Sizing a home solar system is a writing exercise before it is a maths exercise. The buyers who get the right size are the ones who wrote the honest load list. This guide walks through the steps in order.
Walk through the house and list everything that draws power, with honest running hours. Include the loads people forget: the water pump, the refrigerator's constant draw, standby devices, outdoor lighting, the washing machine's weekly pattern. Mark each item as daily, occasional or seasonal. This list — not the floor area, not the family's size — is the document the system is sized from.
Step two is the backup decision: which of these loads must run during an outage, and for how many hours of darkness? That answer sizes the battery. Step three sizes the array to refill the battery and carry the daytime loads together. Buyers who reverse the order — array first, questions later — usually buy twice.
Compare your list with the worked example on this site, the 5KW home system with battery backup, whose page totals its household load list and checks it against the configuration. Your list will differ; the method should not. If your total is far from your shortlisted configuration's capacity, believe the list, not the brochure, and resize before you ask for a final price.
Before ordering, confirm the minimum order quantity and lead time for your configuration, and ask which documents apply to the exact system you are quoted.
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