Solar technology is awesome, but it’s also awesomely confusing. Between batteries and panels and chargers and inverters and controllers and more, figuring out a working solar system is a daunting task, especially when space is at a premium. A few weeks back, the Matchbox got solar, and so—in the hopes it’ll help someone looking to unplug a small house of their own—here’s the full scoop on my working solar set-up.
To begin, this system was not cheap. Affordability was always a secondary concern for the Matchbox (trumped by reliability and livability), so at $8,400, these components may be out of the price range of some. It can be had for cheaper—indeed, I spent a little extra to order all the parts together, and a lot extra on a pre-wired FlexPower unit (which contains the charger, inverter, controller, and more), rather than risk death by electric trying to get those individual components wired together.
It also wasn’t easy. Even with a pre-wired unit, the installation was way complicated. I was fortunate to get a ton of help from a great and electrically-inclined friend, but getting everything hooked up took the two of us about four full days. For a novice, a professional installer may be necessary—and come at a higher price. (Despite the struggle, learning the ins and outs of the system was a ton of fun, so perhaps this would be a good week-long project for a persistent DIYer.)
Not cheap, not easy, but it does work. Well. Or at least, sort of. I’ve been running the system for a few weeks now and it does just great—even with my AC refrigerator and non-LED lighting, it drains less than 15% of the battery bank during an average day of use, and that’s without recharging. The thing is, the Matchbox currently rests under a pretty thick tree canopy, blocking all but the most indirect sun from touching the four panels on the roof. As such, it’s not really recharging—and won’t be able to until it moves to sunnier pastures—but once it can charge up, it should top the battery bank off fairly quickly.
So, those are the caveats. These are the details.
- The panels: 4 SolarWorld SunModule 315W/24V monocrystalline panels. Your basic 315W panels. The Matchbox roof (and most other roughly 8′ x 20′ flat or slightly pitched roofs) can fit four, for a total 1.3kW array.
- The batteries: 4 Trojan Reliant L16-AGM 6V 370AH sealed batteries ($499 each, $1,996 total). Safe for small interiors, compact, and capable of storing 1,480 amp-hours (roughly 9kWh). Note that these particular batteries are pending recall for a non-urgent sealing issue, so perhaps the Trojan Reliant’s aren’t, well, all that reliant.
- The unit: FlexPower ONE VFX3524 pre-wired system, including AC/DC boxes, inverter/charger, FLEXmax charge controller, and MATE3 hub ($4,035 total). Perhaps overkill for such a small home, but magic nonetheless. Capable of charging batteries from the sun, inverting DC to AC and AC to DC, charging batteries from a hook-up or generator, and keeping everything running and monitored and safe.
- The odds and ends: connector cables (2), connector key (1), combiner box (1), locknuts (2), breakers (2), rails (4), end-clamps (2) and mid-clamps (1), l-foots (2), battery connectors (3), and battery cables (1), all totaling $507. Another $520 for Massachusetts-to-DC shipping, and about $100 in tools (crimpers, wire strippers) and parts (wire, ring connectors) from the hardware store.
I got all this from the folks up at altE in Boxborough, MA, who were great in helping me figure out what I needed. They weren’t the cheapest, and this is in no way a paid referral, but feel free to use my sales order (SO-127929) as a starting point if it helps—or, y’know, comparing prices of the above links across the internet for the best deal.
So, those are the parts, but in such a small house, where do they go? Well the panels, obviously, go on the roof, and take up most of the seating space up there (though this amazingly entertaining strength-testing video suggests they’re more than sturdy enough to sit on). The FlexPower unit goes where the electric fireplace used to go, taking up about 33″ x 20″ of wall space and jutting out about 13″ from its mounting plate. The batteries sit on the floor underneath, occupying about four square feet in the corner. And the circuit breakers go in a back bumpout, though these could easily be installed right next to the FlexPower unit. Altogether, the interior solar bits and pieces take up about as much space as a small corner desk might (a really small corner desk).
It’s worth noting that the batteries and inverter/charger will give off heat, so best to keep them away from combustibles and be mindful of that heat during the warmer months. They’re also heavy. The main unit weighs 110 pounds, and each battery about 115, so assuming those are all tucked away in one corner of the house, that’s about 600 pounds shoved in one corner of a small, trailer-supported house. Considering another 200 pounds for the four panels (50 pounds each), a solar system of this size will add nearly 800 pounds to a tiny house—not an issue for those built on 14,000 GVWR trailers, but definitely a concern for a single-axle model.
And, finally, your
mileage wattage may vary. The Matchbox system is a good system for the Matchbox—or at least, it’s been doing okay so far—but solar is a big investment. Let me know if you have questions in the comments below, and I’ll let you know how the system does as we move into the hotter (and then colder) months, but whatever you do, get a second opinion before dropping thousands of dollars on a tiny house solar system.
More pictures to come, but for now here’s another look at the unit and batteries.