12V reference charts
The tables you keep open while you build. Ampacity, voltage drop and fuse sizing figures follow ABYC E-11, which is the standard most vehicle and marine installations are held to.
<!-- gift-guides-xlink -->How to use these charts safely
Wire sizing is always two questions answered in order. Ampacity asks whether the conductor can carry the current without overheating, and the ampacity chart answers it. Voltage drop asks whether enough voltage survives the run to be useful, and the voltage drop chart answers that. On long runs voltage drop usually governs and the wire ends up larger than ampacity alone would suggest.
A fuse protects the wire, never the device. Size it at or below the ampacity of the smallest conductor in the circuit and fit it at the source of power, within a few inches of the battery terminal. The fuse sizing chart works through the common cases. Inside an engine space every ampacity figure derates by roughly 30 percent.
The load side charts turn appliances into amp-hours: appliance power draw, fridge draw by ambient temperature, solar output by sun hours and sun hours by region. Together those four are most of what the calculators do for you automatically.
All reference charts (9)
- Appliance Power Draw Chart: Watts to Amp-Hours at 12VTwenty-nine real 12V and AC loads with watts, amps at 12V, realistic daily run hours and daily amp-hours, split into always-on and... Open →
- Battery Chemistry Comparison Chart: LiFePO4, AGM, Gel and LeadLiFePO4 against AGM, flooded lead acid, gel and lithium NMC on usable depth of discharge, usable watt-hours per 100Ah, cycle life... Open →
- Fridge Power Draw by Ambient Temperature ChartDaily watt-hours and amp-hours for a 45 to 50 quart 12V compressor fridge at ambients from 60F to 110F, at both fridge and freezer... Open →
- Fuse Sizing Chart for 12V Overland and Van BuildsStandard fuse ratings matched to ABYC conductor ampacity from 18 AWG to 4/0, every fuse format from ATC blade to Class T with DC... Open →
- Peak Sun Hours by US Region: Winter, Summer and AnnualPeak sun hours for twenty-four North American regions with winter, summer and annual averages, the seasonal swing for each, and the... Open →
- Rooftop Tent Weight Chart: Tent Plus Rack vs Roof LoadRooftop tent weights by category with closed heights and setup times, the 25 to 90 lb of rack weight people forget, and every tent... Open →
- Solar Panel Output by Sun Hours Chart for 12V BuildsDaily watt-hours and amp-hours at 12V for arrays from 100W to 800W across 2 to 7 peak sun hours using the 0.75 real-world derate... Open →
- Voltage Drop by Run Length Chart for 12V SystemsPercentage voltage drop at 12V for every wire gauge from 18 AWG to 4/0, across run lengths from 5 to 30 ft, at 10A, 20A, 30A, 50A... Open →
- Wire Gauge Ampacity Chart for 12V Overland BuildsThe full ABYC E-11 copper ampacity table from 18 AWG to 4/0, inside and outside engine spaces, plus bundling derates, insulation... Open →
Electrical safety: a 12V system is low voltage but not low energy. Every circuit must be fused at the source of power, within a few inches of the battery terminal, at or below the ampacity of the smallest conductor it protects. Size cable for voltage drop as well as ampacity, and have any lithium installation inspected by a qualified installer before it carries load. Everything on this site is researched guidance, not an electrical certification.