Sizing Methodology
We Don't Design for the Average.
We Design for the Worst Case.
Most solar failures happen in December, not July. Here is the exact 4-step methodology we use to guarantee 99.99% reliability for critical industrial loads.
The "Average" Trap
If you Google "Sun Hours in Texas," you might see an average of 5.5 hours. If you size a system based on that number, it will work great in July.
Unlike residential systems which can lean on the grid when the sun isn't shining, an off-grid industrial site has no backup. That is why we ignore the "Annual Average" and focus entirely on the Winter Solstice.
The 4 Pillars of Industrial Sizing
Winter Insolation Design
We calculate solar array size based on December 21st (Winter Solstice) sun hours. This ensures your batteries can fully recharge even on the shortest, darkest day of the year.
Days of Autonomy
Batteries are sized to run the load for 5 to 7 days with zero sunlight. This "No-Sun" buffer is critical for surviving winter storms or extended cloud cover.
Array-to-Load Ratio (ALR)
We size the solar array to produce 120-140% of the daily load in winter. This excess power is required to refill the battery bank after a storm passes.
IEEE 1013 Compliance
We follow IEEE Standard 1013 for sizing lead-acid and nickel-cadmium batteries for PV systems, applying rigorous derating factors for temperature, dust, and aging.
The Engineering Formula
This is the simplified logic our sizing calculators use to ensure your system stays online.
Daily_Load_Ah = (Watts / Voltage) * 24_Hours // 2. Size Battery (with safety margins)
Battery_Bank_Ah = (Daily_Load_Ah * Autonomy_Days) / Max_Depth_of_Discharge // 3. Size Solar Array (for Winter)
Min_Array_Watts = (Daily_Load_Wh * 1.3_Safety) / Winter_Sun_Hours
* We also apply coefficients for temperature derating (cold batteries have less capacity) and system efficiency losses.
Ready to spec your system?
Use our interactive Industrial Sizer to get a preliminary spec sheet based on these exact standards.
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