Solar Panel System & Savings Calculator
Estimate your required system size, total cost, and annual savings.
How Solar Panel Requirements are Calculated
Calculating the right size for a solar panel system involves balancing your energy consumption with the local solar irradiance available at your property. To get an accurate estimate, we look at three primary metrics: your monthly kilowatt-hour (kWh) usage, your local "Peak Sun Hours," and your roof's orientation.
1. Determining Your Monthly kWh Usage
Your electric bill usually provides a total dollar amount, but the calculator works backward by dividing that bill by your local utility rate. For example, if your bill is $150 and your rate is $0.15 per kWh, you consume 1,000 kWh per month.
2. Peak Sun Hours Explained
Peak sun hours do not refer to how long the sun is in the sky, but rather the intensity of the light. Most regions in the U.S. receive between 3.5 and 6.0 peak sun hours per day. A system in Arizona (high peak hours) will require fewer panels than the same system in Washington (low peak hours) to produce the same amount of energy.
Factors Affecting Installation Costs
| Component | Average Cost Impact | Notes |
|---|---|---|
| Solar Panels | 25-30% of total | Higher efficiency panels cost more but save space. |
| Inverters | 10-15% of total | Micro-inverters are pricier but handle shade better. |
| Labor & Permitting | 30-40% of total | Varies significantly by state and roof complexity. |
Solar Savings Example Calculation
Imagine a homeowner in Florida with the following profile:
- Monthly Bill: $200
- Electricity Rate: $0.13 per kWh
- Daily Sun Hours: 5.2
- Result: This home uses roughly 1,538 kWh per month. To cover 100% of this usage, they would need a 10.5 kW system. At a national average cost of $3.00 per watt, the system would cost $31,500. After the 30% Federal Tax Credit (ITC), the net cost drops to $22,050.
The Federal Solar Tax Credit (ITC)
As of 2024, the federal government offers a 30% Investment Tax Credit for residential solar installations. This is a dollar-for-dollar reduction in the amount of income tax you owe. If your system costs $20,000, you could receive a $6,000 credit on your federal taxes, significantly shortening your ROI period.