Does refuelling your car class as parking? The answer appears to be yes if it’s an electric vehicle. Guardian Money has been contacted by several readers who were fined after charging their cars away from home.

The motorists report being caught out by signs that fail to make clear that charging points are subject to parking tariffs or to store opening times. Also, they have found some chargers being advertised as available for use when it would be a breach of the car park’s terms and conditions to use them.

Kevin Laban hoped his electric car would save him money as well as the planet. However, after he used a charger in a supermarket car park he received an expensive surprise. Through the post came a £70 parking charge notice (PCN) for using the service when the supermarket was closed.

The app operated by the EV charger operator Pod Point had directed him to a bay in an Aldi car park in Weymouth. Parking is not permitted on the site outside store opening times and, unbeknownst to Laban, EV charging is deemed to be parking by the landowner.

“Pod Point advertises the charger as open to the public, while the car park’s cameras are set to immediately fine anyone who enters to use it,” Laban says. “If the landowner does not want people charging outside store hours, the chargers must be deactivated, or the EV apps must sync with the parking restrictions.”

Laban says there were no signs in the car park, on the charger or on the app stating it could only be used during store opening times.

Aldi cancelled the PCN when Laban complained and insisted that car park terms and conditions are clearly displayed.

Pod Point told Guardian Money that landowners are responsible for notices about parking charges and restrictions displayed in its app and on site and while some prominently detail the relevant terms for EV drivers, others do not.

Laban’s experience exposes an anomaly in the rollout of EV chargers on private land: car park rules have not evolved to accommodate vehicles that stop solely to charge in a designated bay.

Another motorist, Clive Sanders*, paid more than he had bargained for when he charged his new EV in a Devon car park. He received a £100 PCN from the parking operator, Smart Parking, because he had only paid for charging. “There was no indication on the InstaVolt charger that I needed to pay the parking tariff as well as the charging fee,” he said.

“InstaVolt assured me they could get the PCN cancelled and gave me a letter to send to Smart Parking, but it refused to comply.”

InstaVolt said car park rules are set by the landowner and notices around its chargers warn that parking restrictions apply. It offered Sanders a £50 credit for the “inconvenience” after Guardian Money questioned the clarity of the signs.

“Parking terms vary from site to site and may refer to time limits rather than charges, so to tell drivers that ‘parking charges apply when charging’ would not accurately reflect the range of conditions that exist across our network,” a spokesperson said.

“That said, we do recognise that for drivers who are newer to public charging, the distinction between charging fees and site-specific parking terms may not always be immediately obvious.”

Smart Parking said it was up to drivers to check the terms and conditions before using the car park. “There is no free parking and motorists must pay for the duration they stay,” a spokesperson said. “In this case, the driver stayed for nearly an hour without paying for his parking, so was he correctly issued a charge.

Anthony Stone* was hit with a £100 PCN after using an advertised charger in a Holiday Inn car park without registering his number plate at the hotel.

“How many contracts should a driver be expected to enter to charge a vehicle?” he said. “I understood that I was contracting with the charger operator to provide electricity, but it seems I was also entering one with the hotel or its parking operative.”

A spokesperson for Holiday Inn said vehicles are identified by ANPR cameras that do not distinguish between parking and charging. It claimed that the display screen tells drivers to register their cars for free parking before charging. It agreed to cancel the PCN after Guardian Money got in touch.

PCNs for charging are an increasing problem for EV drivers, according to the motoring group the RAC. “Signage needs to be clearer, so drivers realise straight away whether they need to pay for parking, how long they can stay to charge and the hours of operation,” said its head of policy, Simon Williams. “Equally, charge point operators should add a warning to their devices and apps to make drivers aware.”

The Ministry of Housing, Communities and Local Government said that private car parks are governed by contract law and that tariffs for using EV chargers must be clearly displayed. It said it plans to publish a new code to raise standards for private parking later this year.

* Names have been changed

As the escalator descends below ground at King’s Cross St Pancras station in London, the shift from what was already a hot station entrance to the furnace-like subterranean depths is perceptible.

On the tube it’s worse: a man leans back in his seat, eyes closed, sweltering; people hold electric fans an inch away from their faces. London commuters are known for their stoicism and the heat appears to be another tribulation to accept. They will need to: heatwaves in the capital are becoming routine.

“We’re quite lucky that this platform is almost empty, because when the platform gets packed it’s [like a] sauna,” Anna, a passenger at Oxford Circus, says. “When it’s peak hours, it’s quite difficult.”

Anna says she usually adapts well to hot temperatures, but even she finds the heat on the platform hard to bear. Craig, another passenger, says he has to travel in gym clothes and change into his work clothes at the office because of the heat on the tube.

London’s underground isn’t adapted for the 30C+ heatwaves that have hit the city over the last few summers. Lines such as the Victoria line – the deepest on the network – and the Bakerloo line – which TfL says has some of the oldest trains in passenger use anywhere in the country – are particularly bad when it comes to withstanding the heat.

Sharmin, a barista at the Pret a Manger stationed by the barriers at King’s Cross St Pancras, says she has seen people faint in and around the station. She finds the heat so oppressive that she has asked to go home early during some of her shifts this week. She wonders why there are no coolers or industrial fans set up near Pret or the barriers. “I’ve felt like I was going to faint,” she says.

A quick glance at the thermometer I’m carrying on this unscientific investigation shows that the station is about 30C. On the platform and tube it crawls up to 32C, and then at the Victoria line platform at Finsbury Park it hits 34C. In the UK, it is illegal to transport cattle above 30C; transporting people at 34C, though, might be becoming the norm.

It’s ten degrees higher underground than it is outside at this point, according to my iPhone’s built-in weather app. Between 8am and 9am the thermometer shows readings of 34C on the Victoria line platforms at Finsbury Park, on the Victoria and Bakerloo line platforms at Victoria, and on the northbound Bakerloo line platform at Oxford Circus.

Asher Minns, executive director of the Tyndall Centre for Climate Change Research, a partnership across several UK universities, says that tube tunnels are “basically radiators”, taking on the heat of the clay and concrete around them. The carriages, platforms and surrounding tunnels are also warmed by the hundreds of kilowatts of heat the trains produce while breaking. And the warmer it is outside, the worse it gets underground.

But Minns adds that the infrastructure is difficult to adapt because of its age and the surrounding clay. It will likely be years before the network is better suited to dealing with the heat, so for now he says the focus needs to be reducing risks to passengers.

“It can’t go on like this, and it’s not going to get any better,” he says. “[The underground] absolutely has to adapt to the impacts of climate change, but right now I think [the focus] has to be looking after passengers.”

He suggests limiting the number of passengers allowed to travel when the temperature is above a certain limit, or reducing the number of tubes in service during heatwaves.

Nick Dent, TfL’s director of customer operations, said TfL was continuing to invest in making the network more resilient and comfortable as hotter summers become more common, as well as introducing new air-conditioned trains on the Piccadilly line and DLR.

Dent added that the “short-term and stop-start nature of funding over recent years has meant that TfL has had to carefully prioritise its investment and – while remaining open to measures that will help manage the impact of increasing temperatures due to climate change – has focused on programmes that will see the biggest benefits to customers”.