We take the appliances and usage you enter and turn those into meaningful system-sizing recommendations. Below is what each figure means and exactly how it’s calculated.

1. Daily Consumption (kWh)

Daytime kWh

Daytime kWh = (quantity × wattage in W × hours used in daytime) ÷ 1,000

Converts total watt-hours into kilowatt-hours.

Nighttime kWh

Nighttime kWh = (quantity × wattage in W × hours used at night) ÷ 1,000

Total Daily kWh

Total kWh = Daytime kWh + Nighttime kWh

Note: Day + Night hours per appliance cannot exceed 24 hours. The calculator validates this automatically.

 

2. Solar Panel Count

Energy per panel per day

Energy per panel = (panel wattage in W ÷ 1,000) × sun hours per day

e.g. a 600 W panel × 5 sun hours = 3 kWh/day.

Raw panels needed

Raw panels = Total kWh ÷ Energy per panel

Important: We use Total kWh (day + night combined), not just daytime consumption. The panels must generate enough energy to power your daytime appliances and charge the batteries for nighttime use.

Apply system losses

Loss factor = 1 + (loss percentage ÷ 100)

Default is 25% (loss factor = 1.25). This covers wiring losses (~2–3%), inverter inefficiency (~5–10%), dust and soiling (~2–5%), temperature derating (~5–15%), and panel mismatch (~1–2%). You can adjust this percentage in the settings.

Panels with losses = Raw panels × Loss factor

Round up (always size up to the next whole panel):

Panels needed = ceil(Panels with losses)

ceil(3.2) = 4

Total system wattage

Total system wattage = Panels needed × Panel wattage

 

3. Battery Sizing

Battery sizing depends on three factors: your nighttime consumption, how many days of backup (autonomy) you need, and your battery chemistry.

Battery type parameters

Battery Type	Depth of Discharge (DoD)	Round-Trip Efficiency
Lithium (LiFePO4)	80%	95%
Lead-Acid (AGM/GEL)	50%	85%

Depth of Discharge (DoD) is how much of the battery’s capacity you can safely use. Draining a lead-acid battery below 50% dramatically shortens its lifespan, while lithium batteries can safely use 80% of their capacity.

Round-trip efficiency accounts for energy lost as heat during charging and discharging. If you store 1 kWh, you only get back 0.95 kWh (lithium) or 0.85 kWh (lead-acid).

Storage required (kWh)

Battery kWh = (Nighttime kWh × Autonomy days) ÷ (DoD × Efficiency)

Autonomy days (default: 1) is how many days without sun your batteries should cover. For off-grid systems in cloudy regions, 2–3 days is recommended.

Example: 5 kWh nighttime usage, 1 autonomy day, Lithium:

Battery kWh = (5 × 1) ÷ (0.80 × 0.95) = 5 ÷ 0.76 = 6.58 kWh

Battery bank size (Ah)

Battery Ah = (Battery kWh × 1,000) ÷ Battery Voltage

Then round up:

Battery Bank Size = ceil(Battery Ah)

4. Inverter Size (kW)

The inverter must handle your peak simultaneous load — the maximum wattage of all appliances that could run at the same time. This is not an average; it’s the worst-case moment.

Peak load

Peak load (W) = SUM of (quantity × wattage) for all appliances

Apply 30% safety margin to cover motor startup surges. Appliances with motors (refrigerators, air conditioners, pumps, washing machines) can draw 3–5× their rated wattage for a few seconds when starting up.

Inverter size = ceil(Peak load × 1.30 ÷ 1,000)

Example: If your appliances total 3,400 W peak:

Inverter size = ceil(3,400 × 1.30 ÷ 1,000) = ceil(4.42) = 5 kW

We recommend a pure sine wave inverter for sensitive electronics and motor-driven appliances.

 

5. Charge Controller (MPPT)

The charge controller regulates the power flowing from the solar panels to the batteries. We size an MPPT (Maximum Power Point Tracking) controller, which is more efficient than PWM types.

Controller current rating

Controller Amps = ceil((Total system wattage ÷ Battery Voltage) × 1.25)

The 25% safety margin accounts for peak production conditions (cold, clear days when panels can exceed their rated output).

Example: 6 panels × 600 W = 3,600 W system at 24 V:

Controller Amps = ceil((3,600 ÷ 24) × 1.25) = ceil(187.5) = 188 A

For large systems, you may need multiple charge controllers wired in parallel.

 

6. Estimated Daily Production (kWh)

This shows how much energy your sized solar array is expected to generate per day (before losses):

Daily Production = (Total system wattage ÷ 1,000) × Sun hours per day

This value will always be somewhat higher than your Total kWh consumption because the system is oversized to account for losses.

 

Settings You Can Adjust

Setting	Default	What It Does
Panel Wattage	600 W	Rated power of a single solar panel
Battery Voltage	24 V	System voltage (12V, 24V, or 48V)
Average Sun Hours	5 hrs	Peak sun hours per day for your location
Battery Type	Lithium	Determines DoD and efficiency values
Autonomy Days	1 day	Days of battery backup without sun
System Losses	25%	Covers wiring, heat, dust, inverter losses

Your results update instantly when you change any setting.