In hospitals across the US, patients and staff have become accustomed to seeing a one-armed, four-foot high, friendly-looking white robot going about its business.

Nurses have been known to greet Moxi, as the robot is called by its maker Diligent Robotics, with a "good morning", a high five or even a hug.

Moxi – which shuttles medical supplies around hospitals – might respond by displaying its heart-shaped LED eyes and a beep beep greeting of its own.

"We get a lot of feedback that Moxi feels like a part of the team," says Todd Brugger, chief operating officer at the Texas-based robotics company, which has around 100 of the wheeled robots in operation.

But bringing Moxi into a hospital doesn't mean buying one of the machines outright. Instead, it is among robots available to rent or on a subscription basis.

Robotics companies use the term robotics-as-a-service. As well as the robot itself, service, maintenance and upgrades are bundled into the deal. A human engineer sitting in a remote control room may be on hand to take control of the robot if needed.

In Moxi's case, Brugger says: "It lowers the expense and the outlay for the hospital because you're not paying for the full purchase up front. Secondly, and I think more importantly, this tech is evolving very quickly… we're routinely evolving the software and capabilities of the robot."

Robot rentals are becoming available for anything from a day to years for a variety of purposes, from Moxi's hospital deliveries to robot bartenders or autonomous weeders for farms.

Increasingly this includes early humanoid models, designed to behave and look like humans, and operate in environments designed for people.

Given humanoids are still a work-in-progress, they are currently rented out for clearly defined tasks. That often means entertainment. Depending on the model, a machine might dance, sing or serve guests at a wedding or corporate event.

Ethan Qi, a Beijing-based associate director at Counterpoint Research, says an act like a humanoid dance routine is relatively simple to pull off.

"You hire a real dancer to perform and video it. The video is then used to train the robot. Then the robot will know how to dance. But the engineer will still often go with the robot in case the environment or the platform isn't simple," he says.

Renting allows buyers to keep up with rapidly changing tech

But ambitions for humanoid rentals go beyond the entertaining dance routines that are shared on social media, often in China. How about a robot housekeeper subscription?

California-based 1X plans to start shipping its home helper robot NEO later this year. "Early access" customers in the US can either pay $20,000 (£15,000) outright for their own robot, or $499 (£378) per month on a subscription basis.

Dar Sleeper, vice president of product and design at the company, says: "While many customers will buy a NEO outright, a subscription significantly lowers the upfront cost, making it affordable for far more people."

Part of the appeal of a rental over an outright purchase is the speed at which robotics technology is improving. If you splash out on a new humanoid now it is likely to soon be obsolete.

Qi says: "Every year the robotics companies release a new model, a new iteration of the hardware. If you own a robot, you can't trade it for a new one, but if you rent a robot, you can always rent the newest."

A rental also removes the need for deep technical expertise – you can simply take your problems to the manufacturer or rental platform. Qi says: "It helps to solve technical problems because customers don't know how to code the robots."

1X plans to offer its Neo robot for $499 per month

It's not just humanoids that are driving demand for robot rentals. One company, Chicago-based Formic, has a fleet of more than 250 industrial robots operating on a robot-as-a-service basis. "Everything is included," says Shawn Fitzgerald, chief revenue officer at Formic. "If the robot arm burns out, that's on us and we need to come bring you a new one."

He argues that Formic's flat monthly payment model "levels the playing field" for smaller companies that traditionally haven't been able to afford to buy factory robots outright. Formic is also currently testing humanoid robots for industrial uses.

Alongside flat rates, other robot rental payment schemes are emerging. Marco Wang, an analyst at Interact Analysis, says that some companies have started requesting that rental fees be directly linked to how much human labour a robot can save them.

For robot manufacturers, alongside the revenues, a rental scheme offers a way to trial their products in real-world scenarios and gather helpful data in the process. This is particularly important for humanoids: "The technology is still not there. It's still immature," says Wang.

Agibot robots are available to rent in 17 countries

Some firms in China – the early leader in humanoids and home to a growing number of rental schemes – have leased their creations to work in hotels, a helpful training ground for future domestic use. Others offer them to rent on cleaning service apps.

Chinese firms have started offering rentals overseas, through partner businesses. Among the biggest, Shanghai's Agibot says its humanoids are available for rent in 17 countries, including the UK.

However, while rentals are becoming more common, Shanghai-based Wang suspects outright humanoid purchases will dominate in China, encouraged by government incentives. He says: "There are a lot of humanoid robot orders from Chinese state-owned companies and a lot of orders driven by subsidies."

In China and elsewhere, some companies may also prefer to buy robots outright for the prestige, to learn from the technology or because it is better for their bottom line.

But for others, as robots become more sophisticated and the market grows, the convenience and affordability of a rental may be the answer.