Key findings from the Ferrygogo analysis include:

• Next summer, a typical night ferry crossing for a family of four costs around GBP 930 in June and GBP 1,070 in August - often less than flying once hotel nights and car hire are included.
• The shortest Channel hops, such as Dover-Calais, are among the most expensive crossings per mile, you pay for speed and frequency rather than distance.
• The long overnight crossings from the UK to Spain (Portsmouth and Plymouth to Santander and Bilbao) offer some of the best value per mile of any route in the study.
• Sailing from Barcelona to Rome is cheaper per kilometre than sailing from Barcelona to Ibiza or Mallorca, as the Balearic routes carry a clear “island premium” per mile.
• On London - Rotterdam, a family flying with hotels and car hire pays around GBP 600 more than taking the Harwich toHook of Holland ferry – and emits roughly 380 kg more CO2.
• Shifting a ferry holiday from the first week of August to late June can often save between 15% and 20% on the same route.
• Night sailings are generally cheaper per mile and per person than day crossings, even though the ticket price looks higher at first glance.
• On several popular routes, families that choose the ferry over a short-haul flight cut their CO2 footprint for the main leg of the journey by roughly 50-75%.
• The Denmark–Iceland route is the most expensive crossing in the research in total cost, with four nights on board, yet it still isn’t the worst offender when you look at price per mile.
• Booking in November or early December, when early-bird and Black Friday deals appear, can shave up to 20-25% off next summer’s ferry crossings for a family of four.

The research compares shoulder season (late June) with peak season (early August) on dozens of routes between the UK, Ireland, France, Spain, the Netherlands and the Nordics. Short daytime hops such as Dover-Calais turn out to be among the most expensive crossings per mile, while long overnight routes from the UK to Spain offer some of the best value per kilometre. Surprisingly, sailing all the way from Barcelona to Rome works out cheaper per kilometre than taking the ferry from Barcelona to Ibiza or Mallorca, where an “island premium” pushes up the price per mile.

Beyond price, Ferrygogo also examined the climate impact of different choices. On routes such as London to Rotterdam, the analysis shows that a family flying with hotels and car hire pays around GBP 600 more than taking the Harwich to Hook of Holland ferry and emits roughly 380 kg more CO2 on the main leg of the journey. On several other popular crossings, families who opt for the ferry instead of a short-haul flight reduce their CO2 footprint on that main leg by roughly 50-75%.

The timing of a booking matters as well. By tracking fares in November and early December, when early-bird and Black Friday deals are launched, Ferrygogo found that families can often save 20-25% on the same summer sailing compared with booking later in the year. According to Ferrygogo, the data shows that night ferries may look expensive at first glance, but once distance, hotel nights, car hire and CO2 emissions are taken into account, they are often one of the smartest ways to get a family to their holiday.