Solar for Tiny Houses
What energy sources will you use?
Deciding whether or not solar will be utilized as a power source in your Tiny Home (TH) is important. In the beginning, we considered it.
I have a background in solar energy so the decision was easy for us.
Understanding basic distinctions in the term solar is a good place to start.
The first, and most primitive, type of solar is passive solar. This is very simple and doesn’t require moving parts or sophisticated technology. It is often implemented in the design stage of building a home. Passive solar design utilizes climate, building materials and building site to minimize energy use. It takes advantage of the fact that placing objects in the sun will heat them up and placing them in the shade will cool them off. Efficient insulation and windows contribute to energy savings in a passive solar design.
One can build a home to utilize this type of solar energy by facing windows toward the south (in the northern hemisphere) to allow sunlight to warm the structure. Passive cooling can be accomplished by building under trees or adding shading to windows to block the sun’s radiation. Painting a house black will result in a warmer house than a white one assuming the sun shines directly on it, this is another use of passive solar.
Another basic kind of solar is solar thermal which involves heating water using the sun’s radiation. For instance, a hose or collector can be left out in the sun until the water inside of it heats up. Then the water is pumped to a faucet where warm water is achieved. Solar thermal technology is used to heat water for homes and pools. It is also simplistic.
A third, and most techy type of solar is Photovoltaic (PV). This means making electricity with the use of solar radiation and solar cells or panels. Electrons are freed when the sun directly hits the cells and a current is produced. A group of cells make up a module and a group of modules is called an array. Most people are referring to this when they think of solar, though all three types are loosely called “solar” because they use the sun for energy.
Generic solar info we have seen suggests that solar is the supreme way to power a TH.
I worked and taught in the solar industry for years and lived in a solar powered home for more than a decade. My Florida home combines solar thermal hot water with a PV array.
The costs and benefits of solar are much more complicated than what the general public realizes and though the idea seems like a no-brainer, it’s really not that simple.
For starters, Solar is not cheap. Since TH living is often inspired by keeping a keen eye of finances, this matters. It is a brilliant cutting-edge solution that is only used, for now, by those who are willing to pay the hefty up-front price. Owning a solar PV application on your TH will increase the cost, perhaps more than other energy solutions. It might not make sense. On permanent residences, there are incentives, rebates and refunds available to bring costs down, but they don't exist for Tiny Houses.
If you are only aiming to power a few small loads, a single panel may work, but if you are planning on heavier loads, you will probably need multiple panels to generate enough electricity to power your place.
It might make sense to design a hybrid system in which solar PV is combined with solar thermal (i.e. to heat your water) and perhaps gas could run certain appliances.
Batteries Not Included
Solar panels make electricity in real time, but they cannot store it.
If you intend on exclusively using solar, you will need batteries to store the electricity when the sun is not shining or at night time. Batteries are expensive and add more complexity to the system. Relying only on solar PV to power your TH will be a challenge unless you are comfortable with spotty electricity when the sun is not available due to rain, snow, clouds, night, shade, etc.
If you decide that the costs are worth it, there are still several other requirements that must be met for a solar array to make sense.
Is Grid Electricity an Option?
Where your TH will park comes into play here. If you will be buying land for a permanent residence, using grid electricity will possibly be more affordable, depending on your location.
If you plan to travel to RV or TH parks, they will likely have electrical hook-ups available like many campsites and you can plug in to their sources.
Energy usage in homes in the U.S. is measured in units called kilowatt hours (kWh). Utilities bill their customers based on whatever the current price per kWh is (1000 watts for 1 hour is 1kWh). This price includes the cost for the energy production (sometimes called fuel charges) and then there are usually fees and taxes tagged on. Most places in the continental U.S. pay anywhere from 8-22 cents per kWh. Alaska pays around 20 cents and Hawaii pays around 32 cents per kWh!
The national average right now is around 13 cents per kWh for residential use. If you pay 14 cents or more per kWh you are paying over the national average. If you pay less than that, congratulations, you get really cheap electricity! The more expensive your rate is, the more a solar array would make sense (assuming financial considerations are primary).
But, if you have cheap electricity rates in your area, you may not benefit from installing a solar array on your home because using your utility electricity is cheaper.
However, if you plan on being in the wilderness where no grid electric is available, solar PV may be a solution. Even then there are considerations.
How much sun will there be?
The more solar radiation an area has, the higher its solar potential. The sun shines more intensely in certain areas of the country and those areas have the potential make more PV electricity than places without as much sun. Check out this map to see how many “sun hours” per day your area gets on average. In areas with more sun hours, there are more kWh produced per day on average.
The American South West gets great sun, but the Pacific North West does not. Solar may work great for an Alaskan summer, but the winter may pose some real problems.
Beware of trees
Photovoltaic solar panels cannot be shaded.
Any trees, buildings or tall objects that are shading the panels will cause significant loss in electricity production. Since the sun’s radiation is generally strongest from 10 in the morning until 4 in the afternoon, it is critical that during these hours, your solar panels do not get any shade. Since the sun hits your home from different angles throughout the year, you have to make sure that you have year-round shade-free sunshine.
PV modules should face the sun's path to the greatest extent possible. In the U.S. this means south. They work off of direct sunlight, so if you were to mount them facing west, for example, they would work at their peak in the afternoon instead of from morning to dusk because that is when the sun's direct radiation would hit them.
The sun's path changes slightly with the seasons, so the best place to mount them is where they receive direct sunlight for as much of the year as possible.
Modules should also be tilted slightly and the tilt is usually pretty close to the latitude they are mounted at. If your TH is mobile and often moving from state to state, this is a consideration.
In the continental U.S. panels should face south. So, it is best if your roof has a southern sloped side to mount panels on. If your TH is on wheels, you can park it to acquire the best sunshine.
A TH does not typically have adequate roof space to install a large system. In order to cram as many panels as possible, a shed roof could make more sense. Gable rooves will not have as much space on any one side. If you only have a small bit of roof space, you will only be able to install a few panels. If you have land available, ground mounting may be an option. The more square footage you have for panels, the higher your electricity generation capacity.
What do you need?
Depending on your desired power loads, solar may or may not work for you.
Powering your TH with PV is doable, but you should know your limitations with it.
We were planning on living in our TH in the Pacific NW where electricity rates are relatively low compared to the rest of the country. Most of the grid electricity in Washington and Oregon is supplied from hydropower. Plus, we never intended to be in a wilderness area beyond the grid. I knew from experience the ins and out of Photovoltaics and for us, it did not make financial sense to install a solar array when we could get such cheap grid electricity by plugging in our TH to the local electricity company.
Additionally, our site is shaded by fir trees and located in northern Oregon where we don't get many sun hours. That is two more major strikes against its solar capacity.
We have a propane water heater and range. Our fridge, heater and lights run on grid electricity. Kelly built our TH with an extremely tight envelope. The windows are double paned and the insulation is thick. Our TH is very energy efficient, but solar was not part of our plan.
Have A Sunny Day,
This article contains excerpts from Can Solar Save You Money? A book I wrote for homeowners regarding their full-size houses (by Spike Andrews and sold on Amazon).
It was modified for Tiny House application.