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Thinking About Solar? Calculating Your Needs

Are you thinking about a solar charging system for your RV? Whether it is a large “run the air conditioner” type system or just some simple panels to keep the batteries charged on a long weekend, there are a few simple steps that will help your get started in finding the best system to fit your needs. There are a lot of factors that need to be calculated before you can even think about how many watts of solar to put on the roof. Continue reading my multi-part series on the DIY solar install I did to our unit in our transition to full-time RV living. (Also, we have a DIY Solar Facebook Page if you’d like to join – click here) We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to and affiliated sites. We would appreciate it if you find this information useful and are looking to purchase some of our recommended items that you would use our links provided, there is no additional cost to you.

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Your first thought needs to be what your realistic final outcome is going to be. What are you going to expect to be used and what are you going to use to provide the power for them? When we decided to move full-time into our RV, we agreed that there were certain luxuries that needed to still be available on a regular basis. One that Stacy requested was that she could still use her standard hair tools to include a blow dryer. We also really like our coffee in the morning. Now as you may or may not know both of those are pretty high draw items. We knew it was going to require a fairly good size inverter and battery bank.

Calculating Your Requirements

One of the first items that I think anyone who owns a trailer should get would be some kind of battery monitor that reads power through a battery shunt. When I installed my system I went with a Tri-metric 2030 battery meter. For this meter to work you will also need to get a Shunt and wire harness sold separately.

Tri-metric 2030 RV

It allows me to quickly see what my battery’s state of charge is and also to let me know what my current usage is. I would also recommend looking at the Victron battery meters. They come with a plug-and-play shunt and some models are Bluetooth capable right out of the box.

Victron BMV-712

Once you have the battery meter installed and temporarily calibrated to your current battery bank you will be able to check all your draws for the different electrical items in your unit. Make a list of each electrical item and how much they draw. You might notice that there are draws to your battery that are not switched anywhere in the unit. Most of those are your required detectors and alarms that are mounted that are never shut off. Those draws could be as high as 1.5Ah. But now you know they are there. That should account for any 12-volt accessories in the rig. Don’t forget to plug your phone into the USB jack if you have one to see how much that draws. Now take your list and calculate how many hours you will use each of those devices.

For 120volt loads, get a Kill-o-watt meter to plug the load into and turn on the load. The Microwave is more of a draw than the convection oven but since you have the meter you might as well count that as two separate components. Do you currently, or in the future, plan to use an induction cook plate? The coffee pot, toaster, and coffee grinder are some of the things we needed to include in our kitchen. Once you have the wattages for all of your items you will be able to figure out your minimum inverter size and your load numbers based on amperage draw.

Between the 12v and 120v load lists, you made calculate your average daily usage. Look at what the minimum size of a needed inverter if you plan to run your 120v items off your battery bank. A standard 2000 watt inverter should really have no less than a 400Ah battery bank. That will give you your additive baseline for sizing your battery bank. Check out part two of this series to help with battery bank and inverter decisions.

Recommended tools and materials required for installation

For drilling pass-through holes for cables and wiring, I would recommend a simple hole saw kit like this Vermont American kit utilized for deadbolt installations. The Victron battery meters also use a 2 1/8″ hole for mounting.

For running wire and cable through walls and along wire chases, I have found the use of fiberglass pull sticks like this Wire Noodler set to be extremely efficient and handy. I find that I use these for any kind of wiring from small to large projects. They will really cut down on the time and manpower needed.

9 thoughts on “Thinking About Solar? Calculating Your Needs”

    1. Hi Dave! We have a tad bit of a delay going on. We were invited to Wellington TX to be part of the cast and filming set construction for RV Nomads movie coming out in October. We’ll be getting the next blog done as soon as we can. Thanks for your patience! Glad you enjoyed it.

  1. Justin, I want to thank you for taking the time out of your busy schedule to help so many of us on the DYI Solar FB (Along with Rob Kenny and you other Solar brains) to not only size the system, but all of the components and wiring diagrams as well. WOW ! Yes, DYI anything can be a bitch-kitty to put together, but add AC and DC power into the equation and *BOOM* *SIZZLE* *ZAP*…Yeah, you know the drill. Thanks again Justin !

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