Every sailor who hears “solar-electric” asks the same thing, and they’re right to ask it: what happens in a Pacific-Northwest winter, when the sun barely clears the trees and the days are short and grey? Here is the honest answer, without the brochure gloss.
First, what we have not done. Our thousand-mile proof was sailed in the summer and fall of 2024. We have not yet run a full winter passage, and we are not going to pretend a graph from July tells you what February feels like. When the winter data exists, it will go in this log, numbers and all.
What we can say is how the boat is built to behave when the sun is thin. SV Endurance carries a 1 kW array on a high-voltage 100 VDC bus and a 24.48 kWh propulsion bank at 48 volts. On a bright day the panels do the work; on a dark one, the bank is a reservoir you draw down slowly. The design assumption was never “the sun always shines” — it was “size the reservoir so a run of grey days doesn’t strand you.”
And the discipline that makes that work is a floor, not a full tank. Over the 1,000 NM trial the array harvested more energy than the motor consumed — the 48 V bank never fell below 50%. Half the bank is a safety threshold we hold to, not a number we chase to zero. In winter that floor matters even more: you plan the day’s run against what you actually have, and you keep the reserve deep.
The honesty valve
Ed puts it plainly: you can still keep a generator on board, purely for emergencies — or for the day you want to push through a six-knot chop with three knots of current against you. That candour is the point. This isn’t a promise that you’ll never plug in or never carry a backup. It’s a promise that on most days, in most conditions, you won’t need to — and that we’ll tell you exactly where the edges are.
The winter question doesn’t have a slogan for an answer. It has a bank size, a discipline, and a backup you’ll rarely reach for. If you want to see how those numbers land for your boat and your cruising ground, that’s exactly what the configurator is for.