If you’re reading this right now, there’s a really good chance you’re doing it on your phone or computer.
Both of which you probably charged up from a wall outlet without thinking about it.
For tiny dwellers and those interested in alternative lifestyles though, it isn’t so easy.
Thankfully there’s a solution.
Solar power systems have improved massively over the last decade or so. They’ve finally reached a point where they can provide all the power needed for a comfortable off-grid lifestyle.
Today we’ll cover the basics of sizing your solar system, the major components, and give you a primer on putting the whole thing together.
Taking the First Steps to Solar Self-Sufficiency
When you’re planning a tiny home solar power system, you should start by writing down exactly what you need to power. Include things like:
- Game Consoles
- A/C Units
Once you know everything that will draw power, you can calculate how much solar you’ll need.
It’s always a good idea to add a little wiggle room to this total in case you need extra power for anything.
This allows you to size both your solar panels and your battery bank.
Next, you need to decide if you want to DIY your tiny house solar system or go with a commercial solar setup.
Ready Made Solar Systems
If you’re looking for something more plug and play, there are several options available to you.
By far the best is going to be from a company, known as Goal Zero.
They make totally self-contained solar power generators that combine a charge controller, battery, and inverter into one easy-to-use device.
This allows you to hook them up directly to either Goal Zero portable solar panels or to your own.
The Goal Zero Yeti 1250 is a complete solar power generator that provides you with a ready to use system right from the get go.
It’s designed to hook directly to any of Goal Zero’s solar panels, but can also be connected to standard panels through an adapter.
It’s capable of accepting up to 240W of power from solar panels.
The basic system includes a 100Ah AGM battery.
It’s rated to provide power for up to 10 devices at a time and is capable of powering a standard fridge for 20+ hours without additional charge.
This gives it significant capability on it’s own, but what really makes it special is its chaining function.
You can connect the Yeti 1250 to other 12v batteries to be charged as well.
This means you can have up to several hundred Ah of power on hand at a time.
The Yeti 1250 is a great system if you have very limited power demands and don’t want to go through the trouble of fully wiring your tiny home.
It allows you lots of flexibility while still giving your excellent utility.
The Basics of a DIY Solar System
Off grid solar systems seem intimidating at first, but are actually quite simple once you break them down.
Solar panels convert the photons of the sun into electricity.
That connects into a battery bank through a charge controller that then flows to an inverter and becomes usable household power.
There’s definitely more in the details, but the bones of the system are quite easy to figure out.
One big disclaimer before we go any further.
Working with electrical power always involves risks. If you aren’t 100% comfortable wiring your tiny home, it’s a very good idea to hire an electrician.
They have the specialized training and know how to properly hook together with your solar system and the rest of your tiny home’s electrical setup.
Even if you decide to build the system, you should probably have a licensed electrician look it over before turning everything on.
They may be able to spot something you missed that could have serious consequences.
Solar panels are the largest and usually most labor-intensive part of building your solar array.
You need to position them for maximum sun exposure and mount them properly.
If you’re installing them on a Tiny House On Wheels (or THOW), it’s imperative you make sure your attachments will stand up to the wind while driving.
When you’re comparing solar panels, you should look at two basic figures:
- Solar Cell Efficiency
A watt is a unit used to measure electricity.
The wattage of a solar panel tells you how much power a specific panel will produce under perfect sun conditions in an hour.
Most modern home panels will produce about 100 to 200 watts per panel.
Cell efficiency determines how effective a solar panel is at capturing the energy of the sun.
A panel with 20% efficiency would produce 100 watts of power per square meter.
Solar panels with higher cell efficiency produce more power for their size but are generally more expensive.
You also need to decide how you want to wire multiple solar panels together in your solar system. You can wire them together either in parallel or in series.
Wiring your solar panels in parallel requires you to connect all the positive terminals together and all the negative terminals together.
This has the effect of increasing the amps produced by the panels additively.
The benefit of parallel wiring is in it’s redundancy. If one panel or connector breaks down, the whole system won’t stop working, and power will continue to flow from the other panels without interruption.
If you’re using a PWM charge controller, this is how you’ll need to wire your panels.
Wiring in series requires you to connect the positive terminal of one solar panel to the negative of another, in series, until you’ve connected the whole solar bank into the charge controller.
This has the effect of increasing the voltage produced by the panels additively while leaving the amps the same.
A good way to think about wiring in series is old Christmas lights.
The power flows from panel to panel through the system the same way it would from bulb to bulb.
This has the same downside those old Christmas lights had as well: if one panel goes out, the whole system will stop functioning.
The benefit of wiring panels in series is that there’s less line loss.
For most tiny dwellers, this isn’t a big consideration, but if you’re building an off-grid homestead with your solar panels a good distance from your house, it is something to consider.
If you’re planning to use an MPPT charge controller, you should definitely wire your panels together in series.
A charge controller takes the power produced by the solar panels and regulates it to charge your batteries.
Batteries are actually pretty delicate, so it’s essential you have a high-quality charge controller in your system.
Charge controllers work by controlling the voltage and speed batteries charge.
They also prevent your batteries from overcharging and damaging themselves.
There are two main categories of solar charge controllers on the market today: Pulse Width Modulation (PWM) and Maximum Power Point Tracking.
They each rely on different principles to charge your batteries, but operate in a very similar manner.
PWM charge controllers were a major breakthrough once upon a time, but have now been overshadowed by MPPT charge controllers.
While PWM are adequate for small scale solar systems, they are not the most optimal choice.
MPPT charge controllers, on the other hand, are able to capture up to 30% more power from solar panels than PWM charge controllers.
One of the biggest downsides to Direct Current (DC) power is line loss from low voltage transmissions.
And while PWM charge controllers can only handle voltages of up to about 18v, MPPT charge controllers are able to handle significantly higher voltages and convert them into amps.
This has the effect of limiting line loss and capturing the extra power that would have been lost.
In summary, when it comes to the quality of charge controllers, it is without question: MPPT charge controllers are the best option. (Sorry PWM…)
Build Your Battery Bank
The solar panels are just one part of a solar powered tiny house.
In order to use the power your panels are generating, you need a way to store and regulate it. That’s where solar batteries come into play.
Sizing Your Battery Bank
When you’re sizing your battery bank, it’s very important you consider how much power you’ll need between charging cycles.
Most batteries will have a shorter useful lifespan as you increase their depth of discharge (DOD).
This is based on a percentage of their total battery capacity, measured in amp hours (Ah).
As you increase the depth of discharge, you lower the number of charge/discharge cycles the battery has before it fails.
A good rule of thumb is to take your power demand figure and double it.
That gives you about as much power as you’ll need on a regular basis, while still preserving the useful lifespan of the batteries.
Types of Batteries
There are tons of different battery types available, but for most tiny house and off grid needs, only lithium and lead acid batteries will work.
They hit the sweet spot of functionality and price that makes them perfect for our purposes.
Lead Acid (AGM)
Lead acid batteries have been in use for decades. Your car battery is a lead acid battery, as are most of the large batteries you’ll have encountered in your life. They work using lead plates suspended in a solution of sulfuric acid.
In the past, lead acid batteries required significant upkeep and care, but advances in absorbent glass mat (AGM) batteries have made them much easier to work with.
These are sealed batteries that require almost no maintenance compared to older generation lead acid batteries.
They still require venting for safety’s sake, but you won’t have to add distilled water to them.
Lithium Iron Phosphate (LFP)
LFP batteries have only recently become available for tiny home solar use.
They have a number of advantages over lead acid and other battery types but can be quite costly.
One of the best things about LFP batteries is their allowed depth of discharge. You can run a lithium-ion battery all the way down to 80% regularly.
This gives you significantly greater usable power than a similarly sized AGM battery.
They’re also lighter and allow far more cycles than AGM batteries.
Many come with up to a 10-year warranty compared to, at best, a 3 year warranty for AGM batteries.
They cost more upfront, but are much easier to work with and provide you with superior energy density.
If you can afford the initial costs, LFP batteries are always the way to go.
An inverter is designed to step up the DC power of your batteries to the standard AC power used by modern appliances. They come in two different varieties:
- Pure Sine Wave
- Modified or Quasi Sine Wave
Modified sine wave inverters are cheaper and less effective.
They’re okay for things like large appliances but aren’t great for delicate electronics.
If you want to charge your smartphone, laptop, or use your TV, you’re going to need a pure sine wave inverter.
Pure sine wave inverters are more expensive than modified sine wave inverters but much more effective.
They allow you to provide nearly the same quality of power from your DC batteries that you would receive from a standard home outlet.
Breakers, Fuses, and Disconnects
This one will be highly subjective to your design and how much additional protection you want to build in.
However, there are a few components that you should always use to protect your investment. These include:
- In-Line Fuses
- Low Voltage Disconnect (LVD)
- Disconnect Switches
In-line fuses should go between the solar panels and the charge controller, the charge controller and the batteries, and the batteries and the inverter.
These allow you to protect the different components of your system from a short or overload that takes out one part of the system.
The fuse you place in them will vary based on the size of your solar system and how much power each line is carrying.
The disconnect switches should go in the same places so you have the option to totally power down the system for maintenance.
Make sure you follow the proper shut down sequencing.
Start by disconnecting the solar panels from the charge controller, then the batteries from the inverter, and then the charge controller from the batteries.
The low voltage disconnect goes between the inverter and the batteries. It prevents the inverter from over-discharging the batteries if you go too long without sun.
All of these systems should be connected on the positive cable.
Putting it All Together
When you’re hooking the various parts of your solar system up, there’s a very specific order you should do it in.
You should also make sure that all the disconnect switches are turned to the “off” position as you’re connecting the system.
First things first, never connect your solar panels to your charge controller before connecting your charge controller to the battery bank.
The solar panels should be the last thing you hook into an otherwise complete system. If you hook the panels to the charge controller, first you can burn out the system or even cause it to explode in extreme cases.
Once you hook the batteries to the charge controller, it should turn on and cycle through some settings.
Follow your manufacturer’s instructions for set up and then connect the inverter to the batteries.
Only then should you connect the solar panels to the charge controller.
Sustainable Solar Living
With a properly set up tiny house solar system, you’re free to go anywhere you like without being dependent on the power grid.
This gives you the flexibility to live in the middle of a city or the middle of nowhere.
Now that you’ve got your tiny home solar system figured out, don’t forget to plan for your water and bathroom needs as well.