Before you go forward on any project, it is crucial to first understand what needs to be achieved. If your project scope is inaccurate, you may find yourself with a faulty system.

The best approach is to start with a simple scope for your project. You can always iron out the details later.

Some suitable project scopes include:

• Powering a simple shed’s light and alarm on an allotment.
  • Powering lighting and simple electrical devices in a workshop with no mains connection - such as a kettle, radio, and a few handheld power tools.
  • Powering a recreational vehicle’s lighting, television and refrigerator.
  • Back-up power for lighting, four laptop computers, and an office telephone system in the event of power failures.
• Charging electric bikes.
  • Powering an off-grid holiday home with complete electricity requirements.

Once the scope is identified, you can start working on some calculations to estimate your power requirements. Again, we’ll use a small off-grid system for a holiday home to compute the total electricity requirements.

Starting with a small, off-grid solar electric system is best for understanding the design, although the project can continue to grow as funds allow.

Once the scope of the project is identified, you should quantify the exact requirements of the system with the necessary estimates of power required.

A small two-bedroom cottage, serving as a typical holiday home, with a standard fuel cooker and boiler may cost around $7,200 (£4,500) when connected to the national utility grid; but a solar system may bring the costs down considerably.

Assuming that the holiday cottage is mainly used in summer, autumn and spring, with an occasional winter weekend, there is a need to power the lighting – both indoors and out – the kitchen refrigerator, and a small television or radio. For many modern consumers, extra electricity would also be consumed for charging mobile phones, MP3 players, and laptop computers.

With the total electricity requirement listed, the next step is to determine the amount of energy each appliance requires, along with its actual daily usage.

To save as much energy as possible, we would prefer to use low voltages such as 12V or 24V wherever we can. The benefits are:

1)    No energy efficiency is lost with the conversion of low DC voltage to mains AC voltage, using an inverter.

2)    No secondary inefficiency is caused by a transformer on devices plugged into the mains, to re-convert high AC to low DC voltage.

Many electrical appliances in homes use external transformers. But transformers on 12V or 24V are more efficient than those made for mains voltages. However, there are disadvantages to low-voltage configurations, too. They may not be suitable for every project because:

1)    Additional rewiring is required for the 12V or 24V configuration, which will increase the cost of implementation. The final cost can be much higher than the cost of an inverter and a bigger solar array.

2)    More power losses can occur through the cable that runs from your battery to your devices in low-voltage configurations.

Check your home wiring. If the existing wiring links to the