Solar Panel Savings Calculator

Calculator Inputs

3 columns on large screens, 2 on small, 1 on mobile.

System size (kW)

Typical homes range from 3–12 kW.

Annual kWh per kW

Local solar resource (e.g., 1200–1800).

Performance ratio (0–1)

Accounts for losses, soiling, wiring, and heat.

Installed cost ($)

Turnkey price including equipment and labor.

Rebates & incentives ($)

Upfront discounts or utility rebates.

Tax credit (%)

Optional credit applied to installed cost.

Apply tax credit in year 1

Choose timing for cashflow modeling.

Current rate ($/kWh)

Your retail electricity price today.

Export credit ($/kWh)

Credit for excess generation sent to grid.

Rate escalation (%/yr)

Future price change assumption.

Annual consumption (kWh)

Used to cap self-use savings.

Self-consumption (%)

Share of solar used on-site.

Degradation (%/yr)

Panel output decreases over time.

Annual O&M ($)

Cleaning, monitoring, and minor service.

O&M escalation (%/yr)

Inflation or service cost trend.

Inverter replacement ($)

Optional midlife replacement cost.

Replacement year

Commonly between years 10–15.

Purchase method

Loan uses annual payments for simplicity.

Down payment ($)

Only used when method is loan.

Loan APR (%/yr)

Annual interest rate assumption.

Loan term (years)

Payments stop after this term.

Loan fees ($)

Added to upfront outflow.

Analysis period (years)

Often 20–30 years for panels.

Discount rate (%/yr)

Used to compute NPV.

Reset

Example Scenario Data

A sample configuration to help you validate your inputs.

Item	Example value	Notes
System size	6 kW	Mid-sized residential installation.
Annual kWh per kW	1500	Depends on solar resource and tilt.
Installed cost	$10,500	Before rebates and credits.
Rebates	$500	Utility or program incentive.
Retail rate	$0.20/kWh	Current electricity price.
Export credit	$0.08/kWh	Credit for excess energy.
Self-consumption	70%	Higher with daytime usage or storage.
Degradation	0.5%/yr	Slow performance decline.
O&M	$120/yr	Cleaning and minor service.
Analysis period	25 years	Typical panel life assumption.

Formula Used

Year 1 production (kWh): System kW × kWh per kW-year × Performance ratio
Production with degradation: Prod_y = Prod₁ × (1 − d)^y−1
Electricity rate with escalation: Rate_y = Rate₁ × (1 + e)^y−1
Bill savings: Self-used kWh × Rate_y + Exported kWh × ExportRate_y
Net cashflow: Savings + Credits − O&M − Replacement − LoanPayment
NPV: Σ Cashflow_t / (1 + r)^t using your discount rate.
IRR: the discount rate that makes NPV equal to zero.

These are estimates for comparison and planning, not financial advice.

How to Use This Calculator

Enter your expected system size, production factor, and performance ratio.
Add installed cost, then include rebates and any tax credit percentage.
Set your electricity rate, export credit, and rate escalation assumption.
Choose a self-consumption percentage based on your daytime usage.
Include maintenance and any planned inverter replacement cost.
Select cash or loan, then enter down payment, APR, term, and fees.
Pick an analysis period and discount rate for NPV, then calculate.
Review results, then download CSV or PDF for sharing.

Calculator Inputs

Example Scenario Data

Formula Used

How to Use This Calculator

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