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cooking with excess electrical power

Cooking and heating water with electricity off-grid is usually impractical but there are exceptions. In some cases the relatively large power loads can be used without affecting house battery1) state of charge:

  • while driving2) the alternator makes a great deal of excess power. Class C RV owners often run a crock-pot while driving from site to site.
  • if a generator is being run to charge batteries cooking loads can be added
  • with lead-chemistry batteries, later in the day excess solar power is available. The actual amount of excess power will depend on what your panels+controller can put out
  • with lithium batteries, power can be consumed at any time since Li doesn't need to reach full charge.


In general DC power3) is used for warming or very slow cooking. Part of this is due to the limits of cigarette lighter outputs, typically 120w (10A x 12v). The “catch-22” is that most people don't drive their vehicle sufficient hours to do real cooking off DC.

Higher power is common with AC devices but one must have the power to run it, and to recharge the battery bank afterwards.


  • heated lunchboxes/warmers are large enough to hold hot lunches. They are typically better suited to warming precooked meals rather than cooking from scratch. They come in “lunchbox” and “suitcase” styles.
    • lunchbox - hard exterior, typically better insulated tops and higher power.
    • suitcase - soft exterior, often lightly-insulated tops and lower heating power.
  • crockpot/slow cooker typically require many hours of cooking.

AC (inverter)

Analog cooking appliances (knobs, not electronics) run fine off inexpensive MSW inverters.

crockpot vs instant pot

Instant Pots are becoming increasingly common as some vandweller power systems become beefier. While convenient, they are effectively electric pressure cookers + crockpots, both of which are much less demanding of power.5)

Note: instant pots typically require more power than most vehicle-dwellers have on tap, but it can be done if one understands the issues.

The 3qt model (mini)… draws less wattage at 700W versus 1,000W for the 6qt and 1,200W for the 8qt. – loveyourrv6) {the 10qt is 1,440w – secessus}

Instant Pot advantages:

  • much faster cooking times possible
  • temperature control (heating element runs as needed)for more accurate cooking and reduce power consumption
  • better insulation will likely reduce power consumption
  • pressurized modes will result in consistent cooking at high altitude

Crockpot advantages:

  • much lower cost, particularly if bought used at thrift stores
  • much lower current demand (150w vs 1000w), which means a crock can run on components that cost 1/6th as much
  • analog crocks (physical controls, no digital components) run happily on inexpensive MSW inverters

also see this post

breaking the 10A barrier

Ciggy outlet power is typically limited to 10A (~120w).

If you wanted to extract more power from the alternator you could wire in an isolator (plain solenoid or VSR). Instead of feeding an auxilliary battery this isolator would be used to pull more current into the living area. You could run 12v loads directly, or attach an inverter's input wires to the isolator's outputs.7)

further info


Power/time saving

  • Preheating water on the dash or elsewhere
  • heating only the required amount of water
  • reducing power level after reaching a boils (ie, reduce power to simmer)
  • covering pots while heating
  • pre-soaking beans (overnight) rice (up to an hour), etc


  • use parchment paper, foil to line crocks
  • lightly oil crocks before cooking to reduce sticking
  • immersion heaters might best be used for heating plain water, as the loops can be difficult to clean


or starter battery
not idling
chassis power
new old stock
traditional pressure cookers are heated on the stove
positive to isolator, negative to chassis ground
food/cooking/excess_power.txt · Last modified: 2022/10/29 11:06 by frater_secessus