Making a Power Budget For Your Camper Build

Hurah, You passed the Safety Quiz and you’re ready to start planning your Camper Conversion’s Electrical System!

The first step is figuring out your power requirements

  1. Make a list of everything thing you plan on using
  2. Add a column for how many hours per day you’ll use it
  3. Add a column for how many amps it consumes on average when on
    1. If you know watts and not amps, you can just divide Watts by voltage (12V for DC, 120V for AC). In other words (Watts / Volts = Amps).
  4. Multiple Amps by the number of hours you’ll use it per day to get a new column “Amp Hours / Day”
  5. Sum “Amp Hours / Day” for your total

Ours looked like this:

Hours / Day AC/DC Volts Watts Amps Amp Hours / day
2 phones 2 DC 12 4.2 8
laptop (3 hours) 3 DC (see note) 12 65 5.4 16
CPAP machine (no humidifier) 4.5 DC (see note) 12 80 (peak) 6 30
Eletrical Kettle (2x 10 min) 0.3 AC 120 1200 10 3
2x LED Interior lights 2.4 DC 12 10 0.8
Fridge (super efficient) 24 DC 12 65 4 (peak) 30
Misc 12V (Camera / Etc) 0.8 DC 12 30 2.5 2
2x Exterior LED Floods (2 hours) 2 DC 12 36 3 6
Total: 97
  • Notice anything weird?
    • “Why are the laptop and CPAP DC?”  Normally they would be AC, but we bought one of these so we wouldn’t have to turn on the inverter to charge the laptop or the CPAP.  Not only does the hassle of the inverter, it’s about 20% more efficient (more info here in our post about inverters).  If that doesn’t make sense go take our electrical safety quiz!Our needs end up being relatively modest at 105 Amp Hours / Day.
    • “Why did did you put 1200 Watts for your 1000 Watt kettle?” We’re running that through the inverter, so we have to plan for that inefficiency.
    • “Why don’t some wattages match the listed amperage?” Some of the wattages listed are peak, some aren’t.  The goal right now is figuring out capacity requirements, we’ll worry about load later when we’re sizing wires and fuses.
    • “Why don’t some of the Amp Hours match Amps * Hours / Day?” These are things that aren’t always-on (like the fridge).  It’s on 24×7, but it only draws power for a fraction of that time.

If you want to know the exact power requirements for an AC unit we highly recommend the kill-a-watt, it’s a great tool and can also help optimize your home electrical usage.  For DC We bought a unit like this that we’ll mount in our Camper Conversion to display current draw in real time.  Check out further posts to see how it goes!



Once you know your daily power requirements…

And after all that you should be ready to start drawing your Camper Conversion Electrical Diagram!

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