Solar Panel Calculator
Calculate solar system size, panel count, and annual energy production. Size by energy usage or available roof space with regional sun hour adjustments.
Energy Usage
System Size
9.6 kW
Solar Panel Wattage Guide
- 250-300W
- Lower efficiency
- More roof space needed
- 350-400W
- Best value
- Most common choice
- 400-450W
- Highest efficiency
- Limited roof space
- South-facing roofs produce 15-25% more than east/west orientations
- Shade from trees or buildings can reduce output by 10-25%
- Get 3+ quotes - prices vary significantly between installers
- Check local incentives in addition to the federal tax credit
- Consider future usage growth (EV, heat pump) when sizing
Related Calculators
About This Calculator
How many solar panels does your home actually need? The average American home requires 15-25 panels to offset electricity usage, but the exact number depends on your energy consumption, roof space, local sun exposure, and panel efficiency. This Solar Panel Calculator determines your optimal system size, panel count, annual production, and total project cost.
2026 solar market reality: The solar industry faces a major shift. The 30% federal Residential Clean Energy Credit was eliminated on December 31, 2025, through the "One Big Beautiful Bill Act." Systems installed in 2026 no longer qualify for the homeowner tax credit—a significant change from the IRA's original schedule through 2032. However, solar leases and PPAs still offer tax benefits through 2027 via the commercial 48E credit.
Current solar costs: Despite the tax credit loss, solar installation costs continue to decline. The national average is $2.50-$3.00 per watt installed, meaning an 11 kW system costs approximately $27,500-$33,000. Without the 30% credit, payback periods have extended from 7-9 years to 10-14 years in most markets—but solar still makes long-term financial sense in many regions.
Why go solar in 2026? Rising electricity rates (averaging 4-5% annually), energy independence, increased home value (3-4% premium), and environmental impact remain compelling. This calculator helps you determine if solar math works for your specific situation.
How to Use the Solar Panel Calculator
- 1**Enter your monthly electricity usage**: Find this on your utility bill (measured in kWh). Average US home uses 900-1,000 kWh/month.
- 2**Select your geographic region**: Sun exposure varies dramatically—Southwest gets 6+ peak sun hours while Northeast gets 3.5-4.
- 3**Set your target offset percentage**: 100% offsets all usage; some choose 80-90% to optimize cost vs. benefit.
- 4**Choose your panel wattage**: Standard panels are 400W; premium panels reach 450W but cost more.
- 5**Enter roof constraints (if applicable)**: Usable roof space affects maximum system size.
- 6**Review system sizing**: See recommended kW size, panel count, and annual production estimate.
- 7**Enable Advanced mode**: Customize electricity rates, installation costs, and financing options for detailed ROI analysis.
- 8**Compare scenarios**: Calculate with/without battery storage, different financing options, and production estimates.
Formula
System Size (kW) = Annual kWh Usage ÷ (Peak Sun Hours × 365 × 0.80)
Number of Panels = System Size (watts) ÷ Panel Wattage
Annual Production = System Size (kW) × Peak Sun Hours × 365 × 0.80
Simple Payback = Net System Cost ÷ Annual Electricity SavingsThe solar sizing formula divides your annual electricity usage by production capacity. Peak sun hours (3.5-6.5 depending on location) multiplied by 365 days and the 0.80 efficiency factor (accounting for inverter loss, temperature, soiling, and degradation) gives annual production per kW installed. Panel count is simply total watts divided by individual panel wattage. Payback period divides total cost by annual savings at your electricity rate.
Solar Panel System Sizing Guide
The Core Sizing Formula:
System Size (kW) = Annual kWh Usage ÷ (Peak Sun Hours × 365 × 0.80)
The 0.80 factor accounts for real-world losses: inverter efficiency (96%), temperature degradation (5%), soiling (2%), wiring losses (2%), and system aging (1%).
Typical System Sizes by Home:
| Monthly Usage | Annual kWh | System Size | 400W Panels | Production |
|---|---|---|---|---|
| 500 kWh | 6,000 | 4 kW | 10 panels | 5,800-7,000 kWh |
| 750 kWh | 9,000 | 6 kW | 15 panels | 8,700-10,500 kWh |
| 1,000 kWh | 12,000 | 8 kW | 20 panels | 11,600-14,000 kWh |
| 1,500 kWh | 18,000 | 12 kW | 30 panels | 17,400-21,000 kWh |
| 2,000 kWh | 24,000 | 16 kW | 40 panels | 23,200-28,000 kWh |
| 3,000 kWh | 36,000 | 24 kW | 60 panels | 34,800-42,000 kWh |
System Size vs. Roof Space Required:
| System Size | Panels (400W) | Roof Area Needed | Approximate Output |
|---|---|---|---|
| 4 kW | 10 | 180-200 sq ft | 5,800-6,400 kWh/yr |
| 8 kW | 20 | 360-400 sq ft | 11,600-12,800 kWh/yr |
| 12 kW | 30 | 540-600 sq ft | 17,400-19,200 kWh/yr |
| 16 kW | 40 | 720-800 sq ft | 23,200-25,600 kWh/yr |
Important Sizing Considerations:
- Electric vehicles add 3,000-4,500 kWh/year per vehicle
- Heat pumps add 2,000-4,000 kWh/year depending on climate
- Pool pumps add 2,000-3,000 kWh/year
- Size for future needs—adding panels later is less cost-effective
2026 Solar Costs and Financial Analysis
Current Installation Costs (2026):
| System Size | Cost per Watt | Gross Cost | Net Cost (2026)* |
|---|---|---|---|
| 6 kW | $2.75-3.25 | $16,500-19,500 | $16,500-19,500 |
| 8 kW | $2.65-3.15 | $21,200-25,200 | $21,200-25,200 |
| 10 kW | $2.55-3.05 | $25,500-30,500 | $25,500-30,500 |
| 12 kW | $2.50-3.00 | $30,000-36,000 | $30,000-36,000 |
| 16 kW | $2.45-2.95 | $39,200-47,200 | $39,200-47,200 |
*The 30% federal tax credit no longer applies to residential installations after 12/31/2025.
Before vs. After Tax Credit Elimination:
| 10 kW System | Before (2025) | After (2026) | Difference |
|---|---|---|---|
| Gross cost | $28,000 | $28,000 | $0 |
| Federal credit | -$8,400 | $0 | +$8,400 |
| Net cost | $19,600 | $28,000 | +$8,400 |
| Simple payback | 7-9 years | 10-14 years | +3-5 years |
Financing Options:
| Option | Rate (2026) | Pros | Cons |
|---|---|---|---|
| Cash purchase | N/A | Lowest total cost, own system | High upfront cost |
| Solar loan | 6-9% APR | Own system, spread payments | Interest adds to cost |
| HELOC | 8-9% APR | Tax-deductible interest | Home as collateral |
| Lease | Fixed payment | No upfront cost, maintenance included | Don't own system |
| PPA | $/kWh rate | Pay only for production | Long-term contract |
2026 Lease/PPA Advantage:
With homeowner credits eliminated, solar leases and PPAs now offer a unique advantage: the commercial 48E tax credit remains available through 2027. Leasing companies can pass some savings to customers, making leases more competitive vs. purchase in 2026.
Peak Sun Hours by Location
US Regional Peak Sun Hours:
| Region | Peak Sun Hours | Annual Factor | Example Cities |
|---|---|---|---|
| Desert Southwest | 6.0-7.0 hrs | Excellent | Phoenix, Las Vegas, Tucson |
| California | 5.0-5.8 hrs | Very Good | LA, San Diego, Sacramento |
| Mountain West | 5.0-5.5 hrs | Very Good | Denver, Salt Lake City |
| Southern Plains | 5.0-5.5 hrs | Very Good | Dallas, Austin, Oklahoma City |
| Southeast | 4.5-5.2 hrs | Good | Atlanta, Miami, Charlotte |
| Mid-Atlantic | 4.0-4.5 hrs | Average | DC, Philadelphia, Baltimore |
| Midwest | 4.0-4.5 hrs | Average | Chicago, Indianapolis, St. Louis |
| Northeast | 3.5-4.2 hrs | Below Average | Boston, NYC, Hartford |
| Pacific Northwest | 3.5-4.0 hrs | Below Average | Seattle, Portland |
| Alaska | 2.5-4.5 hrs | Variable | Varies by season dramatically |
Production Multiplier by State (vs. Arizona baseline):
| State | Production Factor | 1 kW Produces |
|---|---|---|
| Arizona | 100% | 1,850 kWh/year |
| California | 92% | 1,700 kWh/year |
| Texas | 90% | 1,665 kWh/year |
| Florida | 85% | 1,570 kWh/year |
| Colorado | 88% | 1,630 kWh/year |
| Georgia | 80% | 1,480 kWh/year |
| Ohio | 72% | 1,330 kWh/year |
| New York | 70% | 1,295 kWh/year |
| Massachusetts | 68% | 1,260 kWh/year |
| Washington | 65% | 1,200 kWh/year |
Beyond Sun Hours—Other Factors:
| Factor | Impact | Optimization |
|---|---|---|
| Roof orientation | South is best | East/West still 80-90% |
| Roof pitch | 30-45° ideal | Flat roofs use tilt mounts |
| Shading | Reduces output significantly | Microinverters help |
| Temperature | Hot = less efficient | Good airflow helps |
| Snow cover | Temporary reduction | Snow slides off tilted panels |
Panel Selection and Technology
Solar Panel Types (2026):
| Type | Efficiency | Cost | Lifespan | Best For |
|---|---|---|---|---|
| Monocrystalline | 20-24% | High | 30-35 yrs | Limited space, maximum output |
| Polycrystalline | 15-18% | Low | 25-30 yrs | Budget installations |
| Thin-film | 10-13% | Lowest | 20-25 yrs | Commercial, curved surfaces |
| N-type mono | 22-24% | Highest | 30-35 yrs | Premium residential |
Panel Wattage Comparison:
| Wattage | Efficiency | Physical Size | Panels for 8 kW | Cost/Panel |
|---|---|---|---|---|
| 300W | 18% | 65" × 39" | 27 panels | $150-200 |
| 350W | 19% | 67" × 40" | 23 panels | $175-225 |
| 400W | 21% | 69" × 41" | 20 panels | $200-275 |
| 450W | 22% | 74" × 41" | 18 panels | $275-350 |
Top Panel Brands (2026):
| Brand | Origin | Warranty | Efficiency | Price Tier |
|---|---|---|---|---|
| SunPower | USA | 25 yr | 22.8% | Premium |
| REC | Norway | 25 yr | 22.3% | Premium |
| Panasonic | Japan | 25 yr | 22.2% | Premium |
| LG | Korea | 25 yr | 21.7% | Premium |
| Q Cells | Korea/USA | 25 yr | 21.4% | Mid-tier |
| Canadian Solar | Canada | 25 yr | 21.0% | Value |
| JinkoSolar | China | 25 yr | 21.3% | Value |
| Trina Solar | China | 25 yr | 21.0% | Budget |
Inverter Options:
| Type | Cost | Pros | Cons |
|---|---|---|---|
| String inverter | $1,000-2,000 | Lower cost, simple | Shading affects all panels |
| Microinverters | $150-250/panel | Panel-level optimization | Higher cost, more components |
| Optimizers + string | $50-100/panel | Best of both | Mid-range cost |
| Hybrid (with battery) | $3,000-5,000 | Battery-ready | Highest cost |
State Incentives and Net Metering (2026)
State Solar Incentives (With Federal Credit Gone):
| State | State Credit/Rebate | Net Metering | Other Incentives |
|---|---|---|---|
| California | None | NEM 3.0 (reduced) | Property tax exemption |
| Arizona | None | Declining avoided cost | SREC market |
| Texas | None | Varies by utility | Property tax exemption |
| Florida | None | Full retail (most) | No sales tax |
| New York | $0.20/W rebate | Full retail | Property tax exemption |
| Massachusetts | None | Net metering | SREC market ($200-300/MWh) |
| New Jersey | None | Full retail | SREC market |
| Colorado | Varies by utility | Full retail | Property tax exemption |
| Maryland | $1,000 grant | Full retail | SREC market |
Net Metering Status by State:
| Policy Type | States | Value to Homeowner |
|---|---|---|
| Full retail net metering | 28 states | Excellent |
| Reduced rate (avoided cost) | 10 states | Good |
| Net billing (lower export rate) | 7 states | Fair |
| No statewide policy | 5 states | Varies |
California NEM 3.0 Impact:
California's new rules (April 2023) reduced export values by ~75%. Key changes:
- Export credits based on "avoided cost" (
$0.05/kWh) instead of retail ($0.30/kWh) - Makes battery storage essential for ROI
- 9-year payback periods are now common (vs. 6 years under NEM 2.0)
SREC Markets (Solar Renewable Energy Credits):
| State | SREC Value | Annual Value (8 kW) |
|---|---|---|
| Massachusetts | $200-300/MWh | $2,400-3,600 |
| New Jersey | $150-200/MWh | $1,800-2,400 |
| Maryland | $60-80/MWh | $720-960 |
| Pennsylvania | $30-50/MWh | $360-600 |
| Ohio | $10-20/MWh | $120-240 |
Battery Storage Integration
Home Battery Options (2026):
| Battery | Capacity | Power | Cost Installed | Warranty |
|---|---|---|---|---|
| Tesla Powerwall 3 | 13.5 kWh | 11.5 kW | $11,500 | 10 years |
| Enphase IQ 5P | 5 kWh | 3.84 kW | $6,000 | 15 years |
| LG Chem RESU | 16 kWh | 7 kW | $12,000 | 10 years |
| Generac PWRcell | 9-18 kWh | 4.5-9 kW | $10,000-18,000 | 10 years |
| Sonnen | 10-20 kWh | 4.8-8 kW | $15,000-30,000 | 15 years |
| FranklinWH | 13.6 kWh | 10 kW | $13,500 | 12 years |
When Batteries Make Sense:
| Situation | Battery Value | ROI Factor |
|---|---|---|
| Time-of-use rates | High | Charge cheap, use expensive |
| Frequent outages | High | Backup power value |
| NEM 3.0 states | Essential | Maximize self-consumption |
| Net metering states | Low | Grid is your battery |
| Off-grid | Essential | Only option |
| Demand charges | High | Peak shaving |
Whole-Home Backup Requirements:
| Coverage Level | Battery Size | Duration (Avg Home) |
|---|---|---|
| Essentials only | 10 kWh | 8-12 hours |
| Most loads | 20 kWh | 12-18 hours |
| Whole home | 30-40 kWh | 18-24 hours |
| Extended outage | 40+ kWh | 24+ hours |
Battery Economics (2026):
Without the federal tax credit for residential batteries:
- Battery-only installs no longer receive tax benefits
- Add $6,000-18,000 to solar project cost
- Payback depends heavily on TOU rates and outage frequency
- California/Hawaii: Often necessary for ROI
- Net metering states: Harder to justify financially
Installation Process and Timeline
Typical Solar Installation Timeline:
| Phase | Duration | What Happens |
|---|---|---|
| Site assessment | 1-2 hours | Roof inspection, electrical evaluation |
| Design & proposal | 3-7 days | System sizing, layout, pricing |
| Contract signing | Same day | Lock in pricing, terms |
| Permitting | 2-8 weeks | Varies wildly by jurisdiction |
| Equipment delivery | 1-2 weeks | Panels, inverters, racking |
| Installation | 1-3 days | Mount panels, wire system |
| Inspection | 1-2 weeks | City/county electrical inspection |
| Utility approval | 1-4 weeks | PTO (Permission to Operate) |
| Total | 6-16 weeks | Faster in solar-friendly areas |
Roof Requirements:
| Factor | Ideal | Acceptable | Problematic |
|---|---|---|---|
| Age | <10 years | 10-20 years | >20 years (replace first) |
| Material | Composite shingle, metal | Tile, flat roof | Wood shake, slate |
| Pitch | 15-40 degrees | 0-15 or 40-50 | >50 degrees |
| Orientation | South | East/West | North (usually no) |
| Shading | <5% annual | 5-15% | >15% (use microinverters) |
| Condition | Excellent | Good | Poor (repair first) |
Installation Day Expectations:
| Time | Activity |
|---|---|
| 8:00 AM | Crew arrives, safety setup |
| 8:30 AM | Racking/mounting installed |
| 12:00 PM | Panels mounted |
| 2:00 PM | Wiring completed |
| 4:00 PM | Inverter/electrical connected |
| 5:00 PM | System test, cleanup |
DIY Solar Considerations:
- Permits: Most jurisdictions require licensed electrician signoff
- Safety: Rooftop work and electrical are high-risk
- Warranty: DIY installation voids many manufacturer warranties
- Savings: ~30-40% cost reduction vs. professional install
- Recommendation: Only for experienced electricians/roofers
Pro Tips
- 💡Get at least 3-5 quotes from different installers—prices vary 20-30% for identical systems.
- 💡Check your roof condition first; if replacement is needed within 10 years, do it before installing solar.
- 💡Size your system for future needs (EVs, heat pumps) since adding panels later is less cost-effective.
- 💡South-facing roofs are ideal, but east-west installations still produce 80-90% of optimal output.
- 💡Use microinverters or optimizers if you have any shading—they prevent one shaded panel from reducing entire system output.
- 💡Compare cash purchase, solar loans, leases, and PPAs—2026 economics may favor leasing without the tax credit.
- 💡Verify your utility's net metering policy before installation—it determines how excess production is valued.
- 💡Check state SREC programs (Massachusetts, New Jersey, Maryland) for additional income from your system.
- 💡Request production guarantees in writing—reputable installers guarantee specific annual kWh output.
- 💡Consider timing: wait for potential new federal incentives, or lock in current state programs before they change.
- 💡Battery storage is essential in California (NEM 3.0) but optional elsewhere—evaluate based on your specific situation.
- 💡Keep all documentation for tax purposes—the commercial credit via leases may have additional requirements.
Frequently Asked Questions
The average US home using 900 kWh/month needs 15-20 panels (400W each) for an 8 kW system that offsets most usage. The exact number depends on: your monthly electricity consumption, local sun exposure (Southwest needs fewer panels than Northeast), panel wattage (400W standard, 450W premium), and available roof space. Use your utility bill to calculate precisely.
