Why Compare Community and Rooftop Solar?
Rooftop solar has long been the gold standard for homeowners seeking lower energy bills and greener power. However, millions of people cannot install panels because they rent, live in shaded areas, or face structural limitations. Community solar subscriptions, which allocate a portion of a shared solar farm's production to a customer, have emerged as an alternative. Subscribers receive credits on their utility bills for the energy generated. They avoid upfront equipment costs but pay a per-kWh rate and often a small annual fee. This calculator puts community solar and rooftop ownership side by side so you can evaluate which path offers the lower annual cost for your specific usage.
The rise of community solar addresses equity concerns in renewable energy adoption. Renters, condo dwellers, and low-income households can participate without a roof. Utilities and third-party developers increasingly offer subscriptions with modest discounts below utility rates. Yet those savings might pale compared to the long-term benefits of owning panels if you have the means and suitable property. By quantifying both options, the tool helps households make informed decisions about joining a community solar program or investing in a rooftop system.
How the Calculation Works
The annual cost of community solar is straightforward: multiply your annual electricity usage by the subscription rate and add any annual administrative fee. Rooftop solar involves spreading the installation cost across the system's lifespan and adding expected annual maintenance like cleaning or inverter replacement reserves. The calculator assumes the rooftop system offsets your entire annual usage; if it generates less, real costs would include residual grid consumption. Results display each approach's annual cost and the difference between them, revealing the more economical choice over time.
The formula for annual rooftop solar cost is:
Where is the installation cost, is system lifespan in years, and is annual maintenance cost. Community solar annual cost is:
Where is annual usage and is the community solar rate per kWh, with representing any subscription fee. The difference displayed is .
Worked Example
Imagine a household using 8,000 kWh annually. A community solar provider offers energy at $0.11 per kWh with a $20 yearly fee. The annual cost becomes 8,000 × $0.11 + $20 = $900. A rooftop system sized to meet the same demand costs $20,000 to install, is expected to last 25 years, and needs $200 per year in maintenance and inverter reserves. The annualized cost is $20,000 / 25 + $200 = $1,000. In this scenario, community solar appears cheaper by $100 per year. However, if installation costs drop to $15,000 or incentives reduce the net price, rooftop ownership could win over the long term. This demonstrates the importance of customizing assumptions for your situation.
Scenario Comparison
The first table explores how community solar rates influence annual costs for an 8,000 kWh household with a $20 fee.
| Rate ($/kWh) | Annual Community Cost ($) |
|---|---|
| 0.09 | 740.00 |
| 0.11 | 900.00 |
| 0.13 | 1,060.00 |
The second table varies rooftop installation cost while keeping lifespan at 25 years and maintenance at $200.
| Install Cost ($) | Annual Rooftop Cost ($) |
|---|---|
| 15,000 | 800.00 |
| 20,000 | 1,000.00 |
| 25,000 | 1,200.00 |
Limitations and Assumptions
This calculator assumes your rooftop system offsets 100% of usage and ignores financing costs. Real installations may rely on loans with interest, or produce less than expected due to shading, orientation, or degradation. Maintenance costs are treated as a flat annual value though major component replacements may occur intermittently. Community solar contracts can include escalators, early termination fees, or credit rate variations tied to utility prices. The model does not account for tax credits, renewable energy certificates, or net metering payouts that can significantly change rooftop economics. Users should adjust inputs based on actual quotes and contract terms.
Environmental and community benefits are mentioned qualitatively. Community solar often supports local jobs and expands access to clean energy, while rooftop installations can increase property value and provide backup power when paired with batteries. Regulatory frameworks also vary widely by region, affecting interconnection costs and credit valuations. Therefore, treat the results as a starting point rather than a definitive financial plan.
Further Reading
To dive deeper into ownership economics, explore the solar roof payback calculator or compare hybrid solutions with the solar battery payback calculator. If you are evaluating other renewable options, the solar vs home wind system cost calculator offers additional context.