PlantmarginSizing solar from your own meters, not from a guess
Most solar quotes are sized from a monthly bill: kWh a month divided by a typical yield. That number says how much energy the plant uses. It says nothing about when it uses it, and for solar the "when" decides the value.
Why the hourly shape matters
Solar produces between about 06:30 and 18:30 near the equator, with a peak around noon. Every kWh produced when the plant is not using it is either exported (at a lower value), stored (at a cost) or curtailed (worth nothing).
Example: two plants each use 50,000 kWh a month.
| Plant A: two shifts, 06:00–22:00 | Plant B: 24 hours, heavy night load | |
|---|---|---|
| Daytime share of energy | about 70% | about 50% |
| Solar size before surplus appears at noon | larger | smaller |
| Best value without a battery | larger array | smaller array, or a battery |
The bill is identical; the right system is not.
What a metered profile gives the designer
- The real daytime load, hour by hour, on working days and weekends.
- The maximum demand, which limits the inverter size under net metering and drives the demand charge.
- Load that can move: pumping, refrigeration pull-down and batch processes that could shift into the solar hours.
- Weekend and shutdown patterns, when a large array would export or curtail most of its output.
How the size is chosen
A sound design tries many sizes, from small to the limit set by the roof, the demand or the net-metering cap, and costs each one over 25 years: equipment, installation, operation and maintenance, inverter and battery replacement, and module degradation. The recommended size is the one with the best net present value, and the alternatives are shown so the owner can see the trade-off.
Before the design
- Meter the incomer for at least two weeks, ideally a full month, at 15-minute or hourly resolution.
- Note shutdowns, seasonal peaks and planned expansions.
- Measure the roof or plot and note shading, structure and cable routes.
When Plantmargin already meters a plant, the solar designer reads this profile directly.