Renewable Energy & Efficiency

Renewable energy calculators and formulas for solar, battery storage, and equipment efficiency metrics. Includes solar panel output, battery capacity, and system efficiency calculations.

10Formulas

All levels Difficulty

Updated Jul 2026

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Fundamental

SEER to EER Conversion (Air Conditioner Efficiency)

EER = SEER × 0.875 (approximate) · EER = -0.02 × SEER² + 1.12 × SEER - 0.5 (more precise)

Fundamental

Specific Energy Consumption

SEC = Energy Consumed(kWh) / Output (units)

Fundamental

Lighting Lumen Efficacy

η = Luminous Flux(lm) / Power(W)

Fundamental

Coefficient of Performance (COP)

COP = Useful Heat/Cooling Output / Work Input

Fundamental

Energy Efficiency Ratio (EER)

EER = Cooling Output (BTU/hr) / Power Input (W)

Fundamental

Battery Backup Time

t = Ah / I_load

Fundamental

Battery Energy (Watt-Hours)

Wh = V × Ah

Fundamental

Battery Capacity (Amp-Hours)

Ah = I × t

Fundamental

Number of Solar Panels Needed

N = Total Load Energy / (Panel Output × Sun Hours)

Fundamental

Solar Panel Power Output

P = Irradiance × Area × Efficiency