Size and Power

The most common size Solar Systems commercially sold are around 1.5 or 3 kW.

If you don't know what size you want or need then its best to figure out the power consumption of the house as a basis.  You can then decide to go higher or lower, depending on whether you want to generate and excess to put back into the grid, break even or just save on your electricity bill. The power consumption can be figured out two ways:

• By Calculation or,
• By Measurement

Measurement is the easiest method but means you need to connect a metering device to the supply wires, which normally needs to be done by an electrician.  It's reasonable to make an investment in a power meter at this stage because you will make use of it once you have your solar array and system in place.  It may be possible to get an idea of daily consumption by reading your meter daily, at the same time each day for some days - maybe a week.  This will give you the consumption for each day, but will not tell you the times during that 24 hour period when the electricity is being used the most, or the least.  A power meter designed especially will give you lots of information and log the power usage data too.

Using calculation is tedious because you have to figure out the power consumption of every electrical device in the house. This can be done by reading the information from specification plates on appliances or from the appliance's specifications in the user manual. Some things don't have such specification, for example lights, but you can read it from the light bulb.

ASKO washing Machine Specification Plate

I shall publish a spreadsheet to help with calculation, I haven't yet figured a format I am happy with. I will also go deeper into power measurement.