A fridge is the one thing most off-grid builds run around the clock. Wattonomy works out the solar and battery it really takes to keep one cold — then designs the whole system, with the wiring and parts to build it.
A real Wattonomy output — a fridge-only off-grid build
System
12 V
Battery
2.56 kWh
Solar
400 W
Inverter
MP 12/2000 120V
SmartSolar 150/351×
200W solar panel2×
Battery → inverter cable4×
Battery → inverter fuse1×
Wire & fuse sizes follow ABYC E-11 — each conductor carries its fuse and stays under a 3% voltage drop.
Built to ABYC standards
Gauge · fuse · volt-drop sized
Every spec sourced
A fridge runs day and night — it sets the whole system.
Because it never really stops, a fridge is usually the biggest single load in a small build. Undersize the battery and the food’s warm by morning; undersize the wire and you’ve got a hazard. Wattonomy sizes the bank, solar and every cable around continuous fridge use — to ABYC E-11.
What it takes to run a fridge
A typical 12V compressor fridge uses roughly 600 Wh a day. Here’s what that means for your system.
Daily energy
A 12V fridge draws around 600 Wh/day depending on size and climate — the figure everything else is sized from.
Battery
Enough LiFePO4 to ride through the night and a cloudy day without dropping below a safe depth-of-discharge.
Solar to replace it
Around 400W of panel in fair sun replaces a fridge’s daily draw with margin — more in poor sun.
Cables & fuses
Sized for continuous current and voltage drop, with the right fuse — to ABYC E-11.
What you walk away with — free
A full system sized to keep your fridge running — battery, solar, inverter
A real wiring diagram with cable gauges and fuses
Cable & fuse sizing with the voltage drop checked
A shoppable parts list, each line traceable to ABYC or Victron specs
Building it for real? Unlock the build binder.
Free gets you a safe, correctly-sized design. The build binder gets you the documents to build it right — and prove it's right.
Printable wiring diagram, yours to keep & tape inside the build
Full parts list, every line sourced
The volt-drop & fusing calculation trail — the "why" behind every spec
The build binder is a one-time unlock — no subscription, no auto-renew.
Questions
How much solar do I need to run a fridge?
A typical 12V compressor fridge uses about 600 Wh a day. In fair sun, roughly 400W of solar replaces that with margin; in poor winter sun you’ll want more, or a second charging source. Wattonomy sizes it from your fridge and climate, not a rule of thumb.
How many batteries to run a fridge overnight?
For a single 12V fridge, a battery around 2.5 kWh (roughly 200Ah at 12V) of LiFePO4 comfortably covers a night plus a cloudy morning. The tool sizes the exact bank from your fridge’s draw and how many days of backup you want.
Can solar run a fridge without a battery?
Not reliably — a fridge cycles day and night, so it needs a battery to carry it through darkness and cloud. Solar recharges the battery; the battery runs the fridge. The tool sizes both together.
Does this work for a 120V/240V fridge?
Yes — add a mains fridge as a custom load with its watts and hours and the tool sizes the inverter and bank around it. A 12V compressor fridge is far more efficient off-grid, though, and the tool will show the difference.
The standards we build to
Plain version: these are the recognized rulebooks your design is sized against, so the numbers hold up to a surveyor, an inspector or an insurer.
ABYC E-11The US standard for AC & DC wiring on boats — what a surveyor or insurer actually checks.
Wattonomy applies these standards in its calculations. It is not certified, sponsored or endorsed by ABYC, ISO, NFPA or Victron — it sizes your design to meet what they require, and shows the working.
Sized and checked to ABYC E-11. Last reviewed June 2026 — see the full methodology for the exact rules behind every number and how each design is validated.
Built by anABYC Certified Master Technician