We installed a fairly large (for an RV) completely custom solar power system all by ourselves for right around $3000. It has 660 watts of panels, 540 amp hours (~6.5 KWh) of AGM batteries, and a 3000 watt pure sine wave inverter. This should be more than enough for us to have 2 people living and working remotely full time with about 2-3 days of reserve power if it gets cloudy. It wasn’t that hard, it just required a bit of research and a lot of time.
For starters if you’re confused about all the different components I was referring to above, I recommend a Gone With the Wynns piece on the basics of solar.
When we started looking at installing solar, I took a quick look at just paying someone to install it for us but I was amazed at how ridiculously expensive it was to have someone do it for us (a comparable system would have been over $7000 from an installer). Next we looked at DIY “kits”, but I was always disappointed either with the cost considering what you got or the poor quality of components and lack of safety equipment like fuses. I have a degree that says I’m an electrical engineer, so I figured I would be able to do a custom install, get all the quality I wanted for a reasonable price. I was able to make a system I’m pretty darn happy with for a not astronomical price. It was probably more than just running a generator for power for a year, but we hate generators. They smell, they are loud, they are un-neighborly and they are expensive to run.
Below is the basic diagram of how the major components in our system go together. There are a lot of details that are missing (primarily fuses and breakers, the current measuring shunt and the temperature sensors) but this is the gist of it. We ended up needing to be a little bit more complicated that most RV systems because the inverter/charger I found was a 24 volt unit instead of a 12 volt unit, but it was dirt cheap and perfect in every other way so it ended up being worth it.
And below is what it looks like installed. I still need to clean up some of the small sensing wires but the big ones are pretty at least. In the monitor it says that we are putting 00.7 Amps (~19W @ 27V) into the batteries from the solar panels.
Let’s talk about each of the components individually. (All prices are from late 2015 to early 2016)
This is the one area that people are right about when they say “Solar is getting cheaper all the time!” The panels themselves are indeed getting much cheaper. As little as a year ago when we first started investigating the whole RV plan, the metric for if you got a great deal was “do the panels cost less than $1.00 per watt.” And the only way you could pull it off was with giant industrial panels that we were never going to fit on our roof and then shipping was a whole other story. Small 12V panels we could use would be around $1.50-$2 per watt after shipping. Today is a different story though. You can buy them on Amazon for $1.30 per watt and I was able to find four smaller 165 watt panels (660 W total) that would fit on our roof for a total of $670 shipped to our door ($1.02 per watt). They are listing on their site for a little higher but I just called them up and said “I’m getting quotes, what’s the best you can do for four of those panels shipped to Denver?” and they came back with a great price. – $670
Solar Charge Controller
We bought a Bogart Engineering SC-2030 on the recommendation of Handy Bob Solar. Handy Bob writing is very “passionate” and can be very hard to follow, but he knows his stuff about solar on RVs. I’ll be sure to make our own review of the unit after we get some more use out of it. It also needed a temperature gauge for the batteries – $130 + $12.50 = $142.50
Granted you’ll want batteries even if you do just use a generator, but with solar they are a requirement. I got ours from craigslist for a song after some negotiation. I got four brand new 135 amp hour 12V AGM lead-acid batteries for $100 each. They retail for $330+ each so it was a fantastic deal. We thought about lithium batteries which compared to lead-acid batteries are lighter and smaller per amp hour, don’t have odd charging profiles so they charge much faster, can be discharged further without causing permanent damage and don’t release explosive gas if you screw up charging them (I only messed that up once); all of which would be good features in an RV. The problem is cost. If you want to go for lithium batteries like the Wynns or Technomadia, a similar amount of usable storage would cost close to $3000 at least plus shipping. I’ll keep the lead acid batteries for a while, thank you very much – $400
Inverters take the DC power stored in the batteries and convert it into AC power for your standard house outlets. You can also get integrated inverter/chargers that combine the inverter with the battery charger you’d use to charge your batteries from a hookup or generator. This is usually going to be one of the most expensive components in your system, especially because you often get what you pay for in terms of quality and longevity. You can save money by getting a “modified sine wave” inverter but those generally don’t play nice with electronics like our laptops so it wasn’t an option for us. You can also save money by getting one with a lower peak output but you’ll need to base it off of your expected usage. For us, we wanted to be able to run a microwave or hair dryer plus our laptops plus a fridge and maybe even the AC for a short time, so we went for a huge 3000W inverter but if you don’t use those things in your rig, a cheap 1000W inverter might be more your style. We also really wanted an inverter with Power Boost. Long story short, power boost (also known as “hybrid” type inverters from Magnum) allows you to run your backup generator way less often, have a smaller backup generator and be a good neighbor to friends who let you borrow an outlet by preventing you from tripping their circuit breakers. Usually big 3000W inverters with power boost are $1700–$2200 but I found one on Craigslist for $900. Big win there. It was a 24V system instead of a 12V system which made things a little more complicated, but I made it work. I also ended up needing a way to change the settings on it, and while they sell a monitoring and control panel, I ended up going with the computer interface which I got used for $70. – $970
Battery Monitoring Kit
Our battery monitoring kit is a Bogart Engineering Trimetric TM-2030 that pairs with the charge controller. This measures every watt in and out of the batteries so you know exactly how charged your batteries are and how much power your charge controller can put back in. It uses a very large and very precise resistor called a shunt to measure current in and out. We got the shunt, TM-2030 and the charge controller as part of a package deal for $290 with the charge controller being $130 of that, so the rest was $160. We also got a wiring harness to hook it all together for another $21. $160 + $21 = $181
Total for the big stuff was about $2350. Now lets talk about all the rest of the little things
- Fuses, circuit breakers and shut off switches so we don’t die – fuses (2 x $36) and holder ($35) for the Inverter, fuses (2 x $8.50) and holder (2 x $15) for each string of panels, breaker for the charge controller input ($30) and charge controller output ($30), inverter shut off switch ($35) – $249
- Panel mounting hardware –I made my own mounts from angle aluminum and some machine screws from the hardware store. Some 3M VHB Tape and some self-drilling screws to hold them to the roof and then some Dicor sealant to make sure the roof didn’t leak where the screws made holes. I also needed screws for the battery terminals that I’ll throw in this category – about $90
- Copper wire and connectors – Thick and thin, long and short you need copper, lots and lots of copper. And unlike the silicon in solar panels, copper is getting much more expensive all the time. 10 gauge outdoor wire for the roof ($31), outdoor connectors (2 x $7), more outdoor connectors ($9), 6 gauge wire from the roof down to the controller ($35 at Home Depot), 6 gauge connectors ($9), 2/0 gauge wire for the batteries and inverter ($63), 2/0 gauge connectors ($25), heat shrink tubing ($35) – $221
- Tools – I either owned, begged, borrowed, or stole all of the tools I needed except for a cable crimper ($35). I also needed drills, pliers, screw drivers, soldering irons, clamps, socket wrenches, and bolt cutters. – $35
So $595 on all of the extra stuff. Total cost all-in came out to right around $3000.
If you have any questions about the part selections or how it’s wired or really any part of it, feel free to reach out in the comments or via email. The information for how to do solar yourself is all out there on the internet but it isn’t exactly easy to find so I want to try to help however I can.