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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.


AC (inverter)

[personal note from secessus: Electrical appliances like crockpots are plentiful and cheap at thrift stores. Check the wattage on the bottom/label. Removable crocks are somewhat less important in a vehicle context since we have no dishwasher to remove the crock to.]

Note: instant pots typically require more power than vehicle-dwellers have on tapL

The 3qt model (mini)… draws less wattage at 700W versus 1,000W for the 6qt and 1,200W for the 8qt. – loveyourrv4) {the 10qt is 1,440w – secessus}

. See below for alternatives.

  • Normal sized crock pots typically take 125w-200w on HI and half that value on LO. Example: Example: Maximatic slow cooker (170w) and Courant 1.5qt slow cooker (120w) with WARM/LO/HI settings.
    Some mini crocks have only one setting around 60-75W. Example: Tru stainless 0.65qt mini crock (40W).
    Large5) domestic crocks can take 300w+ and also a lot of space.
  • mini rice cookers. Normal rice cookers run ~300w but some of the smaller travel ones use less. Example: Dash 200w 1L travel rice cooker (200w).
  • immersion (loop) heaters for AC are typically 300w although NOS6) versions can be found for 200w. Example: Norpro 559 immersion heater. (300w)

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)


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
typically oval
new old stock
positive to isolator, negative to chassis ground
food/cooking/excess_power.txt · Last modified: 2021/08/27 15:24 by frater_secessus