Sizing a System
'Sizing' a system means determining how much energy is required and how many solar modules are needed to generate it.
A solar power system must provide enough energy to replace what is being consumed daily by the loads; lights, appliances, equipment, etc. Plus some additional output to compensate for energy used by the system itself.
To do your
system sizing, here are the two main things you will need to know:
- How much electricity will you be using
You calculate this for every load and then add the results together. Electrical use is figured in terms of 'Watt-hours'. This is the appliance's power rating (Watts) multiplied by the average amount of time (hours) it operates daily.
In addition to the electricity used by appliances, the system itself also consumes some power. For example: you do not get back all the energy you put into a battery; an inverter uses some energy to convert electricity from DC to AC; and voltage is lost as electricity travels through wires. A factor to allow for these needs is included in our online worksheet.
- How much electricity will be produced by a solar module ?
You estimate this by multiplying a module's power rating (Watts) by the 'Area Factor' from the map included in our online worksheet.
This gives you the typical Watt-hours produced per day by a solar module at an average location in the area.
Please keep in mind that every solar installation is unique and is affected by many factors, such as:
- Local weather patterns:
These can vary greatly even within a small geographic area.
- Installation:
Even brief shadowing effects a module's daily output and modules that are not oriented properly toward the sun will produce less power.
- Seasonal changes:
This estimate is based on a yearly average. The energy produced in winter will be less than average and in summer it will be more than average.
The number of modules needed will vary based on these factors. You may also desire back-up battery capacity and may want to anticipate future needs by having additional solar power now.
Click here to continue to the online system sizing worksheet.
