Total cost of ownership is already at parity. Here is the maths.

Sticker price is the wrong lens. Over a realistic ownership horizon, the numbers are converging, in some use cases, they have already crossed.

The conversation about electric propulsion almost invariably starts and ends at purchase price. The electric option costs more, sometimes significantly more, than the diesel alternative at the point of specification. This is true, and worth stating honestly. What is also true, and stated far less often, is that purchase price is the wrong metric for this comparison, and using it produces a misleading conclusion.

Building the model transparently

A defensible total cost of ownership comparison requires explicit assumptions about usage profile, ownership horizon, and cost inputs. Any model that does not state its assumptions is arguing a conclusion, not a case. The assumptions that matter most: annual engine hours (and therefore fuel and maintenance costs); the diesel fuel price in the relevant cruising grounds (the European average significantly exceeds the global average); the servicing intervals and costs for diesel versus electric (the latter has essentially no consumable servicing requirement); and the mid-life replacement cost of a diesel engine, typically required at 3,000–5,000 hours and representing a significant fraction of the original propulsion cost.

A liveaboard or passage-making yacht running 300+ engine hours per year, a realistic figure for an actively-used cruising boat that motors in light airs and enters and leaves port under power, will consume roughly 1.5–2 litres per hour at typical cruising loads for a 50hp diesel. At current European marina diesel prices of €1.80–2.10 per litre, annual fuel costs for propulsion alone run to €800–1,200 or more. Over a ten-year ownership horizon, that is €8,000–12,000 before servicing or capital replacement.

"Any TCO model that does not state its assumptions is arguing a conclusion, not a case. State the assumptions, show the crossover, and own the conditions under which it holds, and does not."

The crossover analysis

Against that fuel cost, the electric system's charging cost, whether from solar, shore power, or regeneration, is substantially lower per kWh delivered than the equivalent diesel thermal energy. A system that charges predominantly from solar has a near-zero fuel cost for propulsion. Even shore-charging at European marina electricity tariffs is significantly cheaper per nautical mile than diesel. The servicing differential is unambiguous: a diesel installation requires annual oil and filter changes, impeller replacement, fuel filter servicing, exhaust manifold maintenance, and eventual injector and engine overhaul. An electric drive requires essentially none of these.

The honest caveat: the TCO case depends heavily on the specific usage profile. A yacht that motors rarely, a dedicated passage-racer that sails in all conditions and rarely enters crowded anchorages under power, will accumulate few engine hours and therefore few fuel costs. For that owner, the TCO crossover is further out. A liveaboard who uses the engine daily, in marinas, in light airs, at anchor running services, that owner's crossover is closer. The model needs to reflect the actual boat, not an average.

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