I live on a rural property, 12 acres, about 30 minutes drive from Toowoomba, a city of about 110,000 people. When I bought the land in 2011 it was a vacant block, no buildings, few trees, but it did have a nice spring fed creek. There is no sewage service or water supply, but there was electricity going past the property.

First thing I did before building the shed and moving in a house was inquire about connecting to the power grid. I had to pay about $250 to the local power authority for a quote on connection, which took a couple of months for them to process. They came up with a price of $12,000 to connect power to a pole just inside my boundary, I would still need to run the power to the house and shed, about 150 meters back from the road. There was also a 6 month waiting period before they would start work! The $12,000 was acceptable, the 6 month waiting period was not.

So I considered going off grid. $12,000 could buy the parts to build a basic off grid power system, and it means I could get power connected quicker than the grid power option. Going off grid also means no power bills, and a sense of responsibility, plus I like the idea of using renewable energy, non polluting, ever lasting. Energy literally falls from the sky, seams kind of dumb digging it out of the ground.

I took the plunge and bought the hardware. It was a basic system, just enough to get me going, and something I could upgrade later. I'm a single bloke, no kids, so my energy requirements are pretty basic. But I also wanted the essentials, lights, entertainment, internet, and I like to use power tools, including drop saws and welders, so needed a system that could run my workshop tools.

A typical off grid system has a source, usually solar and/or wind, a charge controller, a battery bank to store the energy, and a inverter to convert the battery power to normal AC house hold power. For more information about sizing a system, see my article Off Grid System Sizing.

Choosing a battery voltage.

First up, what battery voltage should I use. You can buy hardware for 12, 24 or 48 volt systems. A 12v system is OK for a caravan, camper, or a small off grid system, but you are limited on inverter power rating, due to the higher currents needed to achieve the same watts.

Watts = Volts X Amps.

So if I wanted to boil a kettle, the system needs to supply around 2000 watts. 2000 watts from 12v is 166 amps! That's a lot, and needs beefy cabling from the batteries. Also 12 volt inverters rated for much more than 2000 watts are rare and expensive.

At 24v the amps drops to 83, which is much easier to handle than 166 amps. Plus the cables from the battery bank can be half the size. 24 volt inverters are typically available up to 4000 watts.

At 48v the amps to power our kettle is about 42 amps. 48 volt inverters can handle over 7000 watts, which is enough to run the average house.

So a higher battery voltage means less current, and this means you can buy a higher rated inverter, and therefore power more appliances at once.

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