Solar System Sizing & Setup

I"m sure this has been covered in the past but please forgive me as I am still a little lost.

I am trying to figure out what all I need (equipment wise) for my shuttle bus conversion… I want to be able to run a refrigerator, LED lights, small kitchen appliances, small vanlife type washing machine, etc.

I see a 40amp solar charge controller that is much cheaper than the same brand 30amp charge controller; if I’m shooting for a 30 amp system, would this 40a controller not be compatible?

I’m also open to hearing about people’s entire system (i.e. electrical system + equipment) details.

I will undoubtedly have more questions moving forward but just wanted to get this one out there to start with.
I really appreciate any help, I’m pretty uneducated when it comes to electricity.


Awesome, I’m doing a Shuttle Bus conversion as well! Just wanted to stop in and say hi, maybe poke ya about possibly starting a “Build Diary” post so we can see your progress and stuff as you go?

As for electrical, sorry but I’m too inexperienced to offer any suggestions there. Like you I’m also in the process of learning, but one useful tip I’ve picked up from just hanging around this forum and a few others, is that a lot of people seem to suggest using something in conjunction with solar.

Like using the Vehicle Engine to help charge the battery bank,or having a generator that can also do the same. Just something that works in unison with the solar so that it isn’t carrying the entire load on its own.

But like I said, I have zero hands on time, so take that with a grain of salt. My contractor buddy is still working out my requests for my electrical system, so I haven’t even reached “installing” status yet.

Best of luck, look forward to seeing your progress and maybe swiping some of your ideas for my Shuttle Bus! :smiley:


There’s 2 different schools of thought for solar panel systems…

A) Figure out your power needs and go from there.

B) Figure out how much roof space, or budget you have for solar, then work backwards from there.

Option B seems to be the simplest and most efficient to me.

Either way, most people are in for a very rude awakening. You need to remember that it’s not as easy as just having enough battery power to handle your desires. You also need a way to replace about 1.5x the power used, back into those batteries. Heating, cooking, refrigeration, and most forms of cooling are best performed with fuel powered equipment that does not require any electrical power.

That doesn’t mean we need to go without, just that we need to do it differently. The RV, marine, and off grid suppliers are great places for inspiration.

I like being prepared, so I have two separate, but interconnected systems. Each will power my van for about a week. When I’m driving, or charging by other systems, the two systems are connected, so both get charged. If not being charged, they are isolated from each other. Both systems are capable of powering my van for either driving or camping. While this doesn’t have anything directly to with solar, the time to consider this stuff is in the design stages before you begin actually building your system.

Many of us feel like solar should be an optional last step… Regardless, solar is just a very expensive battery charger, and the design of your electrical system is what needs the most careful attention, not the solar. What is going to supply your power system, batteries, generator, shore power, or some combination of them. I didn’t include solar here because it only a battery charger, and not a viable source of actually usable power. Any cloud can literally kill anything you have directly hooked up to solar, all your usable power must come from batteries, a generator, or shore power.

Most of us use both a generator or shore power mainly as a battery charger as well. The batteries act as a regulator, to make the power more stable. In cars, the battery supplies the cars power, while the alternator keeps the battery charged, for the very same reason.

The next thing to consider is whether we want a DC only system (the most efficient), or an AC/DC system, and exactly how we’re going to accomplish it. DC alone is pretty straight forward and easy. For AC we have multiple options to consider and explore. Do we want an inverter(s), or do we only want AC when using a genny or shore power, or do we want both, and how are we going to accomplish it.

Notice I said inverter(s) with an “s”. The most efficient use of inverters is to size the inverter according to your load. Oversized inverters can waste a lot of power, so multiple smaller inverters are a better choice, and all inverters should be turned off when not in use.

Now we need to decide where we want our outlets, which type where, and where do we want our switches, fuses, and circuit breakers. This should be given some very serious consideration, because future changes could be very difficult. It’s better to get it right the first time and plan for any possible future expansions.

I’ll call it good for this post, feel free to ask for anything additional, or even challenge me if you think I got something wrong.


"Never drive faster than your guardian angel can fly." ~ Unknown

WOW! Thanks for ALL that information. Really! I have a much clearer understanding now. I have employed the help of an electrician to guide me through the process but some of your info will undoubtedly supplement his knowledge for efficiency reasons.
I do happen to have some extra solar panels laying around so going with a solar charger is a simple decision for me along with vehicle/generator and shore charging options.

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in regards to the 40amp charger, I could be wrong but usually items like this are rated for their max. So it is capable of a max of 40amps. I do know the controllers have different efficiency rates based on their types. The Renogy site has a calculator where you can add equipment in and it basically spits out what you need to run your gear. Might be worth a shot , at least see if your ambitions as far as powering devices are possible. Good thing about electrical systems is they are usually pretty simple to modify once you understand them.

Hey there Rydel, for sure man, you inspired me to create a build thread. I think I’ve actually convinced myself (with the help of Van_Dweller ) to forgo the solar option and just have engine and port charging (from a campground or generator) By all means feel free to steal/improve on anything you see come abouts in the thread. I made quite a bit of progress yesterday but probably need to get my wiring figured out before going too much further.
Bed frame welded up and sheeted with plywood and got the outter shell of our sink/counter/oven cabinet.

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Don’t forget about mattress ventilation. Without it, moisture, mold, & mildew can build up between your mattress and the plywood. Common remedies are lots of 3" holes in the plywood, or a special type of pad/rug that goes between your mattress and the wood.

You can google “mattress ventilation”.


"If you prepare for the worst, every thing else is easier." ~ Off Grid

Alright, that’s all the rest convincing I needed to go with an expanded sheet metal with tighter mesh over that for the sheeting. Will also allow me to hang things from it in the “garage” under the bed.