Solar Panel Cost Savings Calculator
Project your total 25-year net savings from going solar, accounting for electricity rate inflation and panel degradation. Use this before getting installer quotes to set realistic financial expectations.
About this calculator
The net savings formula accounts for rising electricity rates, gradual panel degradation, and the upfront cost after the federal tax credit: Net Savings = (monthlyElectricBill × 12) × (1 + electricityRateIncrease/100) × (1 − systemEfficiencyLoss/100) × 25 − (systemCost − systemCost × federalTaxCredit/100). The first term estimates total electricity costs avoided over 25 years, scaled upward by the expected annual rate increase and downward by cumulative panel efficiency loss. The second term is the net out-of-pocket cost after the federal Investment Tax Credit. A positive result means solar saves money over the panel lifetime; higher electricity rate increases and lower net system costs improve the outcome most dramatically.
How to use
Monthly bill: $150. System cost: $18,000. Federal tax credit: 30%. Annual rate increase: 3%. Annual efficiency loss: 0.5%. Net cost = $18,000 − ($18,000 × 0.30) = $12,600. Gross savings = ($150 × 12) × (1 + 0.03) × (1 − 0.005) × 25 = $1,800 × 1.03 × 0.995 × 25 = $1,800 × 25.7 ≈ $46,264. Net savings = $46,264 − $12,600 = $33,664 over 25 years. Simple payback ≈ $12,600 / $1,800 ≈ 7 years.
Frequently asked questions
How does the annual electricity rate increase affect solar savings projections?
Electricity prices in the US have risen an average of 2–4% per year over the past two decades, and this inflation significantly boosts the value of solar over time. Even a 3% annual increase means electricity costs roughly double every 24 years. Because your solar panels lock in a fixed energy cost at installation, every rate hike increases the value of the electricity they generate. Sensitivity analysis shows that changing the rate increase assumption from 2% to 4% can raise projected 25-year savings by 20–30%.
What is the typical payback period for residential solar panels in the US?
The average payback period for residential solar in the US is 6–10 years, depending on system cost, local electricity rates, and available incentives. States with high electricity prices like California, Massachusetts, and Hawaii typically see payback periods of 5–7 years. States with low electricity rates and fewer incentives may see 10–12 year paybacks. After payback, the panels continue generating essentially free electricity for the remaining 15–20 years of their life, delivering the bulk of total financial returns.
Why does system efficiency loss matter when calculating long-term solar savings?
Solar panels degrade over time due to UV exposure, temperature cycling, and material aging, typically losing 0.5–0.7% of their rated output per year. After 25 years at 0.5%/year degradation, a panel produces about 88% of its original output. This means your system generates slightly less electricity — and therefore avoids slightly less cost — each successive year. Ignoring degradation overstates 25-year savings by roughly 6–10%. Premium panels from Tier-1 manufacturers often come with linear power warranties guaranteeing no more than 0.5%/year degradation.