Why humanoid robots run for only a few hours on a battery

Humanoid robots usually run for about two to four hours per charge because a walking, balancing machine draws power constantly, and a battery small and light enough to carry on its back holds only a limited amount of energy. Manufacturers are not waiting for better cells. They are designing around the limit with quick-swap packs, robots that change their own batteries and very fast charging docks.

What manufacturers actually state

Published runtimes are short across the market, and many companies give no figure at all.

• Unitree G1: Unitree lists a 9,000 mAh quick-release battery at 54 V and a runtime of about 2 hours, on a robot weighing about 35 kg with the battery fitted.
• Unitree H1 and H1-2: Unitree states a 15 Ah battery of 0.864 kWh with a maximum voltage of 67.2 V, and says the battery can be replaced quickly. It does not publish a runtime for these models.
• Agility Robotics Digit: in a press release of 31 March 2025, Agility said the improved battery lasts up to four hours and that Digit can dock itself onto a charging station.

To put the G1 figures in perspective, multiplying 9 Ah by 54 V gives roughly 0.5 kWh. That is our arithmetic, not a Unitree figure, and the real usable energy depends on the nominal voltage and on how deeply the pack is discharged. Spread over about two hours, it implies an average draw in the region of a couple of hundred watts. A humanoid is, in effect, a powerful electrical appliance that never switches off while it is in use.

If you want to see which robots are available to hire and what their listed specifications are, the robot catalogue entry for the Unitree G1 is a typical starting point.

Why a walking robot uses so much power

A wheeled robot that stops moving uses very little energy. A humanoid that stops walking is still working. Its leg and hip motors must keep producing torque to hold the body upright, and the control system corrects its posture many times a second. Our explainer on how humanoid robots keep their balance describes that constant correction in more detail.

Several other loads add up on top of that:

• Motors under load: squatting, lifting, waving the arms or dancing all require high torque, and electric motors turn part of that power into heat rather than motion.
• Computing: onboard processors for perception, speech and motion planning run continuously, and more capable AI hardware generally draws more power.
• Sensors: cameras, depth sensors, lidar and microphones each take a share.
• Cooling: fans and cooling channels that keep motors, electronics and the battery within safe temperatures also consume energy.

The result is that a choreographed dance routine or repeated lifting drains a pack much faster than a robot standing at a stand greeting visitors. Manufacturer runtimes are usually stated without specifying the activity, so they are best treated as a rough indication rather than a guarantee for a particular show.

Why not simply fit a bigger battery?

Battery weight creates a loop that engineers cannot escape easily. A larger pack adds mass, a heavier robot needs stronger motors and more power to move and balance, and stronger motors add even more mass. Past a certain point, adding battery buys surprisingly little extra runtime.

Space is the second constraint. Writing in IEEE Spectrum in October 2026, Agility's Jonathan Hurst explained that the battery and its cooling take up about three quarters of the torso volume of Digit 5, a robot he describes as weighing more than 120 kg. A humanoid's body has to fit through doors and work at human scale, so there is only so much room.

The third constraint is chemistry. Today's robots use lithium-ion cells, and progress in how much energy each kilogram stores is gradual rather than sudden. The US Battery500 research consortium, hosted by Pacific Northwest National Laboratory, is working towards cells of up to 500 Wh per kilogram as a research goal, which indicates that today's commercial technology stores less than that. Even significant gains in cell chemistry would extend runtime incrementally rather than turn a two-hour robot into an all-day one.

Safety matters as well. A large lithium-ion pack inside a machine that can fall over must be protected against impacts and faults. Figure AI, for example, says the battery in Figure 03, announced on 9 October 2025, has protections at the battery management system, cell, interconnect and pack levels and is certified to the UN38.3 transport-safety standard.

Strategy one: swap the battery

The simplest way around short runtime is to replace the empty pack with a charged one. Unitree describes the G1 battery as quick-release and the H1 battery as quickly replaceable, which in practice means an operator can change packs in a few minutes rather than waiting hours for a recharge.

The next step is to let the robot do this itself. UBTech says its Walker S2 uses a dual-battery design and can swap its battery autonomously within 3 minutes at a swap station, choosing whether to swap or charge depending on task priorities. UBTech markets this as enabling round-the-clock operation, but it does not publish the capacity or runtime of an individual battery, and the 24/7 claim is the manufacturer's own.

Boston Dynamics took a similar route with the production version of Atlas, presented at CES on 5 January 2026. The company says Atlas will walk to a charging station and swap its own batteries when power runs low and then return to work. Boston Dynamics did not state a runtime per battery in that announcement.

Strategy two: charge very fast and often

The alternative is to keep the battery in the robot and top it up in short bursts. Figure says Figure 03 has charging coils in its feet and can step onto a wireless stand to charge at 2 kW, which the company presents as allowing near-continuous operation if the workflow includes regular charging stops. Figure does not publish the battery capacity or runtime on that page.

Agility has pushed fast charging further. According to Hurst's IEEE Spectrum article, Digit 5 runs for 90 minutes on a 9-minute charge, with the dock delivering 240 amperes at 48 volts and active cooling stopping the battery from overheating. That works out at roughly 11.5 kW, our calculation from the stated figures. These are figures reported for a new model rather than independently measured results.

Both swapping and fast charging trade runtime per charge for infrastructure: a dock or swap station, a suitable electrical supply and space for the robot to reach it. In a warehouse that is easy to plan. At a busy venue it is a design decision.

What this means for event organisers

• Plan in blocks, not days. Treat a humanoid as working in sessions of roughly one to two hours for demanding activity, with breaks for charging or a pack change. Our guide to battery life and charging during long events covers typical schedules.
• Ask how power is handled. When you compare offers, check whether the supplier brings spare batteries, how long a swap or recharge takes and whether a backup robot is included. The guide on comparing robot hire quotes like for like lists the questions to ask.
• Match the activity to the runtime. A dance show or carrying items drains a battery faster than greeting guests. Brief the supplier on what the robot will actually do.
• Reserve power and space. Charging stations and swap points need sockets and a discreet area backstage; include them in your venue checklist.
• Read runtime claims carefully. Self-swapping and fast-charging robots are mainly announced for industrial customers, and most event-ready models today still rely on human operators to change or charge batteries.

Frequently asked questions

How long does a humanoid robot battery last?

Published figures are usually a few hours. Unitree lists about two hours for the G1, and Agility said in March 2025 that Digit's battery lasts up to four hours. Many manufacturers, including Boston Dynamics and Figure for their latest models, do not publish a runtime at all. Real runtime depends heavily on what the robot is doing: dancing, lifting and walking use more energy than standing and greeting visitors.

Why does a humanoid robot use power when it is standing still?

Unlike a wheeled robot, a humanoid has to hold itself upright. Its leg and hip motors keep producing torque, and the control system makes continuous small corrections to stay balanced. The onboard computers, cameras and other sensors also keep running, and cooling fans may be active. So even a robot that appears idle is drawing a noticeable amount of power from its battery.

Can humanoid robots change their own batteries?

Some manufacturers say so. UBTech states that its Walker S2 can swap its battery autonomously within three minutes at a swap station, and Boston Dynamics says the production Atlas presented in January 2026 will walk to a station and swap its own batteries. These features are aimed at factory and warehouse use. Robots commonly used at events usually have quick-release packs changed by an operator.

Will better batteries soon make humanoid robots run all day?

Not quickly. Lithium-ion energy density improves gradually, and research programmes such as the Battery500 consortium are still working towards higher-energy cells. Because extra battery also adds weight that the robot must carry, better cells tend to extend runtime incrementally. For now, manufacturers rely on battery swapping and fast or wireless charging to keep robots working for longer periods.

How this article was made: written by the humanoid4rent editorial team with AI assistance; every factual statement was checked against the sources listed below on 2026-10-31. Spotted an error? Write to info@humanoid4rent.com.