Off the Grid in a Tiny House
The Cost and Practicality of Solar Power
Modern Tiny House
A Comparison of Energy Sources
Before anyone gets all excited about going off the grid and telling the traditional energy companies they are no longer needed, let’s look at a comparison of different energy sources.
Now, before doing that, let’s note that the desire to go off the grid with a renewable energy source like solar does not come down to just cost for many people. Some have ecological and environmental concerns. Others just like the idea of not being reliant on a company or agency which, not only will impose a cost, but also possibly rules or regulations. So for many, cost is not the only determining factor.
Unfortunately, solar, wind or other renewable sources of energy have become a religion to some, so one must take a jaundiced view of information on these sources. In fact, one can find information that actually states that wind and solar provide the same or less expense as conventional sources. This is patently untrue at the moment. However, a realistic view can be made up from rather clear information found from credible authorities. Also, figures can be skewed a bit due the relatively heavy subsidies that solar power might receive depending on the location.
Another recent factor to consider is the dramatic decrease in the cost of fossil fuels and the emergence of natural gas as a strong competitor to coal and other fuels for electricity generation.
Table showing costs as computed by the Department of Energy in 2014:
|Power Plant Type||Cost
(Solar PV stands for Solar Photovoltaic.)
As one can see, over a 100 hour period, the cost of solar amounts to $12.50 while coal spends $9.50 and up and natural gas $7.00 and up. (It should be noted that this article only applies to the United States. Other countries’ energy expenses are generally much greater than the US.) According to the National Renewable Energy Laboratory the average cost per watt for solar PV installation is $3.60.
Nevertheless, computing the expense of Solar PV is highly individual depending on location, local government and the type of system used. Showing all the various abstruse calculations does not clarify the purpose of this article. Leave it to say that solar is in general between 40 to 60 percent more expensive than the cheapest fossil fuel.
Types of Solar Setups Affecting Expense
The simplest solar PV setup contains a solar panel, a charge controller and a D.C. device or devices. In order to run A.C. devices, an inverter becomes necessary. A simple setup has limited application and delivers nothing at times of little or no sunshine. Storage batteries deliver electricity at night and during inclement weather. Batteries are by nature direct current devices, supplying usually 12 volts at various amperes depending on the size and cost of the battery. Generally a battery bank will set one back quite a few dollars, but is less expensive when purchased as part of a system.
For the purpose of this article, we will assume that the devices powered include a modest sized refrigerator, a television, a computer and attendant objects like a router, lights for a house around 300 sq. ft. and a small air conditioner with the occasional use of a washer/dryer. Appliances like the stove and heater can utilize propane. So we will need a system that can furnish a number of comforts and entertainments 24/7 during the night as well as during stormy, overcast days. If you are not located in a area like myself, the desert southwest, you would probably want a backup generator for those times when sunshine becomes hard to obtain.
Appliance Wattage List
|Refrigerator||1200 watt-hours /day|
|Television||Between 215 and 350 watts|
|Computer and Router||80-270 watts|
|Air Conditioner||1100-1600 watts|
|Lights||80 – 160 watts*|
|Miscellaneous||200 – 600 watts/day#|
*The lights are low voltage CFL bulbs.
#This would consist of things like a toaster or electric shaver.
Obviously, items such as the television or washer/dryer are not used continuously. The trick in computing the amount of electricity needed is to determine the watts consumed per day. If one washed clothes on a Saturday only, dividing the watts used by seven will give one the answer. The above example table shows the variability of computing an overall number.
Besides the load needed for a tiny house, location becomes a very important matter. Living in Palm Springs, California one would expect to collect significantly more solar power than someone living in Portland, Maine. Check out the Solar Energy Map at the Department of Energy which gives the watts per hour per feet squared per day.
The Solar System Size
For a system that includes the above appliances and electrical devices, the number of a kWh system will be somewhere between 86 to 232 kWh in a location with 5 peak hours for 30 days per month. This is for an off-grid system.
A lot of information is available on the Internet as well as calculators for the size of a system. A simple search for “solar size calculator” will give a tremendous number of results. Many companies include this as a resource on their websites.
Of all the sites that I have reviewed, the expense for a basic off the grid system starts at around $3500 for a very tiny house to up to $8000 for a small cottage sized dwelling in a location of sufficient sunshine. Depending on the factors, the cost can rise several thousand dollars. Now, this whole discussion only suggests solar for an off-grid system. A system can accept some power from other sources such as from the grid or from wind or gas generators. So a mixed system is less expensive. Nevertheless, individual needs as well as installation can lead to greater cost.
The life expectancy of solar panels figures into the equation. Most panels are warranted for 25 years with the expectation that they will produce at least 80 percent efficiency during this time. Other components such as inverters and charge controllers may not last as nearly as long. Batteries require regular replacement. For an interesting article on batteries for solar power systems click this link.
The reason this article is of such a general nature is because of the tremendous number of variables involved with solar energy production and differences in the various cost factors. The competition from solar energy companies leads to the most obvious notion of checking around for the best deals on a solar system. Ask any seller whether you qualify for a tax credit or subsidy or any other advantage.
The feeling of not being beholden to anyone for one’s power is tremendously alluring to many people. Not having to pay a monthly bill leads many to take the plunge and invest in a power source that gives them a greater feeling of freedom.