Solar Electricity
Off-Grid Solar Array Calculator
Off-Grid Solar Array helps you find required array size from daily energy use, peak sun hours, and system efficiency. The page keeps the arithmetic visible so you can check the result against the original measurements.
Inputs for this calculation
Replace the examples with values from the same case.
Formula used on this page
For this worksheet, the governing relationship is array = daily energy ÷ (sun hours × system efficiency). The entered quantities are Daily energy use, Peak sun hours, and System efficiency.
Using the loaded examples gives 4.00 kW. Your saved case should identify where each entry came from.
Estimate off-grid array size from daily energy, sun hours, and system efficiency. If you also need daily solar energy, continue with Solar Daily Energy Calculator.
Measurements and entries
Base energy estimates on the limiting season rather than an annual average alone. Do not combine a worst-case value with unrelated nominal data.
A denominator entry cannot be zero. A prefix error can move the result by several orders of magnitude.
- Daily energy use
- Default example: 12 kWh. Enter daily energy use in kWh.
- Peak sun hours
- Default example: 4 h. Enter peak sun hours in h.
- System efficiency
- Default example: 75 %. Enter system efficiency in %.
What the number means
The primary answer, Required array size, describes only the entered scenario. Compare it with cold-voltage, hot-voltage, current, energy-yield, and controller limits.
A result without its source conditions is difficult to compare or audit.
Where this estimate can fail
Use the limiting-season solar resource and include site-specific shading and temperature losses.
The arithmetic intentionally leaves out seasonal resource variation and controller or inverter operating windows. Resolve material omissions before selecting a standard size or rating.
Use site-specific irradiance, temperature, shading, and equipment data.
Sensitivity check
Change Daily energy use from 12 kWh to 14.399999999999999 kWh without altering the remaining fields. The calculated value shifts from 4.00 kW to 4.80 kW.
The comparison demonstrates sensitivity, not a guaranteed field response.
Keep a reproducible record
Save daily energy use, peak sun hours, and system efficiency with required array size. Add the date and any unit conversion.
Transfer required array size without rounding when it becomes another input. Do not round between dependent calculations.
Before relying on the answer
Can I select equipment from this number alone?
The calculator does not approve equipment or supply an unexplained margin. Compare against a monthly or seasonal production case.
How much precision should I keep?
Do not round between dependent calculations. Match the final display to the precision of the source data.
What happens when a denominator is zero?
A zero denominator is undefined, so the affected field has a positive minimum.
Should I use measured or nameplate values?
Use daily energy use, peak sun hours, and system efficiency from one operating condition. Base energy estimates on the limiting season rather than an annual average alone.
Which assumptions matter most here?
Use the limiting-season solar resource and include site-specific shading and temperature losses. A broader review should include weather variability, mismatch, clipping, soiling, degradation, and curtailment.