joost Wendling, Business Developer at Zepp Solutions compares hydrogen fuel cell generators to battery packs and explores why this debate is relevant for operators where grid connection delays, expansion plans or backup power strategies are putting pressure on conventional energy infrastructure.
• A hydrogen fuel cell generator converts hydrogen into electricity on-site, which makes it more suitable for long-duration applications, in comparison to battery packs, which are typically used for short-duration backup strategies.
• Battery packs make a better option when the energy demand is relatively low, the load profile is intermittent, and charging can be organised easily on site or nearby; hydrogen fuel cell generators become more attractive when the problem is a sustained energy supply.

 

Battery packs and hydrogen fuel cell generators are often presented as competing alternatives for zero-emission temporary, off-grid and grid-constrained power. That comparison is increasingly relevant for data centre operators and developers, especially where grid connection delays, expansion plans or backup power strategies are putting pressure on conventional energy infrastructure. But batteries and hydrogen fuel cell generators do fundamentally different things. A battery stores electricity. A hydrogen fuel cell generator produces electricity on-site. That difference may sound technical, but in practice it impacts uptime, logistics, transport costs, operational risk and, perhaps most importantly, total cost of ownership.

For some projects, a battery pack is clearly the better solution. For others, especially when energy demand is high and continuous, a hydrogen fuel cell generator has important advantages. So the real question is not which technology is better in general, it is: which one fits your application best?

Storage versus generation

A battery container is an energy storage asset. It has to be charged before use and recharged after use. If there is no sufficiently strong grid connection on site, that charging needs to happen somewhere else, or the battery has to be swapped for a full one.

A hydrogen fuel cell generator works differently. It converts hydrogen into electricity on-site. As long as fuel is supplied, it keeps generating power. That makes it comparable to current diesel-powered solutions, and fundamentally more suitable for long-duration applications or projects where energy demand continues day after day.

For data centres, this distinction is especially important. Batteries are already widely used for short-duration backup and bridging power, where they can respond instantly and support critical loads during a transition to another power source. But when the challenge is sustained operation over many hours or days, the question changes. At that point, the issue is no longer only how quickly power can be delivered, but how much energy can realistically be stored, replenished and managed on site. This is where hydrogen fuel cell generators can become relevant as part of a broader resilience or grid-constrained power strategy.

A practical example: 500 kW of continuous power

Let’s take a realistic grid-constrained, zero-emission data centre example. Assume a new or expanding facility has secured most of its grid capacity, but still faces a shortfall of 500 kW during the first few years of operation. If that 500 kW supplementary power requirement runs for 24 hours per day, 7 days per week, it equals 12,000 kWh per day, or 84,000 kWh per week. Similar power requirements could also arise from zero-emission onsite backup power needs or from temporary electricity demand during the construction phase of the data centre.

What that means for a hydrogen solution

With hydrogen, the starting point is fuel consumption. Hydrogen contains about 33.3 kWh/kg. Modern PEM fuel cell generators convert hydrogen into electricity at high efficiency. Using a system efficiency of 55% as a realistic reference point, 1 kg of hydrogen delivers around 18.3 kWh of electricity.

For 12,000 kWh or 12 MWh per day, that means a daily hydrogen consumption of around 655 kg. Over a full 7-day week, that comes to around 4.6 tonnes of hydrogen.

Now, to translate that into storage and logistics: a 40 ft hydrogen storage container (MEGC) can hold a little over one tonne of hydrogen, with exact capacity depending on pressure, configuration and supplier. In this example, the site would therefore need a little under two-thirds of a 40 ft MEGC per day, or around 4 to 5 MEGC-equivalent loads per week.

That may sound like a significant fuel requirement, and it is. But the operational point is that the generator equipment itself remains in place. The on-site energy system stays the same. The logistics revolve around replenishing fuel rather than repeatedly moving large energy storage assets on and off site.

In many cases, the delivery of hydrogen and the connection of a tube trailer, MEGC or other storage solution to the generator set is arranged by the gas distributor as part of an established supply workflow. In other words, the operator does not need to build or manage a completely new logistics chain from scratch. With a long-term offtake agreement, it may also be possible to agree on supply volumes and pricing in advance. That gives operators more predictability on fuel costs and makes the total cost of ownership easier to estimate and manage over time.

What that means for a battery solution

Now look at the same site from a battery perspective. The site needs 12,000 kWh, or 12 MWh per day. So for one day of autonomy, you need at least that much usable battery capacity. In practice, that usually means more, because operators need some margin for peaks, temperature effects, degradation, depth-of-discharge limits or operational flexibility.

Assuming a large 40 ft battery container provides around 4 MWh of usable capacity, even one day of operation would require around three 40 ft battery containers. Those containers

would then need to be recharged every day, or swapped for charged units, if the site is to keep running continuously.

If the goal is to cover a full 7-day week without intermediate recharging, the battery requirement becomes at least 84 MWh usable, before adding operational margin. On the same assumption of 4 MWh usable per 40 ft container, that means around 21 40 ft battery containers. With a practical operational margin, the real-world requirement could easily move into the 22-25 container range.

That is a very large mobile battery setup, and the logistical challenges that come with it quickly become significant. This is why the key battery question is not “can it deliver 500 kW?”. If you select the right battery system, it definitely can. The real question is: how often do you need to recharge or swap it, and where does that energy come from if the grid connection is already constrained?

So when does each technology make sense?

In general, battery packs make the most sense when the energy demand is relatively low, the load profile is intermittent, and charging can be organised easily on site or nearby. In those cases, batteries are quiet, efficient and operationally simple. If the battery mainly serves as a buffer for peaks rather than the main source of power, it is often the most logical solution.

Hydrogen fuel cell generators become more attractive when the problem is not storage, but a sustained energy supply. That is typically the case when daily energy demand is high, operations run for long hours or multiple shifts, grid access is limited, and minimising transport movements matters. In those situations, the ability to keep the generator in place and only replenish the fuel can make a major difference in logistics and total cost of ownership.

There is no universal winner in the comparison between hydrogen fuel cell generators and battery packs. There is only a good or bad fit with the application. That is why the starting point should always be the duty cycle: how much energy is needed, for how long, under what site conditions, and with what infrastructure available. Once those questions are answered, the technology choice usually becomes much clearer.