Want a hotel room but can’t be bothered to search the multiple reservation sites? The new breed of comparison sites, such as Trivago, Kayak and Travelsupermarket.com, promise to do the shopping around for you.

But a Guardian Money price check has found that no single site produces guaranteed best prices – and that travellers should check all three before buying.

Trivago is spending millions on a TV advertising campaign where a couple search for a room in Barcelona. “We compare over 100 websites to find your ideal hotel at the best price,” says the voiceover. But despite promising to find the best price, some of the comparison sites lead holidaymakers into paying significantly over the odds.

For example, we tested prices for a long weekend in Seville this September. Trivago found 14 websites offering rooms at the three-star Itaca hotel, and said the cheapest was Travel Republic, at £75 ($117) a night. Kayak listed eight sites offering rooms at the same hotel, and said the cheapest was OnHotels at £109 ($170) a night. TravelSupermarket did not list the Itaca. In other words, a traveller could pay 45% more using Kayak for the same hotel on the same nights.

In general, Trivago offered better value than the other two, but not in all cases. It said the best price for the four-star Isla Cartuja in Seville was £60 ($94) a night, after checking 22 websites, with Olotels named as the best value. But on Kayak, a search of 12 websites found a price of £52 ($81) a night, via HRS. TravelSupermarket said the best price for the Isla Cartuja hotel was at OnHotels, quoting us £61.50 ($96) a night. So in this instance, Trivago was 15% more expensive than Kayak, but a little cheaper than TravelSupermarket.

Sometimes the sites said rooms were sold out when they were available elsewhere. For example, Kayak and TravelSupermarket said that the Melia Sevilla was sold out for the dates we selected, but Trivago said it could find rooms at the hotel via Travel Republic.

Can travellers find better value by going direct to the hotel websites themselves, rather than the comparison sites? Industry insiders say the reservation sites take as much as 25% commission from the hotels, so it should be possible for the hotels to undercut the likes of Trivago and Kayak. Indeed, most hotel groups say they offer a “best price guarantee”. However, in our research, we found little evidence that this is the case. The Itaca’s own website wanted £117 ($183) a night (compared to £75 ($117) via Trivago) while the Isla Cartuja wanted £62.60 ($98) a night (compared to £52 ($81) at Kayak).

Many viewers of its ads might imagine that Trivago is completely independent from the sites it is searching. But in December last year travel site Expedia bought a majority stake for nearly £400m. It is a similar picture at Kayak, which was acquired late last year by Priceline Group for £1.1bn.

Priceline also owns reservation giants Booking.com and Agoda.com, while Expedia owns Hotels.com, Venere.com and Hotwire.com.

Both Trivago and Kayak told Money they operate entirely independently to their parent groups. Indeed, Money’s research found no evidence that Trivago pushes shoppers into Expedia or that Kayak takes people into Booking.com. But we found (admittedly on a small sample compared to the millions of rooms the sites book every month) that Trivago frequently led buyers into deals from the independent firms Travel Republic and Olotels, while Kayak took users into deals from OnHotels and HRS.

A spokeswoman for Trivago said: “We are in no special relationship with any of our partners and there are no ownership stakes. We do charge our partners when a user clicks on their offer from our website. All our partners are treated equally and we always show the best offers first – this does not change according to the partner.”

Kayak told Money: “We strive to show the total price, with an accurate reflection of taxes and fees. If suppliers can’t meet that standard for some components, we will exclude their results for that given element. We manage this process diligently, which may account for some of the differences you appear to have found. It is always our intention to show the lowest possible price, including taxes and fees to provide transparency for our users.”

The hotel booking business has been the subject of a major investigation by the Office of Fair Trading. It centred on allegations that Expedia and Booking.com were insisting on “rate parity” from hotel chains, which prevented competitive discounting. This week the OFT said real competition was, in reality, relatively limited. Booking.com and Expedia have now agreed to “relax existing restrictions” so that rival agents can provide discounts on room rates. But the threat of multimillion pound fines and penalties has been lifted, with the OFT saying it will close the investigation if the sites accept and abide by the agreement.

The new guidelines are likely to result in an explosion of loyalty schemes which will offer prices somewhere between current advertised rates and those available on “top secret” sites where the buyer only finds the name of the hotel after booking.

This article originally appeared on guardian.co.uk

Tags: kayak, trivago
Photo Credit: Hotel-comparison site Trivago found lower rates for the Hotel Itaca Sevilla (above) than Kayak did, a study found. Hotel Itaca Sevilla