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Solar & Renewables Calculator

Comprehensive solar and renewable energy calculations including panel optimisation, battery sizing, and electrical analysis.

Solar Panel Tilt & Azimuth
Calculate optimal solar panel tilt and azimuth for maximum energy production.

Panel Specifications (optional)

Results
Enter values and click Calculate to see results

About the Solar & Renewables Calculator

This solar and renewables calculator helps size an off-grid or backup system — estimating the panels needed for a daily energy demand, the battery capacity to carry it, and the voltage drop in the cabling. It turns a rough energy budget into a workable specification.

Sizing panels to demand

Start from your daily energy use in watt-hours, then size the panels to generate that much given your location's peak sun hours — the equivalent hours of full-strength sun per day. Panel output needed ≈ daily energy ÷ (peak sun hours × system efficiency), because inverters, wiring, and dirty panels lose some energy along the way. The calculator builds in this efficiency so the array actually meets the load rather than falling short on dull days.

Battery capacity carries you through nights and cloudy spells. It is sized from the energy you must store, the days of autonomy you want, and how deeply the battery may be discharged — lead-acid likes shallow cycles, lithium tolerates deeper ones. Undersizing the battery is the usual cause of an off-grid system going dark.

Voltage drop in cabling

Long, thin cables at low voltage lose a meaningful share of the power as heat, and the resulting voltage drop can stop equipment working. The calculator estimates the drop from cable length, size, and current so you can choose a conductor thick enough to keep losses within a few percent — important in 12 V and 24 V systems where even a small absolute drop is a large proportion.

Worked example

A cabin uses 2400 Wh per day with 5 peak sun hours and 80% system efficiency.

  1. Required panel output = 2400 ÷ (5 × 0.8).
  2. = 2400 ÷ 4 = 600 W of panels.
  3. Battery and cable are then sized to the days of autonomy and run length.

About 600 W of panels meets a 2400 Wh daily load at that sun and efficiency.

Frequently asked questions

How many solar panels do I need?

Divide your daily energy use (watt-hours) by the product of peak sun hours and system efficiency to get the panel wattage required. Local peak sun hours and losses to inverters and wiring drive the result.

How do I size a battery for solar storage?

Base it on the energy you must store overnight, the days of autonomy you want for cloudy spells, and the battery's allowable depth of discharge. Lithium tolerates deeper discharge than lead-acid for the same usable capacity.

Why does voltage drop matter in solar wiring?

Low-voltage systems carry high current, so thin or long cables lose significant voltage and power as heat. Sizing the cable to keep the drop within a few percent ensures equipment runs and energy isn't wasted.