Enter your daily loads and site sun hours. See recommended array, battery bank, and budget. Export results to share with installers and lenders easily.
Use these sample inputs to sanity-check your results.
| Scenario | Daily kWh | Sun Hours | Autonomy (days) | Voltage | DoD | Panel (W) |
|---|---|---|---|---|---|---|
| Cabin weekend | 3.5 | 4.0 | 2 | 24 | 50% | 400 |
| Small home | 8.0 | 4.5 | 2 | 48 | 50% | 400 |
| Remote workshop | 14.0 | 5.5 | 3 | 48 | 60% | 450 |
1) Daily energy: DailyWh = DailykWh × 1000
2) Overall efficiency: Eff = InverterEff × BatteryEff × ControllerEff × (1 − MiscLosses)
3) PV array watts: PVW = DailyWh ÷ (SunHours × Eff), then a design buffer is applied and panels are rounded up.
4) Battery energy: BattWh = (DailyWh × AutonomyDays) ÷ DoD ÷ BatteryEff
5) Battery capacity: BattAh = BattWh ÷ SystemVoltage
6) Controller current: Amps = (PVWatts ÷ Voltage) × 1.25 (safety factor).
7) Discounted LCOE: Present value of costs divided by present value of kWh, with annual maintenance and panel degradation.
Off‑grid sizing starts with daily kWh and peak power. Multiply daily kWh by 1,000 to get watt‑hours, then compare peak and surge watts to choose an inverter with headroom. A realistic peak figure prevents nuisance shutdowns when pumps or compressors start. If your usage varies, size to the higher season and treat the lower season as surplus for extra flexibility.
Array size depends on peak sun hours and system efficiency. The calculator multiplies inverter, battery, and controller efficiencies, then applies a loss allowance for wiring, heat, and soiling. It also adds a buffer so production still covers cloudy streaks and seasonal swings. In practical terms, a one‑hour drop in sun hours can require 20–30% more array capacity.
Storage is driven by autonomy days and allowable depth of discharge. Required battery watt‑hours equals daily watt‑hours times autonomy, divided by usable DoD and round‑trip efficiency. Converting watt‑hours to amp‑hours using system voltage helps map results to common battery modules. Choosing a lower DoD typically increases initial capacity, but it can extend cycle life and reduce replacement frequency.
Charge controllers must safely handle current. A simple estimate uses array watts divided by system voltage, then adds a safety factor. Higher voltage systems reduce current, cable size, and resistive losses, which can lower balance‑of‑system costs on longer runs. Verify that your controller input voltage rating matches panel string voltage in cold weather, when Voc rises.
Upfront cost combines PV, storage, inverter, controller, and a balance‑of‑system percentage. Annual maintenance is modeled as a percent of upfront cost. Discounted levelized cost divides present‑value costs by discounted lifetime kWh, reduced by degradation. Payback compares net annual savings to upfront investment using your avoided energy price. For remote sites, include fuel delivery costs in the avoided price.
List each device’s watts and hours used per day. Convert to kWh by watts × hours ÷ 1,000, then add them up. Use a safety margin for unexpected loads and future additions.
Use an annual average for quick planning, but size conservatively using the lowest-season value if reliability matters. Local solar maps often publish monthly peak sun hours for fixed-tilt arrays.
Solar output varies with clouds, heat, panel mismatch, and soiling. A design buffer helps the array meet your daily energy target more consistently, reducing deep battery cycling and generator runtime.
Small systems often use 12V, moderate systems 24V, and larger systems 48V or higher. Higher voltage lowers current, improves efficiency, and can reduce cable size and voltage drop.
No. Usable energy depends on depth of discharge and efficiency. A 10 kWh battery at 50% DoD provides about 5 kWh usable before losses. Adjust DoD for your battery chemistry.
It can. Compare the system’s net annual value to what you would otherwise spend on fuel, oil changes, hauling, and replacement generators. Enter that effective cost per kWh as avoided energy cost.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.