How the Solar Calculator Works

What you get from the tool

• Recommended solar panels (count): how many panels you likely need to cover typical daily energy use.
• Recommended battery (kWh): a planning-level battery size for night usage and optional backup nights.
• Peak load (kW): a reasonable estimate of “how much power at once” your home might draw.
• Inverter guidance: inverter class suggestions based on peak load, backup preference, and your setup style.

The goal is to give you a fast starting point for research and installer conversations — not a binding engineering design.

What you enter

1. Country (and region if available): used to estimate average daily sun hours (a “solar resource” baseline).
2. Appliances + hours: select common appliances, then set how many hours they run in the day and at night.
3. Panel wattage: e.g., 400W panels (slider).
4. System efficiency: an “all-in” factor that bundles real-world losses (inverter, wiring, temperature, etc.).
5. Battery round-trip efficiency: accounts for energy lost during charge/discharge.
6. Nights of electricity supply (storage): how many nights of backup you want from the battery.

You can get useful results quickly even with rough usage estimates — then refine later as you learn more.

Step-by-step calculation logic

1) Energy demand (Wh and kWh)

For each appliance, the tool multiplies its typical wattage by the hours you set for day and night. It then sums everything into:

• Day energy (Wh)
• Night energy (Wh)
• Total daily energy (Wh)

2) Battery size (kWh) for backup nights

If you want backup, the calculator starts from your night-time energy and scales it by the number of backup nights. Then it adjusts for two realities:

• Depth of discharge (DoD): batteries are rarely used from 100% to 0% in practice.
• Round-trip efficiency: you lose some energy when charging/discharging.

3) Solar panels (count)

Panel count is based on how much energy your panels can produce in a typical day in your location. That depends on:

• Panel wattage (W)
• Sun hours (hours/day)
• System efficiency (0–1), to reflect real-world losses

4) Peak load (kW) and inverter guidance

Peak load is an estimate of “how many watts might be running at once.” Homes rarely run every appliance at the same time, so the calculator applies a conservative diversity approach to avoid over-sizing based on an unrealistic worst-case.

• Peak load (kW) helps size the inverter so it can handle simultaneous usage.
• Inverter recommendations factor in your load profile and whether you want backup capability.

Inverter sizing can get nuanced (motor start surges, EV charging strategy, three-phase vs single-phase, code requirements). The tool’s goal is to get you into the right ballpark quickly.

Assumptions and what’s intentionally simplified

To keep the calculator fast and beginner-friendly, it makes a few assumptions that are reasonable for first-pass sizing:

• Sun hours are averaged: great for planning, but real production varies by season and weather.
• Efficiency is bundled: instead of modeling every loss separately, you set one overall system efficiency.
• Appliance wattages are typical: your actual devices may be higher/lower depending on model and usage.
• Shading and roof geometry are not modeled: these require site-specific analysis.

If you want a more conservative estimate, lower the system efficiency and increase backup nights.

Accuracy notes and limitations

Treat results as an estimate for planning and education. For a final design, installers typically evaluate:

• Roof orientation, tilt, usable area, and shading throughout the day/year
• Local electrical standards (grid-tie rules, breaker limits, export constraints)
• Battery chemistry, warranty constraints, and operating temperature range
• Large transient loads (HVAC compressors, well pumps, workshop tools)

Best next step: use the calculator output as a starting spec, then compare with 2–3 installer proposals.