Understanding Solar for Tiny Homes

At Wind River Tiny Homes we believe that when you receive your tiny home your journey hasn’t ended, it has only just begun. Having an overall site plan for your tiny house is important for making sure you get situated correctly. The site plans become even more important when your utilities are off-grid.

Going off-grid is no small feat. Planning is critical and the process of planning will help you get mentally prepared for what’s going to change – you are going to become your own utility company. It’s not easy, and it’s absolutely a meaningful challenge. When everything is set up and online you’ll have a very unique and valuable property.

Nevertheless, do not skip the reality check. When you are at home and the power goes out during a storm, somewhere there is a utility truck out in the rain addressing the issue. Where you’ve relied on the utility company in the past, now you have to rely on yourself. It becomes imperative that you understand your system, how to troubleshoot it, fix it, and to have a backup plan. This article is meant to be a first step in understanding photovoltaic systems (described here as solar power systems) as they pertain to tiny homes on wheels.

It's more than just panels

One common misconception we encounter is related to the components needed to go off-grid. Sometimes this comes from observing homes that have solar panels but are still grid tied. These setups allow people to sell energy back to the utility company when they are producing more than they are using. When the sun isn’t out and there is no solar power production, the grid power is used to fill in the gap. The components needed are essentially the panels, inverter, and various ancillary components. Grid-tied systems can also have battery backups, but you are still not off-grid per se. In addition to panels and the inverter, going off-grid requires batteries, charge controller, surge protectors, a battery monitor, and other ancillary components.

The batteries are a big one. In fact the primary challenge in going off-grid with solar power is not how to produce energy but how to store it. This is the broader problem for the energy economy as well for two reasons – cost and efficiency. For tiny home dwellers it’s also an issue of space. Out of all the options available, lithium batteries currently take up the least amount of space, and are more efficient, however they are significantly more expensive. Because space inside a tiny home is precious, our first recommendation to people is for them to consider making their solar power investment in their land and not their tiny house.

Solar panels can be mounted to the ground. The various components, like the inverter and battery can be wall-mounted inside a storage shed which you might need regardless because you will likely have a generator backup as well to make sure you do not run out of power in the winter months or heat in the summer months, depending on where you live.

Batteries

Many types of batteries are designed to never use their full charge. Different classes of batteries have different depth of discharge (DoD) thresholds which is the percent of charge drawn down from overall capacity. Some battery types, like lead-acid discharged by more than 50% DoD on a regular basis will affect long-term performance. Same goes for Absorbent Glass Mat (AGM) batteries. They should not be discharged more than 50% (some say 70%). This means that when shopping for batteries you have to add a factor to the battery for its DoD. Lithium-ion batteries have a higher DoD, but again they are more expensive.

When it gets down to it, lithium-ion batteries have a lot of advantages – they are smaller, have deeper DoD, do not off-gas, and, here’s the kicker, they are probably better for the environment too. There is a lot of emerging technology for using different materials within lithium-ion batteries to make them efficient, charge faster, and overall to make them more sustainable, so lithium-ion seems to be the way to go for the foreseeable future. Work lithium-ion batteries into your budget if you can.

Should you mount this system inside your tiny home?

Solar panels on your roof need to be pointed in the right direction. This limits your choice of roofline and the direction your home is facing. Technically the angle of the solar panels is supposed to be equal to the latitude of your location, however, changes in the angle have proven to only affect approximately 10% of production. The primary consideration is the direction your panels are facing. In most situations optimal performance occurs when solar panels face south at a tilt of about 30 degrees. If you have solar panels mounted to your roof, your site plan comes into focus to make sure the direction of your viewing windows, entranceway, and roofline all work in concert together. This is the reason we recommend ground-mounting the solar panels.

All those components we listed earlier, they take up a lot of space. We’ve installed the indoor solar system components in spaces measuring about 48″w x 24″h x 24″d but it was really tight. And that space may or may not include your batteries depending on what kind you get. That is precious space inside a tiny home. It could mean the difference between essential storage space or room for your solar components. Components also make white noise and require access for maintenance. Again, considering an outbuilding for your solar components is best and would allow you to have space for a backup generator as well. Consider your year-round climate. Northern states with winters where the sun never gets far off the horizon might be better suited to large battery arrays, backup generators, and ground-mounted solar panels that can be adjusted to follow the sun and to easily brush the snow off.

Wind River Tiny Homes can help

We recently did a case study with a tiny house situated in North Georgia. Over the course of the year, the 24 ft tiny home averaged just under 300 kilowatt hours (kWh) per month. The highest was 391 in February and the lowest was 207 in October. Every month the utility bill was less than $48. Pretty impressive energy usage and bodes well for a reasonably sized solar power system to make off-grid living possible. At Wind River Tiny Homes we can take your appliance schedule and create a detailed list that can be used as a starting point to size your solar power system. Some of our models come standard with a propane hot water heater which can also save on power. Options for propane cooking surfaces are available as well. Thinking about a propane fridge too, we’d advise against it. Their operation is overly complex, and the power draw of a 10 cu ft fridge is not going to break your budget when sizing your system.

Making the decision to invest in solar is a very personal decision, and one that we want our clients to be well informed on before investing in expensive and often high maintenance components. We hope this steers your research toward the best path for your unique situation!