Chapter 27: Solar and Battery Systems

Solar power and battery storage are the highest-value, longest-investment electrical projects most homeowners will consider. They're also the projects with the most code complexity, the strongest case for professional installation, and the largest variation in quality between installers.

This chapter is more conceptual than step-by-step. The work itself is genuinely a professional project for almost everyone. What we'll cover here is what you need to know to be an informed customer, evaluate proposals, and understand what's being installed in your home.

Estimated time: 2–5 days for professional installation. Cost: $15,000–50,000+ for solar; $10,000–25,000 for battery; verify any current incentives before including them in your budget. Permit required: yes, with multiple inspections and utility interconnection requirements.

Solar System Components

A residential solar system consists of:

Solar panels (PV modules). The visible part. Convert sunlight to DC electricity. Modern residential panels are typically 350–450W each, in 60–72 cell configurations.

Inverters. Convert DC from panels to AC for use in the house. Two main approaches:

• String inverters: one large inverter for the whole array. Cheaper, but if shaded, the whole string under-performs.
• Microinverters: small inverter per panel. More expensive, but each panel performs independently. Better for homes with partial shading.

Some systems use power optimizers with a string inverter as a middle-ground.

Mounting hardware. The racking that holds panels to the roof (or to a ground-mount structure). Specific to roof type (asphalt shingle, tile, metal, etc.).

DC and AC disconnects. Required by code for emergency shutoff. The "Rapid Shutdown" capability (NEC 690.12) is required for new residential PV systems.

Net meter or bidirectional meter. Replaces (or supplements) the standard utility meter. Measures both consumption and back-feed to the grid.

Combiner box / junction box. Where DC strings combine before reaching the inverter.

For a typical 8 kW residential system: 20–25 panels, mounting hardware, microinverters or string inverter+optimizers, AC and DC disconnects, monitoring equipment, and interconnection components.

Battery Storage Components

A residential battery system adds:

Battery modules. The actual storage. Common chemistries:

Common residential capacities: 10 kWh, 13.5 kWh, 20 kWh, or scalable systems.

Battery inverter / hybrid inverter. Converts between battery DC and AC for the house. Some systems combine solar and battery in one "hybrid inverter."

Backup interface (gateway / interconnect). Manages the home's electrical system during outages, separating critical loads from non-critical, coordinating between solar, battery, and grid.

Critical loads panel. A sub-panel containing only the circuits that should run during outages (refrigerator, lights, some outlets, possibly HVAC). Non-critical loads stay on the main panel and don't draw from the battery during outages.

Choosing a Solar Installer

For most homeowners, this is the most important decision in the project.

Things to verify:

• North American Board of Certified Energy Practitioners (NABCEP) certification for at least the lead installer
• Oklahoma electrical contractor license
• Manufacturer certifications for the equipment they're installing
• Insurance (general liability, workers' comp)
• Bond if working in jurisdictions that require it
• Years in business (look for 5+ years; many fly-by-night solar companies appear and disappear)

Get multiple bids. 3–5 is typical for solar. Compare:

• System size (kW DC and kW AC)
• Number and brand of panels
• Inverter type and brand
• Production estimate (annual kWh)
• Total cost before and after incentives
• Warranty terms (panels: 25 years; inverters: 10–12 years for string, 25 years for microinverter; workmanship: 10+ years from installer)
• Monitoring system included or extra
• Battery option (price separately)

Watch for red flags:

• Pressure tactics ("price expires in 24 hours")
• Unrealistic production claims
• "Free solar" offers (these are usually leases or PPAs that may save money but transfer ownership)
• Lack of detailed proposal

Lease vs purchase vs PPA:

• Outright purchase (cash or financed): you own the system. Compare financing and ownership costs, and verify any claimed tax benefits for your situation.
• Lease: you pay a fixed monthly amount; the leasing company owns the panels.
• Power Purchase Agreement (PPA): you pay for the power produced; the company owns the panels.

For most homeowners, outright purchase (cash or solar-specific loan) provides the best long-term value. Leases and PPAs are simpler but the savings are smaller.

Federal And State Incentives

Federal Residential Clean Energy Credit (Section 25D): This credit is not available for expenditures made after December 31, 2025, including residential solar and qualifying battery storage. Do not subtract a 30% homeowner credit when budgeting a new installation in 2026.

For this credit, an expenditure is generally treated as made when the original installation is completed. Paying before the deadline does not qualify an installation completed afterward. For construction or reconstruction, the timing rule is when the taxpayer first uses the completed structure.

Checked September 27, 2026: IRS Guidance On The Section 25D Deadline. If you are claiming eligible earlier expenditures, confirm the requirements for your tax year with a qualified tax professional.

State, local, and utility programs: Check current eligibility and written program terms before including any rebate or incentive in your budget.

Utility export credits: Ask your utility for its current interconnection requirements, export-credit rates, fees, and settlement rules. Use those terms when estimating savings.

Sizing the System

System size depends on:

• Annual electricity usage (in kWh; check your utility bills for the past 12 months)
• Roof orientation and shading
• Available roof area
• Goals (offset 50% of usage? 100%? More?)

A typical OKC home using 1,000 kWh/month:

• 100% offset target: about 8 kW DC system, 20–24 panels
• Roof area required: about 500–600 sq ft of unshaded south-facing roof

If your roof is unshaded south-facing, sizing is straightforward. If your roof has complications (shading, multiple orientations, complex shapes), sizing requires expertise.

Don't oversize. The marginal panel beyond what offsets your usage is much less valuable (if net metering pays full retail) or has minimal value (if net metering pays wholesale).

Battery Sizing

Battery size depends on goals:

• Whole-home backup during outages: match battery capacity to expected outage duration and home's daily load. For a typical OKC home (30 kWh/day), 13–30 kWh of battery covers 12–24 hours.
• Critical loads only during outages: smaller battery sufficient. 10–13 kWh handles refrigerator, some lights, internet, and HVAC for 12–24 hours.
• Self-consumption (no outage backup): size battery to store excess solar production for evening use. Often 10–20 kWh.
• Time-of-use rate optimization: size to shift consumption from peak to off-peak hours. Smaller battery may be sufficient.

For most homeowners interested in battery storage, the primary motivation is outage resilience. OKC's weather makes this a real value. A 13–20 kWh battery is the practical target for most homes.

The Installation Process

A typical solar+battery install:

Day 0–30: Design and engineering.

• Initial consultation, site visit, roof inspection
• System design and proposal
• Contract signing
• Permit application
• Utility interconnection application

Day 30–90: Permitting and ordering.

• Permit approval (varies by jurisdiction)
• Equipment ordering
• Sometimes structural engineering review

Day 90–120: Installation.

• 1–3 days for solar mounting and wiring
• Additional 1–2 days for battery installation
• Inverter, monitoring, and disconnect installation

Day 120–150: Inspection and interconnection.

• Local building inspector visit
• Utility interconnection inspection
• Permission to operate (PTO) granted by utility
• System turned on

Total timeline: 3–5 months for solar; 4–6 months for solar+battery.

Interconnection: How Solar Talks to the Grid

Net-metered solar systems are "grid-tied": they feed excess production back to the utility, drawing from the utility when production is insufficient.

The interconnection agreement is a contract between you and the utility specifying:

• The size of your system
• How excess production is credited
• Safety requirements (anti-islanding, automatic disconnect during grid outages)
• Inspection and approval requirements

Most utilities require:

• A bidirectional meter (replaces standard meter)
• Compliant inverter with anti-islanding protection
• Visible disconnect switch accessible to utility workers

The utility approval process typically adds 2–4 weeks to the project timeline. Your installer handles the paperwork.

Battery Backup Modes

Battery systems can operate in several modes:

Self-consumption (no backup): battery charges from solar during the day, discharges in the evening. Reduces grid imports. Doesn't help during outages.

Backup-ready: battery is held at high charge, ready for outage. Day-to-day, it self-consumes only minimally.

Time-of-use optimization: battery charges when rates are low, discharges when rates are high.

Off-grid: the system operates independently of the utility. Requires very large battery and additional equipment. Rare for typical residential.

Most residential systems operate in a hybrid mode that prioritizes self-consumption while maintaining a reserve for outage backup.

Costs And Payback

Use current, itemized installer quotes to compare solar, battery storage, and combined systems. A useful estimate separates equipment, installation, roof or electrical upgrades, financing, and ongoing maintenance. Do not assume a federal Section 25D credit for a new 2026 installation.

Ask each installer to explain the assumptions behind projected savings:

• Your electricity use and current utility rates
• Expected production for your roof's orientation and shading
• Your utility's export-credit rates, fees, and settlement rules
• Only incentives whose current eligibility you have verified
• Financing costs, maintenance, and future equipment replacement

Payback varies by home and system. Compare projected savings with the full ownership cost, and ask how the estimate changes if production or electricity rates differ from the forecast. Battery storage can provide outage backup; evaluate that value separately from bill savings.

Long-Term Considerations

A few things to think about:

Roof replacement. Solar panels typically last 25+ years. Asphalt shingle roofs typically last 20–25 years. If your roof is older than 10 years, consider replacing it BEFORE solar installation. Otherwise, you'll be removing and reinstalling panels in 10–15 years to replace the roof, adding $3,000–5,000 to the cost.

Inverter replacement. String inverters typically last 10–15 years. Microinverters typically last 25 years. Plan for inverter replacement at some point.

Battery replacement. Lithium batteries degrade. Most warranties guarantee 70–80% capacity at 10 years. Plan for battery replacement around year 15–20.

Selling the home. Studies show solar adds value to home sales, but the value depends on whether the system is owned (yes) or leased (often no, and can complicate sales).

Future expansion. Modern systems are often modular. You can add panels or battery capacity later if needs change.

Common Mistakes (Working with Installers)

Choosing solely on price. The cheapest installer is often the cheapest for a reason. Quality of materials, installation, and warranty support varies dramatically.

Not understanding the warranty. "25-year warranty" might cover only the panel itself, not the labor to replace it. Read the fine print.

Believing optimistic production estimates. Some installers use idealized models. Get realistic estimates based on your specific roof's shading and orientation.

Skipping the home assessment. A reputable installer will visit your home, inspect the roof and panel, and design a system specific to your situation. Beware of "online quotes" without site visits.

Ignoring the financing terms. Solar loans vary widely in interest rates and terms. A high-interest "solar loan" can wipe out savings.

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