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This blog post is going to be a step-by-step guide on how to perform a power audit so you can ACCURATELY size your camper solar system based on YOUR own power consumption to determine how many batteries you need for your camper van electrical system.

Quick note before we get started.  This is just one part of a overarching “How to Install a DIY Camper Van Electrical System” series.  If you’ve just stumbled on this article directly without seeing that, there are likely some things we’ve already covered.  If you want to check out that step by step guide, you can do that here: https://www.explorist.life/diy-campervan-solar

Also, we have interactive solar wiring diagrams that are a complete, A to Z solution for teaching you exactly what parts go where, what size wires to use, fuse size recommendations, wire lug sizes, and all kind of other stuff to help save you time and frustration.  You can check that out here: https://www.explorist.life/solarwiringdiagrams/

How to Size Your Camper Van Electrical System

You NEED to know how much power you use on a daily basis to determine the size of solar system you’ll need to power your camper.

Sure, you can buy a random solar kit and go for it, but more often than not, that tends to lead to disappointment in the performance of the system.

Be warned: This is an involved process. You’ll need to gather the items that you will be using (or look up their power usage) and put some numbers into the following spreadsheet you’ll need to download. After you’ve followed the step-by-step guide in this blog post, you’ll have a highly educated estimate of how much power you anticipate using throughout the day. This will give you a great baseline to determining how big of a camper solar setup you’ll need.

Step-by-Step Power Audit

What Appliances Will you be Powering?

You will need to gather as many of the items you will be powering.  If you don’t physically have the items yet, you will need to look up their power consumption rates (or use the ones I have pre-filled in for you).

Not all Appliances are the Same

There are AC appliances, DC appliances, and DC components disguised as AC components.  Confusing, I know. Hang with me, I’ll break it down.

AC Appliances

These are items that you plug into your normal household plug.  These will be items like a Coffee Maker, Instant Pot, Blender, Induction Cooktop, and a Vitamix.

TAKE ACTION: Gather all of these items into one pile and put a sticky note with “Table 1.1” next to them.

AC Appliances go in pile “Table 1.1”

*But wait…there is a catch…*

DC Appliances disguised as AC Appliances

There are imposters in your ‘AC Appliances’ pile.  There are likely items that plug into a normal household plug, that are actually DC appliances.  These items are like Computers, video game consoles (xbox), Cricut Die Cut machine, and printers.

A computer is a DC appliance disguised as an AC appliance.

How to Identify these imposters:  These items will have a ‘Wall Wart’ or an inline power supply AC/DC power adapter.

TAKE ACTION: Segregate these items into their own pile and label with a “Table 1.2” sticky note.

Inline power supply adapter commonly found on laptops
A wall wart converts 110v AC power to something usually in the 5v-20v range

DC Appliances

These items will be wired directly to your DC Distribution block (Fuse Block).  These will be items like 12v light strips, 12v puck lights, 12v fans, Maxxair Fans, Water Pump, and 12v TV.

TAKE ACTION: All of these items get their own special pile.  Label it with “Table 1.3”. “Table 1.3”.

DC Appliances power supplied by a 12v distribution block

Single Charge Items

These will be items like Phones, Camera Batteries, Drone Batteries, External Charger Packs, Etc.. Basically, anything you charge up, then unplug to use.

TAKE ACTION: Put these items in a pile and sticky-note it “Table 1.4”

Single charge items with replaceable like cameras and drones

Full Day / Per Day use Items

These are items you will let run ‘all day’.  12v refrigerator that cycles off and on, Weboost 4g booster, hot water heater are a few examples.

*Note, The list is pre-populated with a few items for you to use as benchmarks, but if these items have already been accounted for in a previous table, there is no need to add them here.

*Note, The refrigerator listed in the pre-populated list is the ARB 65qt and most top loading 12v refrigerators will have similar electrical demands.

*Note, the hot water heater is a delicate calculation.  The figure pre-input into the spreadsheet is for a 4 gallon Bosch hot water heater unit.  It uses about 65 Amp hours to heat up, then it holds that heat for 12 hours-ish.  The “Quantity” on that would be for “How many times do you plan on heating up 4 gallons of water”.  Use this as a benchmark, but not a rule*

TAKE ACTION: These items go into yet another pile. Label it “Table 1.5”.

Performing a Step by Step Solar Power Audit

Now you have your 5 separate piles labeled with Tables 1.1 – 1.5, we are going to go through them, pile by pile, item by item and input the ACTUAL numbers to get you as close as you can get to a PROPER educated guess that will tell you how much solar power you will need based on how much power you use every day.

For all of these items you will need either watts and volts *OR* amps, *AND* a rough approximation of how many minutes per day you anticipate using the device.

Now, you’ll need the spreadsheet your downloaded earlier. (It was toward the top of this blog post)

Table 1.1 | 110v Appliances

Look for a plate on the device that tells you how many watts the appliance uses.

  1. Change the name of the Item as Necessary
  2. Input the Watts into column 2.
  3. Input the number of minutes you anticipate using the item per day.

Your spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Example:

Input 110v Watts and Minutes used per day into Table 1.1

Table 1.2 | AC/DC Adapter Appliances

Look for a sticker on the wall wart or AC/DC Converter that tells you how many amps and volts the is on the Output side of the cord. It’ll look something like this: 

Input DC power values into table 1.2


Your spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Table 1.3 | DC Appliances

DC powered appliances typically hide their power usage for some reason.  If you look for a label or sticker with no success, usually looking online is the best option. You’ll be looking for the wattage of the device to insert it into column 2. If you find the amps and volts of the device instead, no worries!  Table 1.3 has a built in Amps to Watts calculator. Input your amps and volts into their appropriate spot in table 1.3, look at the resulting wattage reading, and insert that wattage reading into Table 1.3, column 2 under ‘Watts”.  Change column 5 to represent how many minutes you plan on using this device.

Input watts & quantity of DC appliances into Table 1.3

Your Spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Table 1.4 | Single Charge Items

For Table 1.4, you will:

  1. Change Column 1 to the Device Name.
  2. Change Column 2 to the Battery Size of the Device.
  3. Change Column 3 to the number of times you plan to charge the device per day.
If given Wh (Watt Hours) input into Table 1.4a
If given mAh (Milliamp Hours) input into Table 1.4b


Your Spreadsheet has been pre-populated for popular appliances and power outputs.  If your needs vary, alter as necessary by altering the GREEN columns. If you anticipate NOT using an item, you can delete the values in all of the GREEN columns, or simply input ‘0’ into the ‘Minutes Used Per Day’ Column.

Table 1.5 | Full Day / Per Day Usage

Table 1.5 is for items that get used CONSTANTLY.  You’ll have to take a constant measurement of your items over the course of 24 hours.  This is good for things that cycle off and on like a refrigerator. The pre-populated ‘Refrigerator’ option is based on a top loading ARB 50qt 12v Refrigerator.

TOTAL: How Much Solar Power Do I need?

Now that you have filled in ALL the blanks with the electrical items you anticipate using throughout your normal day, check out ‘Table 1.6’.  This is how many Amp Hours you will PERSONALLY consume per day according to all of your inputs as well as a recommendation for battery bank size, solar array size and a few other goodies:

Your Camper Solar Results

The numbers you see are just general recommendations. Want to spend more time in cloudy environments? Maybe you should consider sizing up a bit. Budget can’t handle your recommended components? Perhaps size down (but PLAN for expansion). These are all just general recommendations that I feel confident in recommending. Any more is better. Any less is on you.

Now that you know how much battery capacity you need in your camper van electrical system, now it’s time to decide if you want to play the short or long game and go with AGM batteries or Lithium Batteries.  Check out our comparison here: https://www.explorist.life/choosing-a-solar-battery-bank-for-a-camper/

Everything that you are learning here is put to use in our FREE Interactive Solar Wiring Diagrams.  If you haven’t yet, check them out as they are a complete solution for a camper van electrical system.  Check them out here: https://www.explorist.life/solarwiringdiagrams/

Remember, this is just one part of a full camper van electrical educational series.  To see all of the individual guides, click here: https://www.explorist.life/diy-campervan-solar

Finally, If you found this guide helpful, It’d truly mean the world to us if you’d share it with somebody who can use it, pin it to pinterest for later reference, or share it to a facebook group when somebody has a question about this subject.  Click the bubble in the lower right corner to subscribe to be notified of future updates and as always, leave any questions you’ve got in the comments below.