Building a Load Profile for Accurate Solar Sizing
Two homes with the same monthly bill can need very different solar systems — because one uses power at noon and the other at 8 pm.
Two ways in
- From bills: 12 months of kWh gives the annual total and the seasonal swing (aircon months). Divide by days for average daily kWh.
- From an appliance schedule: list each load’s wattage and hours of use by time of day. Slower, but it gives you the shape.
The daily shape
Sort load into buckets: overnight (11 pm–6 am), morning (6–9), midday (9 am–4 pm), evening (4–11 pm). The midday fraction is the share a grid-tied system can serve directly.
| Profile | Midday load share | Best fit |
|---|---|---|
| Work-from-home / retail / office | 50–70% | Grid-tied sizes up well |
| Family home, occupants out by day | 20–35% | Smaller grid-tied, or hybrid |
| Evening-heavy (aircon at night) | 15–25% | Hybrid with battery |
Seasonal variation
Design the array to the annual average but sanity-check the worst solar month against the highest load month — in the Philippines these often coincide poorly (cloudy wet season vs hot dry season), which is an argument for a slightly larger array or a battery.
Future load
Ask about planned EVs, additional aircon, or a growing business. A load profile is a snapshot; size with 10–20% headroom if growth is likely and the roof allows it.
EngEst Pro’s Solar PV Calculator accepts either monthly kWh or a full appliance schedule, builds the daily load shape, and uses it to size the array and battery and to estimate self-consumption in the financial model.
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