📖 Overview
Calculate how many kilowatts of solar panels you need based on your energy usage and local insolation.
🧪 Example Scenarios
Use these default and higher-pressure example inputs to explore how sensitive this calculator is before using your real numbers.
| Input | Base Case | Higher Pressure Case |
|---|---|---|
| Monthly Bill ($) | 150 | 172.5 |
| Price per kWh ($) | 0.15 | 0.18 |
| Sun Hours per Day | 5.5 | 6.6 |
| System Cost per Watt ($) | 3 | 3.6 |
⚙️ How It Works
Estimates the required solar panel system size in kilowatts and the estimated installation cost based on your monthly electricity bill, local electricity rate, and peak sun hours.
The Formula
System kW = Daily kWh Usage ÷ Peak Sun Hours
💡This calculator is scenario-based. Better input quality leads to better decision quality.
Quick Reference
| Input | Example Value |
|---|---|
| Monthly Bill ($) | 150 |
| Price per kWh ($) | 0.15 |
| Sun Hours per Day | 5.5 |
| System Cost per Watt ($) | 3.00 |
When To Use This
- Use this tool when you need a fast decision during active planning or execution.
- Use this before committing money, time, or tradeoffs that are hard to reverse.
- Use this to compare options using the same assumptions across scenarios.
Edge Cases To Watch
- Results can be misleading if key inputs are missing, stale, or unrealistic.
- Very small or very large values may amplify rounding effects and interpretation risk.
- If assumptions change mid-decision, recalculate before acting.
Practical Tips
💡 The Federal Solar Investment Tax Credit (ITC) currently offers a 30% tax credit on installation costs.
💡 Peak sun hours vary significantly by location — the US Southwest averages 5–6.5 hours vs 3–4 in the Northeast.
💡 Get at least 3 quotes from local installers since per-watt prices vary considerably.
Frequently Asked Questions
❓ Does this include battery storage?
No. This estimates a grid-tied system only. Adding battery backup like a Tesla Powerwall adds $10,000–$15,000+.
❓ How long until solar pays for itself?
Typical payback periods are 6–12 years in the US, depending on local electricity rates, sun hours, and incentives.