Solar Installation Estimate Guide for Contractors (2026)

Solar installation is booming. The 30% federal ITC (Investment Tax Credit) through 2032, rising utility rates, and growing consumer demand mean more jobs than ever — but also more competition. The contractors who win aren't the cheapest. They're the ones who deliver professional proposals fastest.

This guide covers everything you need to estimate solar projects accurately and profitably.

System Sizing Fundamentals

Before you can estimate, you need to size the system. Every solar estimate starts with:

• Annual electricity usage: Pull from the customer's utility bill. Average US home uses 10,500 kWh/year. Texas averages 14,000+ kWh/year (thanks, AC).
• Target offset: Most customers want 80-100% offset. Design for 90% to account for degradation over 25 years.
• Sun hours: San Antonio averages 5.3 peak sun hours/day. Phoenix is 6.5, Seattle is 3.8. Use PVWatts or your design software for accurate local data.
• System size formula: Annual kWh ÷ (365 × peak sun hours × 0.8 efficiency) = kW needed. A 14,000 kWh home in SA needs roughly 9-10 kW.
• Panel count: System kW ÷ panel wattage. A 10 kW system with 400W panels = 25 panels.

Equipment Costs (2026 Pricing)

Solar Panels

• Budget tier (Hanwha Q Cells, Canadian Solar, Trina): $0.25–$0.35/W ($100–$140 per 400W panel)
• Mid tier (REC, LONGi, Silfab): $0.35–$0.50/W ($140–$200 per panel)
• Premium tier (LG, SunPower/Maxeon, Panasonic): $0.50–$0.80/W ($200–$320 per panel)

For a 10 kW system: $2,500–$8,000 in panel costs depending on tier. Most residential installers use mid-tier for the best margin-to-warranty ratio.

Inverters

• String inverter (SolarEdge, Fronius): $1,000–$2,500 for residential. Cheapest option but single point of failure.
• Microinverters (Enphase IQ8+): $150–$200 per panel. Panel-level optimization, better for shading. Most popular for residential.
• Power optimizers + string inverter (SolarEdge): $2,000–$3,500 total. Hybrid approach. Good for complex roofs.

For 10 kW with Enphase microinverters: ~$4,000–$5,000. With SolarEdge string + optimizers: ~$3,000–$3,500.

Racking & Mounting

• Roof mount (IronRidge, Unirac): $0.10–$0.15/W ($1,000–$1,500 for 10 kW)
• Ground mount: $0.20–$0.40/W ($2,000–$4,000 for 10 kW). Requires concrete footings or ground screws.
• Tile roof adapters: Add $0.05–$0.10/W for tile hook adapters (common in TX)

Battery Storage (Optional Upsell)

• Tesla Powerwall 3: $8,500–$12,000 installed
• Enphase IQ Battery 5P: $6,000–$9,000 installed
• Franklin WH (whole home): $10,000–$15,000 installed

Batteries add 30-50% to project value with strong margins. Always present as an option — even if the customer doesn't buy now, you've planted the seed for a future sale.

BOS (Balance of System)

• Wiring, conduit, disconnects, breakers: $500–$1,500
• Monitoring system: Usually included with inverter (Enphase Enlighten, SolarEdge app)
• Roof penetration sealant & flashing: $200–$500
• Production meter (if required): $100–$300

Labor Costs

A typical residential install (8-12 kW roof mount) takes a 3-4 person crew 1-2 days:

• Crew labor (3-4 installers × 8-16 hrs): $2,000–$4,000
• Electrician (panel upgrade, interconnection): $500–$1,500
• Project management / design: $500–$1,000
• Site survey: $0–$300 (many companies absorb this as sales cost)

Soft Costs (Don't Forget These)

• Permitting: $200–$1,000 depending on city/county
• Engineering / PE stamp: $200–$500 (required for permit in most jurisdictions)
• Utility interconnection application: $0–$500
• HOA approval: Free but time-consuming. Texas Solar Rights Act (§171.007) limits what HOAs can restrict.
• Sales commission: $500–$2,000 per deal (if you have a sales team)
• Customer acquisition cost: $0.20–$0.50/W industry average

Complete Solar Estimate Example

10 kW residential rooftop system in San Antonio — composition shingle roof, 200A panel, no battery:

Pricing Strategies & Margins

• Price per watt: The industry standard unit. Residential installs in 2026 range $2.00–$3.50/W before ITC. Under $2.00/W you're leaving money on the table. Over $3.50/W you're losing to competition (unless it's premium panels + battery).
• Net margins: Top solar companies run 15-25% net profit. New companies often underprice at 8-12% trying to win market share — dangerous because one roof issue or warranty claim wipes the profit.
• Battery attach rate: Industry average is 25-30%. If you're below that, you're not presenting batteries well. Every battery adds $3,000–$6,000 in profit.
• Financing markup: If you offer dealer fees to loan companies (Sunlight, GoodLeap, Mosaic), factor 15-25% dealer fee into your price. The customer's monthly payment is what they care about, not the gross price.

What to Include in Every Solar Proposal

1. 1. System design overview — kW size, panel count, inverter type, estimated production (kWh/year)
2. 2. Equipment specifications — panel model, inverter model, warranty terms (25-year panel, 25-year inverter for Enphase)
3. 3. Itemized pricing — equipment, labor, permits, BOS. Transparency builds trust.
4. 4. Incentive breakdown — 30% ITC, any state/local rebates, SREC value if applicable
5. 5. Savings projection — Year 1 savings, payback period, 25-year cumulative savings. Use current utility rates + 3% annual escalator.
6. 6. Project timeline — Site survey → design → permit → install → inspection → PTO (Permission to Operate). Typical: 4-8 weeks.
7. 7. Warranty summary — Workmanship warranty (10 years), panel warranty (25 years), inverter warranty (25 years), roof penetration warranty

Common Mistakes in Solar Estimating

1. 1. Not checking roof condition. If the roof needs replacement in 5 years, you'll be back to remove and reinstall panels (at your cost if under workmanship warranty). Always inspect the roof — or partner with a roofer.
2. 2. Ignoring shading. A tree that shades 3 panels kills system performance. Use satellite imagery or on-site shade analysis. Don't oversell production.
3. 3. Underestimating permit timelines. Some TX cities take 4-6 weeks for solar permits. Set expectations upfront.
4. 4. Quoting without seeing the electrical panel. A required 200A upgrade changes the price by $2,000+. Always check.
5. 5. Not accounting for roof type. Tile roofs cost 30-50% more to install on than composition shingle. Metal roofs need different clamps. Flat roofs need tilt racking.

Create Solar Proposals in Minutes

Solar proposals are complex — equipment specs, incentive calculations, savings projections, and financing options. Building one from scratch takes hours and leaves room for errors that cost you deals.

BidForge lets solar contractors describe the project, input system specs, and generate a professional branded proposal in minutes. Complete with itemized pricing, your company branding, and a shareable link for the homeowner.