EV Solar Products
2655 N. Highway 89
Chino Valley, AZ 86323
ph:928-636-2201   fax: 928-636-2015
e-mail: info@evsolar.com

Solar Electric System Sizing Guide


What do I need to run my home on solar power? This is usually the first question asked by those who are exploring the idea of using solar power to run their home. This page will help you to answer this question, and design a system that is suited to your individual power needs.

There are four questions you need to consider carefully and answer in order to create a good system design. How much energy is available? How much energy do you use? How efficiently are you using the available energy? and How much will it cost?

The first question addresses the availability and type of energy at your site: is it solar, wind, and/or back-up generator? The main source of energy we focus on is solar. To assess the amount of solar energy available to you, you must find the number of peak sunlight hours at your site. This information can be gathered from observation or from looking at tables and maps of peak sunlight hours in your area. These amounts vary seasonally, so you want to design your system to be able to work when you have the least amount of solar energy available.

For larger systems, or systems having particularly large loads, your back-up generator can also be made into a regular contributor. Because we are solar and renewable energy oriented, we like to minimize the use of fossil fuels as much as possible. However, in some cases, running a generator one or two hours a day can reduce the overall cost of the system, thereby providing a solution to the cost of a large solar system.

The second question you will need to address is the amount of energy that you use. In order to accurately size a system you need a fairly accurate idea of your average daily power consumption. It will take some time to estimate how many lights will be on and for how long, or how many hours a day the furnace blower will be on, especially if the house isn't built yet! However, this is critically important to the success of your system. You don't want to over-estimate, since this will artificially inflate the cost, and you don't want to under-estimate because this will create a system that is too small, leading to a greater chance of system failure, and shortening the life of your batteries. Therefore, it is important to spend the time to accurately assess what appliances and lights you use and for how long, and find the correct watt ratings for each appliance and light.

While assessing your power needs, you can answer the third main question: How efficiently do you use power? This is a good time to note what appliances and lights in the house use a large amount of power, and figure out if you want to replace them with more efficient products. Some items which provide considerable savings in energy are switching from incandescent lights to compact flourescent lights and switching to propane appliances. Some of the most common items to switch to propane are the dryer, stove, water heater and space heating. It is also a good idea to take a look at your refrigerator. It is often more cost effective to replace your refrigerator, especially if is it an older model, with a more energy efficient model. You also want to eliminate phantom loads by putting anything with a remote control on power strips so that you can completely turn off these units when not in use. Those appliances with a clock (such as microwaves, stoves and stereos) can also be put on a power strip.

If you are building (or even remodeling) a house, you may want to consider using passive solar design. By using some fairly simple design principles, you can create a house that stays warm in the winter and cool in the summer, helping to decrease the amount of energy needed to heat and cool your house.

All of these considerations lead to the last (and some say most important) question: how much will it cost? The more accurately you assess your energy needs, and the more energy efficient your appliances and home are, the more cost efficient your design will be.

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