Question 1

What is the 20% rule for solar panels?

Accepted Answer

The 20% rule is a general guideline that says your solar system should be sized to offset about 80-100% of your electricity usage, not exceed it by more than 20%. Many utilities won't allow systems significantly larger than your historical usage, and they may not pay you well for excess production. This rule helps ensure you get the best return on investment and avoid installing more capacity then you actually need.

Question 2

Is 7 kW enough to run a house?

Accepted Answer

A 7 kW solar system can power most average-sized homes that use around 800-1,000 kWh per month. In sunny climates, a 7 kW system produces roughly 9,000-11,000 kWh annually. However, homes with electric heating, pools, or EV charging may need larger systems. The best approach is to review 12 months of electricity bills to determine actual usage before sizing a system.

Question 3

What should be on a solar installation invoice?

Accepted Answer

A complete solar invoice should include your business name and contractor license, client details, property address, system specifications (total kW, panel count, inverter model), itemized equipment costs, installation labor hours, permit and inspection fees, any roof work or electrical upgrades, subtotal, applicable taxes, total due, payment terms, and warranty information. Include your NABCEP certification if you have one.

Question 4

How do I bill for solar panel installation?

Accepted Answer

Most solar installers use milestone billing for larger projects: a deposit (10-25%) to order equipment, a payment (30-40%) when equipment arrives on site, another payment (25-30%) after installation is complete, and final payment (10-20%) after inspection and utility approval. For smaller residential jobs, some installers bill 50% deposit and 50% on completion. Always document payment schedules in your contract.

Question 5

Should I include equipment serial numbers on solar invoices?

Accepted Answer

Yes, including panel and inverter serial numbers is good practice. It creates a permanent record for warranty claims, helps with insurance documentation, and is often required for rebate applications. Many installers attach a separate equipment schedule document with all serial numbers and reference it on the main invoice.

Question 6

Can I customize this solar invoice template?

Accepted Answer

Absolutely. Add your company logo, adjust line items for your typical installations, include fields for system production guarantees, and modify the layout to fit your workflow. The Excel and Word versions are especially easy to customize with your branding and preferred format.

Question 7

How do I document tax credits on a solar invoice?

Accepted Answer

While you don't calculate the federal tax credit for customers, it's helpful to note on the invoice that the system may qualify for the 30% federal solar tax credit (ITC). Include the total system cost clearly so homeowners can reference it when filing taxes. Some states have additional incentives, so mention those too. Avoid promising specific credit amounts since eligibility depends on the customer's tax situation.

Question 8

What warranty information should be on a solar invoice?

Accepted Answer

Include warranty details for all major components: panel manufacturer warranty (typically 25 years for production, 10-12 years for product defects), inverter warranty (usually 10-25 years depending on brand), and your workmanship warranty (commonly 5-10 years). Note the start date of each warranty and keep records of serial numbers. This protects both you and the homeowner if issues arise later.

Question 9

Do commercial solar invoices require different information?

Accepted Answer

Commercial solar projects often require additional documentation: your federal tax ID (EIN), detailed equipment schedules, prevailing wage compliance if applicable, lien waiver forms, proof of insurance with higher coverage limits, and sometimes AIA-format billing for progress payments. Larger commercial jobs may also need certified payroll records and bonds. Check with the property owner or general contractor for their specific requirements.

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What to Include in Your Solar Invoice

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