Methodology
Engineering Methodology
Every SolarCalcKit result is produced by a deterministic, client-side calculation engine with fully documented formulas, inputs, outputs, assumptions and limitations. Nothing is applied silently.
Deterministic calculations
Identical inputs always produce an identical result. There is no randomness and no hidden state — the same values always come back the same way.
Client-side execution
All mathematics run entirely in your browser. No calculation data is ever sent to a SolarCalcKit server; copy, Markdown and PDF reports are generated locally from the same computed values.
Documented assumptions
Every applied assumption — a chemistry depth-of-discharge default, an inverter efficiency, a conductor resistivity — carries an explicit basis and is echoed into the result so you always know what was used. User overrides replace the default and are flagged as such.
No hidden margins
The engines never invent safety factors. Physical counts (series, strings, batteries) are rounded up because you cannot build a partial string — that surplus is always reported, never hidden.
Validation philosophy
Results are engineering aids and estimates for planning, not certified designs. Always verify them against component datasheets and applicable electrical codes (NEC, IEEE) with a qualified professional before installation.
Calculator specifications
Formulas, units, inputs and assumptions by tool
Each calculator's exact equations, units, inputs, outputs, assumptions and limitations — reflected verbatim from its engine definition.
1 · Solar Load Calculator
Open tool →Formulas & units
- E_i [Wh/day] = P_i [W] × qty_i × hours_i
- E_total [Wh/day] = Σ E_i
- E_total [kWh/day] = E_total / 1000
- P_connected [W] = Σ (P_i × qty_i)
Inputs
Per-appliance power (W), quantity, and hours per day.
Outputs
Daily energy per load and total (Wh & kWh), connected load (W).
Assumptions
- User-supplied wattages are used as entered.
- No efficiency, safety margin, or derating factor is applied.
- Energy (Wh) is kept distinct from power (W).
Limitations
- No downstream battery / MPPT / inverter / wire sizing.
- Assumes loads run for the stated hours every day — re-check with measured data.
2 · Solar Battery Calculator
Open tool →Formulas & units
- E_autonomy [Wh] = E_daily × autonomy days
- E_usable [Wh] = E_autonomy / η_inverter
- E_nominal [Wh] = E_usable / DoD
- series = V_system / V_battery
- strings = ⌈E_nominal / V_system ÷ Ah_battery⌉
- total = series × strings
Inputs
Daily energy (kWh), autonomy (days), system & battery voltage (V), battery capacity (Ah), chemistry, DoD, inverter efficiency.
Outputs
Required bank energy (Wh), series, parallel strings, total batteries, bank capacity (Ah), nominal energy (Wh).
Assumptions
- Chemistry DoD defaults: LiFePO4/NMC 0.8; AGM/gel/flooded lead-acid 0.5.
- Inverter efficiency default 0.90 (CEC basis), user-overridable; use 1 for DC-coupled.
- Strings rounded up — a partial string cannot be built.
Limitations
- Battery-internal round-trip losses are not modeled separately.
- Lead-acid banks > 2 days autonomy risk sulfation.
- Battery voltage must divide system voltage exactly.
3 · Battery Bank Calculator
Open tool →Formulas & units
- series = V_system / V_battery
- Ah_req = target (Ah) or target (kWh) × 1000 / V_system
- strings = ⌈Ah_req / Ah_battery⌉
- total = series × strings
- bank_V = series × V_battery
- bank_Ah = strings × Ah_battery
Inputs
System & battery voltage (V), battery capacity (Ah), sizing mode (target kWh or target Ah).
Outputs
Series, parallel strings, total batteries, bank voltage, bank capacity (Ah), nominal energy (Wh), surplus Ah, configuration label (e.g. 4S2P).
Assumptions
- Applies no depth of discharge, no efficiency, and no safety margins.
- Converts a stated target into a whole-battery configuration only.
Limitations
- Whole batteries only; battery voltage must divide system voltage.
- Many parallel strings (> ≈4) risk uneven charging — reported as a warning.
4 · MPPT Calculator
Open tool →Formulas & units
- I_out [A] = P_pv [W] / V_system [V]
- Voc_cold = Voc_stc × (1 + β/100 × (T_min − 25))
Inputs
PV array power (W), system voltage (V), array Voc (V), array Vmp (V), minimum temperature (°C), Voc temperature coefficient (%/°C).
Outputs
Required output current (A), cold-corrected Voc (V), array Vmp (V), array Voc STC (V).
Assumptions
- No controller efficiency is applied (product-specific, typically 95–99%).
- Buck converters step down only — array Vmp must exceed battery voltage.
Limitations
- Manufacturer max PV input is not assumed — verify against the datasheet.
- Cold-Voc requires the panel's temperature coefficient.
5 · Solar Wire Size Calculator
Open tool →Formulas & units
- R [Ω] = ρ × (2 × L) / A
- V_drop [V] = I × R
- V_drop [%] = V_drop / V_system × 100
- A_req [mm²] = (2 × L × I × ρ) / V_drop_allowed
Inputs
Current (A), one-way length (m), system voltage (V), allowable drop (%), conductor material (copper/aluminum), optional selected area (mm²).
Outputs
Required standard area (mm², IEC 60228), resistance (Ω), voltage drop (V & %), applied area (mm²).
Assumptions
- 20 °C resistivity: copper 0.0172, aluminum 0.0282 Ω·mm²/m (IEC 60228).
- P_cont [W] = Σ continuousW
- P_peak [W] = P_cont + Σ surgeW
- recommended = ⌈P_cont / 50⌉ × 50
- I_dc [A] = P_out / (V_system × η)
- No invented startup multiplier — surge is user-supplied.
- Solar Load Calculator Audit daily energy consumption appliance by appliance.
- Solar Battery Calculator Size a battery bank from daily energy use, autonomy, chemistry and depth of discharge.
- Battery Bank Calculator Convert a target bank size into an exact series–parallel configuration.
- MPPT Calculator Size a solar charge controller from PV array wattage and battery voltage.
- Solar Wire Size Calculator Size DC conductors from current, run length and acceptable voltage drop.
- Inverter Calculator Size an inverter from continuous and surge loads at your system voltage.
6 · Inverter Calculator
Open tool →Formulas & units
Inputs
Per-load continuous (W) and surge (W, optional), system voltage (V), inverter efficiency (optional).
Outputs
Continuous total, surge total and peak (W), minimum & recommended continuous rating (W), DC current continuous & peak (A).