Carnival’s Biggest Efficiency Gains Start With Smarter Hotel Systems

An empty show lounge can recirculate air it has already cooled instead of continuing to cool outside air. That is a small operating change, but it captures what Carnival is getting right about ship efficiency. I’d give this kind of work more attention: cutting energy demand without asking passengers to accept a less comfortable cruise.

Carnival’s largest efficiency contribution to date has come from its Power Saver Packs, which target hotel operations, particularly air conditioning. The company is now pursuing expanded waste-heat recovery after reaching its 2030 greenhouse-gas target five years early. Its new goal is a 25 percent reduction in emissions intensity by 2029, measured against 2019.

Across Carnival’s existing fuel-efficiency measures, the company is on course to save approximately $650 million in 2026 compared with 2019. That figure covers the broader efficiency effort, not just the hotel-system upgrades.

Better controls, not warmer cabins

The Power Saver Packs combine improved heating, ventilation and air-conditioning controls with more efficient chillers and pumps, automated ventilation, LED lighting and energy monitoring. Carnival estimates ship-level fuel savings of about 5–6 percent once the packs are fully implemented.

“It's still the exact same amount of cooling, the same comfort level,” Marcel Goncalves, Carnival Corporation’s vice president of decarbonization, told Cruise Industry News.

That distinction matters. Reducing a ship’s energy demand by controlling equipment more intelligently is a better proposition than simply asking it to do less. Carnival says the expanding program has reduced annual shipboard energy demand by more than 535,000 MWh compared with 2019.

The empty show lounge is one example of systems responding to actual demand. Sensors provide readings every three seconds, Goncalves said, with multiple data streams combined into operating metrics that reveal more than individual measurements can.

“The physical equipment is already there, but you have to upgrade the brain,” he said.

The next opportunity is heat that ships already produce

Carnival now wants to recover more of the energy ships lose as heat and put it to work generating electricity, providing cooling and supplying onboard services.

“Of the energy in the fuel, about half of it's used, half of it's not,” Goncalves said.

Waste-heat recovery is already used aboard cruise ships. The opportunity is widening because newer equipment can generate power from lower-temperature hot water, rather than depending on high-temperature steam. Recovered heat can also serve domestic hot-water systems and spa facilities.

Organic Rankine Cycle equipment is one option. It can generate electricity using engine cooling water at approximately 75–100°C.

I like the logic of extracting more work from fuel already being burned. But the amount of unused heat is only the starting point. Engines operating at lower loads produce less available heat, and recovery equipment needs machinery space and maintenance. There also has to be useful onboard demand for the energy it delivers.

Those constraints make this an engineering decision, not an automatic win. The hotel-system program offers a useful standard for the next investment: a demonstrable reduction in what the ship needs to consume.

Smaller changes are adding up

Carnival has also upgraded turbochargers and camshafts during scheduled engine overhauls. Goncalves said improvements of a few percentage points per engine translate directly into lower fuel consumption and greenhouse-gas emissions.

Changing the sequence of destinations has reduced sailing distances and required speeds. Separately, 13 ships now have air lubrication systems, including new Carnival Cruise Line ships whose hull designs suit the technology despite their shorter Caribbean itineraries.

Demand forecasting is contributing beyond fuel efficiency. Food waste per person fell 47 percent in 2025 compared with 2019, approaching Carnival’s 50 percent reduction goal for 2030. Goncalves said forecasts account for passenger demographics, including the greater number of families and children sailing during summer.

LNG commitments need a different test

Carnival operates 11 LNG-powered ships, representing approximately 21 percent of fleet capacity, with seven more on order through 2033. Goncalves said the company is already using bio-LNG for part of its European operations and continues to evaluate methanol.

He described fossil LNG as the lowest-greenhouse-gas fossil-fuel option and argued that fossil methanol would increase emissions compared with diesel. Those comparisons depend on how the fuels are produced and which emissions are counted.

On a well-to-wake basis, LNG’s performance depends on upstream methane leakage, liquefaction and unburned methane released by engines. IMO lifecycle accounting includes carbon dioxide, methane and nitrous oxide across production and onboard use. Fossil methanol’s lifecycle emissions also vary by feedstock, while renewable methanol can deliver substantial reductions through low-carbon production pathways.

“With LNG, we see a clear pathway to bio-LNG and to e-LNG,” Goncalves said.

A pathway still needs to be delivered. That is why I put more weight on Carnival’s documented reductions in energy demand than on the promise of a future fuel transition. Every unit of energy a ship no longer needs is one less unit that transition has to supply.