INTRODUCTION

There are actually three main alternative sources for electricity: 1) The Sun, 2) The wind 3) Running water. Of course there are others but these are the ones you will most commonly find solutions for on auction sites such as eBay. This guide shows what you have to look for when making your buying decisions.

MORE VOLTS IS BETTER

The first and most important thing to remember is that the lower the voltage of the system you buy, the thicker wires you'll be needing for it. The reason for this is based on a very simple piece of math called Ohm's law which states that voltage equals current times resistance. Therefore if you have a regular mains wire at 120 volts and capable of handling 60 amps of current – if you then choose to run a 12 volt power source through this wire you will only be able to carry 6 amps. To get the same amount of electricity through a wire at 12 volts you would have to have a wire capable of supporting 600 amps. Because of Ohm's law if you decrease the voltage 10 times you must multiply the current 10 times to get the same electrical throughput.

Even if you skipped through that little explanation, the results of it are simple, you really should try to buy the highest voltage system you can. If you can get 24 volt panels instead of 12 volt you will half the size of wire required – or if you can get a 48 wind turbine, the wire you will need will only be 1/4 the size it would have to be for 12 volts. This will save you a lot of money on wire.

The only downside is this. Lower voltage panels and equipment are generally cheaper as they were designed to run on standard car batteries. The higher voltage equipment you buy, the less you will find and the more it will cost. Therefore, when looking at what is available you should weigh up the different costs of equipment and wiring. This means get a good estimate for how much wire you will be needing first and find out the prices you can buy it for.

BATTERIES OR GRID TIED OR BOTH?

If you are not connected to the power grid you have only one choice – you must buy batteries to store the power you generate so you have it available for when the sun is out or at night or when there's no wind etc. The best batteries to buy economically are golf cart batteries. They are designed to allow many deep discharges and recharges. Regular car batteries simply will not do – the lead in them will be used up and the batteries killed in no time at all. Even marine batteries are still not as good as golf cart batteries (although they are a lot better than car batteries). Most golf cart batteries are 6 volts so you will have to create strings of them in series to make up the voltage of your system.

Alternately, if you have grid power you can actually use the grid as your battery. When your alternate power source is providing excess power you can sell it to the grid by spinning your meter backwards. However, this can cost several thousand dollars to get the right equipment as required by your power company. But then again, buying enough batteries to keep you going can cost about 2/3 of that – and you will have to replace them every 5-7 years or so. So make your choice. Some people have a smaller battery bank and also tie to the grid – this provides electricity to your house when there is a grid power outage. However, it is the most expensive of all three options.

Generally, even though it may cost more, unless you are experienced and confident with charging dozens of batteries safely (including the hydrogen gas released by them does not get ignited and is safely ventilated), and prepared to maintain the electrolyte and distilled water levels, it would be recommended to go for the grid tie system if you can – it will be plug-in and forget.

WHAT ELSE IS NEEDED?

So, when you have made your decision, if you are going the battery route you need to search for deep cycle batteries and power inverters that will invert from your system voltage up to 120 volts. If you are doing this yourself you will have some idea of ​​the power consumption of your house. If it is about 3Kw then you need a 3Kw inverter with 6Kw peak (to handle high short loads such as motors inridges starting etc). Many companies make inverters.

There are two main types: True sine wave inverters and modified square wave. Sine wave are the best and the most expensive – but they are as good or better than the power supply, so all your equipment will run smoothly. Modified square wave inverters are a lot cheaper but can make some hifis or TVs crackle. They can also make some electric motors such as fan motors hum. If this annoys you, you can get suppressor devices for many household items – or you may have to replace some of your items for ones that handle noisy power supplies better. The saving you will make getting a cheaper modified square wave inverter could more than fund replacing some of your less tolerant appliances.

If you are going for grid tie then simply look for grid tie systems. They will be true sine wave to ensure you give the grid as good a supply as it already carries.

SOLAR, WIND OR HYDRO

If you have south facing rooftops and at least 5 hours of sunshine per day, solar should work well for you. Alternately you can buy mounts that attach to a pole and track the sun for you, in which case only your average daily sunshine will be important. If you have wind above the national average then wind turbines are also something to consider. Beware though, some can be quite noisy. Also, for best results you need to mount them high up and may need planning permission etc. If you are lucky enough to have a stream or river running through your land you may well be able (subject to any planning requirements or restrictions) to install the easiest power generation equipment of all. A hydroelectric turbine is very easy to install, requires minimal maintenance, is less subject to high wind problems and can generate a lot of power, depending on the water flow.

GET A PROFESSIONAL TO INSTALL

Having read all the above you should have a basic idea of ​​what you can do to save on your electricity. But you really must consult a qualified electrician skilled in low voltage work. They will save you a fortune on mistakes you will likely make – plus they may well save you from electrocuting yourself. In conjunction with your electrician you should be able to draw up the specifications for an economic system that will pay for itself within 5 years.