Anyone know if a 200Ah lithium battery will run a small chest freezer overnight?

Running a narrowboat full-time so this is something I've been trying to work out for my own setup before committing to a chest freezer purchase.

The unit I'm looking at is a Shoreline 60L chest freezer — rated at around 45W but obviously it cycles on and off rather than drawing that continuously. From what I can gather, real-world consumption tends to be somewhere in the 0.5–1.0 kWh per 24 hours depending on ambient temperature and how full it is.

My current bank is a single Fogstar Drift 200Ah 12V LiFePO4, which gives me roughly 2.4 kWh usable (accounting for the 80% DoD most people seem to work to, though lithium tolerates deeper discharge better than lead). On paper that looks fine, but I'm not accounting for:

• Inverter inefficiency (I'm running a Victron Phoenix 12/375) — typically 85–90%
• Overnight being potentially 10–12 hours with no solar input
• Whatever else is pulling from the bank (bilge pump, 12V lighting, phone charging etc.)

So realistically, is a 200Ah bank actually enough for a freezer overnight without stressing the battery? Or am I underestimating the parasitic loads and the freezer draw, particularly in summer when ambient temps in the boat can get quite high?

Has anyone measured their actual chest freezer consumption with a Victron SmartShunt or similar, rather than relying on spec sheet figures? Real data would be far more useful at this point than theoretical calculations.

@AshChild ran a Shoreline on my tiny house setup for six months — 200Ah Fogstar Drift will handle it no bother, chest freezers are lazy things that barely cycle once they're cold, you're looking at maybe 30-40Ah overnight if it's not stuffed full of warm food 🧊

Lefty92 | 47 posts

Worth adding to what @RetiredElectrician74 said — the ambient temperature on your narrowboat will make a noticeable difference to how hard that compressor works. Moored somewhere shaded in summer versus a sun-baked towpath are very different scenarios. Also check whether the Shoreline has an eco mode; running it on that overnight can shave a fair bit off your consumption.

One thing I'd suggest before committing: borrow a plug-in energy monitor (Energenie or similar, dead cheap) and test the actual draw of the specific unit in-store or from someone who owns one. Manufacturer figures can be optimistic. Your 200Ah should be fine in most conditions but knowing your real numbers before you're living off it full-time on the cut is worth the extra legwork. 🙂

Been running a chest freezer on my boat for three years now, so here's the honest version nobody tells you:

Yes, 200Ah will technically handle it. But your first winter you'll spend every morning staring at your Victron BMV like it owes you money, convinced overnight the freezer secretly invited all its friends round for a party.

The

@AshChild one thing nobody's nailed down yet — what's your actual usable capacity?

A 200Ah LiFePO4 at 100% DoD is fine in theory, but Victron's own guidance (and most BMS specs) suggest staying above 10-20% for longevity. So realistically you're working with ~160-180Ah usable.

Also matters what voltage your freezer runs at. 12V compressor units draw less from the inverter path than running a 240V unit through an inverter, which adds ~10-15% conversion losses on top.

Worth logging your actual consumption with a Victron BMV or similar before committing — I did exactly this on my van before buying a freezer and was glad I checked first. The numbers surprised me.