Made with in our van.

Sharing this tool with others is the best way to say thanks if you found it useful. Thanks for supporting us and for keeping this website alive! See you on the road 🙂

Disclosure: This post contains affiliate links, which means that if you click a product link and buy anything from the merchant, we will receive a commission fee. The price you pay remains the same, affiliate link or not.

Isabelle and Antoine
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Van Electrical Calculator

  • Size your battery bank, solar, alternator, shore & inverter automagically or manually.
  • Hover / tap any underlined wordUseful Tooltip! to reveal a useful tooltip.
  • Start with our Electrical System Guide if you're new to this!
12V DC
LOADName of the appliance. CUR
(A)AVERAGE CURRENT (in amps) drawn during operation. Find this info on Google, product's website, owner's manual, technical sheet.
(h)How many HOURS per day this appliance is in operation. It's a guesstimate.
(A)AVERAGE CURRENT (in amps) drawn during operation. Find this info on Google, product's website, owner's manual, technical sheet.
(h)How many HOURS per day this appliance is in operation. It's a guesstimate.


120V AC
LOADName of the appliance. PWR
(W)MAX POWER (in watts) of the load. Find this info on Google, product's website, owner's manual, technical sheet.
(h)How many HOURS per day this appliance is in operation. It's a guesstimate.
(Ah)[(POWER/12) x HOURS] / 0.85
INVThis column is used to size the inverter. Check all the appliances that you plan on using simultaneously. Note that the biggest load is automatically selected by the calculator. PWR
(W)MAX POWER (in watts) of the load. Find this info on Google, product's website, owner's manual, technical sheet.
(h)How many HOURS per day this appliance is in operation. It's a guesstimate.
(Ah)[(POWER/12) x HOURS] / 0.85
INVThis column is used to size the inverter. Check all the appliances that you plan on using simultaneously. Note that the biggest load is automatically selected by the calculator.


Battery Type

Your Type


1- Size Your Main Components
Use the calculator above
Daily Energy Usage

? Ah

Battery Bank

? Ah

Solar Panels

? W

Solar Charger


Alternator Charge

? A

Shore Charger

? A


? W

Manual Mode Enabled.
Bold options = automagic values.
2- Size Your Wires, Fuses & Breakers
+ Wire Lengths & Terminals Calculator

Appropriate wire gauge (AWG) varies with length & load and therefore is unique to each installation. Our wiring diagram automatically sizes the wires gauge, fuses & breakers to ensure that your own system is safe and performs as it should. Bonus: it also calculates all the wires lengths & terminals that you'll need by type/gauge, which will make STEP 3 (customize your items list) super easy to complete. No other diagram does this!

3- Customize Your Items list

Fill these tables per your wiring diagram:




Cost EstimateIncludes everything on your Items List, except the 12V & 120V loads (appliances) and Tools. Prices on Amazon change frequently, so our estimate is subject to change.


Items List

The list below defines your entire electrical system. Click on "ADD ITEMS TO AMAZON CART" section-by-section; make sure that all the items are valid (links to Amazon products sometime change, please let us know if that's the case!) and make sure all items are in stock at the moment.

# Item Description Quantity View on Amazon
1 Terminal Fuse, 250A Blue Sea (Catastrophic Fail Safe) 1 View
2 Terminal Fuse Block Blue Sea (Connects directly to battery post. Holds the Terminal Fuse) 1 View
3 System Switch Blue Sea (Main System Switch) 1 View
4 Bus Bar (250A, 4 studs) Blue Sea 2 View
5 Cover for Bus Bar (for 250A 4 studs) Protect the Bus Bar 2 View
6 40A Breaker/Switch, Surface Mount Between Fuse Block and Bus Bar 1 View
7 Fuse Block (12 circuits) Blue Sea (12V Distribution Panel) 1 View
8 Fuses Kit Assorted Fuses (2A 3A 5A 7.5A 10A 15A 20A 25A 30A 35A) 1 View
9 Battery Monitor Victron BMV-712 with BlueTooth 1 View
#ItemDescriptionQuantityView on Amazon
1Heat Shrink Butt Connector, Ancor MarineTo connect to Loads (75 Pack Kit)1View
2Heat Shrink Disconnect, 10-12 AWG Cable, 1/4″ Tab, Female
To connect to certain loads (i.e. 12V Sockets) , to make “removable” connections (i.e. Fridge, LEDs) and to connect cable of different gauge together (i.e. LED Dimmer) (25 Pack)
3Heat Shrink Disconnect, 10-12 AWG Cable, 1/4″ Tab, Male1View
4Heat Shrink Disconnect, 14-16 AWG Cable, 1/4″ Tab, Female1View
5Heat Shrink Disconnect, 14-16 AWG Cable, 1/4″ Tab, Male1View
6Heat Shrink Disconnect, 18-22 AWG Cable, 1/4″ Tab, Male1View
73M Scotchlok Quick Splice with Gel (14 AWG stranded)We used that to parallel our LED lights (25 Pack)1View
8Split Loom Tubing, 3/8″ diameter 20 feetTo protect wire bundles1View
9Split Loom Tubing, 1/2″ diameter 20 feetTo protect wire bundles1View
10Split Loom Tubing, 3/4″ diameter 20 feetTo protect wire bundles1View
11Nylon Cable Clamps KitTo secure cable/split-loom to wood1View
12Zip Tie Mount with AdhesiveTo secure cable/split-loom to metal1View
13Nylon Zip Ties KitTo secure cable/split-loom1View
14Rubber Grommet KitTo protect wire from sharp edge (going through metal hole)1View
12V Loads

These are the appliances we personally use in our van:

# Item Quantity Buy Link More Info
1 Maxxair 6200K Roof Fan 1 Amazon Fan Installation
2 LED Ceiling Lights (Dimmable) 3 Amazon
3 PWM Dimmer for LED Lights, 12V, Slider 1 Amazon
4 Blue Sea 12V Socket 4 Amazon Electrical System Guide
5 Shurflo Revolution Water Pump, 3 GPM 1 Amazon
6 ON/OFF Switch for Water Pump 1 Amazon
7 Webasto Air Top 2000 STC Gasoline Heater 1 eBay Webasto Installation
8 Propex HS2000 Propane Heater 1 Dealers Propex Installation
9 Novakool R5810 Fridge, 12V only 1 Novakool Fridge Guide
10 Sirocco ii Gimbal Fan, 12V 1 Amazon Sirocco ii Installation / Review
11 Nature’s Head Composting Toilet 1 Amazon Toilet Installation
12 Propane Solenoid Shutoff Valve 1 Amazon
13 ON/OFF Switch for Propane Solenoid 1 Amazon

These are essential to build your electrical system. Do NOT cheap out on tools (e.g. using pliers to crimp) or you'll compromise the performance and safety of your system.

# Item Description QTY View on Amazon
1 Crimping Tool, Single-Crimp (8-22 AWG) Single-Crimp should be used with Heat Shrink connectors to prevent tearing the insulation and loose the watertight connection (corrosion prevention) 1 View
2 Cutter / Stripper for 10-22 AWG Stranded Wire Nothing to add! 1 View
3 Hydraulic Crimping Tool (2/0-12 AWG) Provides adequate, repeatable results for larger gauge lugs. 1 View
4 Cutter for up to 4/0 Cable For large gauge cables 1 View
5 Heat Gun for Heat Shrink Connectors 1500W, Dual Fan Speed, Variable Temperature Control 1 View
6 Digital Multimeter (Voltage, Current, Continuity, Resistance) You don’t need it until you need it! Your friend when you need to troubleshoot… 1 View


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about us

Nice To Meet You.

Hello! We’re Isabelle and Antoine 🙂 In 2017 we sold our house (and everything in it), quit our engineering careers and moved into our self built campervan. We’ve been on the road since then and every day is an opportunity for a new adventure; we’re chasing our dreams and hopefully it inspires others to do the same!

39 thoughts on “Van Electrical Calculator”

  1. Does your calculator design the electrical system based on a 4-day off-grid timeframe? I ask this because you mentioned that your goal was 4 days off-grid. What % of that time is assumed using the alternator?

  2. Hi,

    Would love to buy the electric wiring module but am wondering whether this also works for 220V (EU) and does it have links to EU products?


  3. Bonjour Antoine!

    Tout d’abord, merci de partager toutes ces infos, c’est très apprécié.

    J’ai reçu un panneau solaire de 275w d’un ami et je compte l’utiliser pour mon camper van. Cependant, le wattage est un peu haut pour mes besoins énergétiques; votre calculatrice solaire me recommande plutôt 175w. Je me demande seulement si c’est sécuritaire d’utiliser le panneau avec une batterie plus petite, disons 100ah?

    Je planifie acheter AGM 12V, avec un contrôleur de charge MPPT.

    Merci beaucoup!

    • Pas de souci, ca devrait être correct. Faite passer le calculator en mode “MANUEL” et choisissez 100AH AGM comme batterie et 200W comme solaire (ou plus); si il y’a un problème, un message s’affiche dans la section “DIAGNOSIS”.

      Bonne chance!

  4. Antoine,

    Thanks for all your work on this site. It’s been a tremendous resource.

    The guide on this page recommended lithium batteries and the samlex SEC-UL battery charger for shore power. The product description for the charger does not mention its compatible with lithium batteries however. Do you see any issue with using this combination?


    • Lithium can be charged with AGM settings, since the voltage profiles are the same:

      “You can use any standard charger, solar or wind charge controller to charge our LIFEPO4 deep cycle battery. There are some chargers and controllers that are programmable to get full usage out of your battery, but most will have an AGM setting which normally bulk charges about 14.4 volts and floats at 13.6 volts. These levels are great for your Battle Born battery.”


  5. Salut Antoine,

    First, this site is amazing and so is your FB Group. I’m learning all the basics here, but I’ve been told to go another route and purchase directly on AliExpress (Ex:,searchweb201602_,searchweb201603)… Seems alot cheaper, and good stuff… What do you guys think?

    • You get what you pay for; cheap and good rarely go well together. I always recommend to go for branded products, backed up by a warranty and customer service. Especially for critical components such as the electrical system where safety counts.

  6. I feel like I’m in electrical boot camp. Trying to synthesize all the information related to van system. I’m starting to understand how it all fits together but 2 questions for today. What are the terminal fuses and main switch functions in the faroutride wiring diagram and is this something needed in our simpler set up? Diagram in facebook post (DIY Cargo Van Conversion Help | Campervan Builders Forum) 5.20.20

  7. Thank you for creating all this information! Massive help. I am working on sizing wires through the blue seas app. As a means of understanding and checking things, I have plugged in some of your info from your build. I can’t get it to size the wires you listed.

    Example – Your fan – .3A @20hr at 30ft recommends 18 awg wire. You used 14 awg. ( I have tested several of your other scenarios and can not get the gauge to be similar.

    Am I plugging something in wrong, or is there a different wire size calculator used? Thanks.

    • It is not really recommended to use 18AWG as it is weak (because of the small diameter). Then, the next size would be 16AWG… but we choose 14AWG, so we don’t have to order too many different size of wire (to save $$$). It is totally acceptable to use bigger wire than needed (but it’s not acceptable to use smaller one).

      Hope that helps!

  8. Excellent website! I appreciate you guys sharing all of your knowledge and troubleshooting!!
    One question I didn’t see anywhere else (maybe I missed it). How did you get your wire from alternator to battery? Under van in conduit? Inside van under flooring? Thanks!!

  9. I’ve got two questions.

    1. What is your take on charging equipment that uses 5v? For instance, the wifi-extender we are planning to use is 5vdc.
    2. Do you have a way to limit ‘vampire drain’ but shutting off sections of your system overnight? I just don’t see the sense in letting something like a wifi-extender drain power, even in standby mode, while I’m sleeping.

    • Hi!
      1. I would use a 12V to 5V converter:
      2. We don’t have any appliance that stays on stanby (except maybe the JetPack, but we turn it off at night. Oh and the SensorPush Gateway as well, but I don’t really worry about that…), but adding a switch to a section of your system would definitely works!


  10. Hello!

    This 3 part electrical series has been so helpful in wrapping my head around this as a total beginner, so THANK YOU! I’ve created my own diagram based off of yours and I have one question. Did you include a ground? I’ve seen it connecting at the negative bus bar, but I’ve also read some contradicting opinions. Any help would be much appreciated.

    Thank you again!

    • The ground it the connection between our Negative Bus Bar & the van chassis (see If you don’t charge from the alternator, you don’t need to ground to the vehicle chassis!

  11. Antione.

    Love your site…definitely one of the best and of great help to me in doing my 2005 chevy extended van conversion here on Vancouver Island. I’m just finishing the building of the actual hi-top now and then will be facing the electrical side of the project. The most daunting. I have a question though. I am interested in using your wiring plan system but there are a number of changes I would like to make in equipment, to suit my small budget. Does the planning set up your wiring diagram allow for changes in equipment rather than some of the choices given? Can I somehow swap one for another and have the wiring diagram produced show these changes? I look forward to your response. All the best you two. Enjoy life to the full and thanks for your help.

    • The diagram actually is “static”; it doesn’t update according to your choices. Sure it would be nice, but it’s way above our coding skills!! You can still change some of the equipment and use the diagram as a baseline; the concept would be the same.

      Hope that helps!

      • Antonie,

        First off, amazing site. It is streamlining my build a ton.

        So I did catch on that the wiring diagram was for YOUR build, and not updated based on the calculator that I did. Regardless, the wiring diagram is a huge help. Where I am getting somewhat stumped now is sizing the breaker, bus bar, fuse block, etc. I do notice that the “Items List” does change as I change selections on the calculator. Is it safe to say, if the calculator is done properly, the “Items List” is updated based on what I input on the calculator?

        Thanks much!!

  12. I chose a Lithium set up, but I see the Samlex SEC-1280UL 12V doesn’t mention it working automatically with Lithium batteries. Does it support Lithium?

    • Because they need the same charging voltage, Lithium batteries can be charged with the “AGM” settings of any smart charger (like the Samlex):
      “There are some chargers and controllers that are programmable to get full usage out of your battery, but most will have an AGM setting which normally bulk charges about 14.4 volts and floats at 13.6 volts. These levels are great for your Battle Born battery.”


  13. Thanks for the help. Just wanted to let you know the B2B is wire wrong according to the sterling manual. The negatives aren’t hooked up right. The manual also recommends larger fuses than those shown. Just a heads up. Great site!

    • Hi Jason,
      Negatives are as per manual, take a second look. That’s how our own B2B is installed and we confirm it works!
      Fuse are sized per manual V51 (70A); they changed the fuse size recently (100A) for some reason (V68). Can confirm the 70A works!

      Have a good one 🙂

  14. Super helpful. Thank you.

    A recommendation: The download for the wiring diagrams says “download YOUR wiring diagram and tutorial.” It should say “download OUR wiring diagram and tutorial.” After working through the thorough step-by-step calculator that you’ve created, I excepted this wiring diagram to represent the selections that I made for the system that I want to create. Instead, I paid $30 for a diagram that is a representation of the system that you created for your own van. The diagram of your system is available for reference (at no charge) on the first page of your Electrical Systems Design. Although I appreciate the time and energy that you put into gathering all of this information, I’m a bit frustrated that I purchased a product that was different that what you claimed it would be.

    • We agree with you. We replaced “YOUR” with “OUR” and added this note near the download button:
      “*At the moment, the wiring diagram represent the electrical system as we built it for our van. Our goal is to make it so it represent the electrical system as YOU designed it using this calculator, but we have a few technological challenges to overcome to make it happen… Meanwhile, our wiring diagram can be used to build any variation given by this calculator! :)”

      How does this sound?

  15. Very nice feature but it doesn’t quite cover what I am considering. I’m currently looking at an all-electric system, no propane with 240V appliances, 600Ah Lithium battery bank, 3000W inverter, and a Nations Starter and Alternator 280A dual alternator kit for charging the Lithium batteries.

  16. Congrats guys, this is very cool!

    Would you mind me asking how you do your web design? Are you writing in Python or some other language?

      • Amazing resource! I’m planning on doing the alternator connected to a battery to battery charger connected to a 200ah Renogy 12v battery. I have a 2006 dodge sprinter with a 150A alternator output. I’m having a hard time finding any resources that tell me the sprinter’s amperage to get the Amps available on the alternator. I used your calculator and tried various options (60A-90A) and received a “up to 40A battery charger”. I see that Renogy only makes a 20A and 40A. Is there a difference or recommended battery charger? If it says up to 40A, would 40A be too much? Is 20A the best option? Also, does your diagram show how to connect the battery to battery charger to the alternator? A person was helping me convert my van but ending up being a scam artist and now I’m left with partial wiring. Trying to figure this out on my own! Any help would be appreciated!

        • Hi Alyse,
          A 200A AGM battery should be charged at a rate of around 20% its capacity, hence 200 x 0.2 = 40A.

          Therefore, a 40A Renogy B2B is your best option.

          The Renogy owner’s manual will describe how to hook it to your van, and you can go on the Sprinter forum to get help from others fellow Sprinter owners: (we personally converted a Transit, not sure about the Sprinter…).

          Hope that helps!
          Good luck,

  17. Hi there –

    First of all, I can’t tell you how incredibly helpful your site is. To the point, I’m having trouble wrapping my head around the difference between 12V and 120V. Additionally, what things actually run on 120V vs 12V. Looking at you 120V list it’s much smaller, but in my mind, all of those things plug into a standard 12V outlet, right? Anyway, I’m starting to fill out your extremely handy calculator and want to make sure I’m taking everything into account so any additional information would be great. Thanks again!


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