Residential Battery Storage Reference
Why this reference exists
Residential battery storage went from a steep premium add-on to a mainstream install while the IRA 25D 30 percent credit (no cap) cut the effective price by roughly a third. That credit was terminated for expenditures after December 31, 2025, so current pricing runs on gross cost plus state and utility programs, and the payback conversation is harder than it was. Use cases are unchanged: outage backup, solar self-consumption, time-of-use arbitrage, demand-response participation. Installer revenue per install is a solid multiple of the labor and margin on a typical service call, at 15-25 percent gross margin.
Common products
Tesla Powerwall 3: 13.5 kWh, integrated inverter, 11.5 kW continuous + 17 kW surge. Mid-teens-to-high-teens (thousands) installed. Stacks up to 4 units. Strong app + ecosystem.
Enphase IQ Battery 5P / 10C: 5 + 10 kWh modular. Microinverter-based (each battery has own inverter). Low-teens to low-twenties (thousands) installed depending on configuration. Strong for systems already on Enphase microinverters.
LG Resu 16H Prime: 16 kWh, high-voltage DC. Pairs with hybrid inverter (Sol-Ark, SolarEdge). Mid-teens-to-high-teens (thousands) installed.
FranklinWH aPower: 13.6 kWh, integrated inverter. Comparable to the Powerwall's range installed. Strong native generator integration.
Generac PWRcell: 9-18 kWh modular. Pairs with PWRcell inverter. Similar range, trending toward the higher end for larger configurations installed. Strong for whole-home backup with existing Generac generator.
SimpliPhi PHI / Briggs & Stratton: emerging modular options.
Sizing approach
Customer goals determine sizing:
Outage backup only:
- Calculate critical loads (fridge, freezer, well pump, furnace fan, lighting, internet)
- 5-10 kWh covers most homes 12-24 hours
- 13.5 kWh (Powerwall) covers 24-48 hours
Whole-home backup:
- 20-30 kWh typical
- Pair with generator for extended outages
- Or 3+ Powerwalls
Solar self-consumption (no outage focus):
- Daily solar surplus / 1.5 = battery size
- 10-15 kWh typical with 8-12 kW solar
Time-of-use arbitrage (markets with TOU rates):
- Off-peak charge → peak discharge
- 10-13 kWh typical
- Net savings: modest annual amount, scaling with the local peak-to-off-peak rate spread
Installation requirements
Site assessment:
- Garage, utility room, or basement install (battery + inverter)
- 12-24" wall clearance per manufacturer
- Outdoor install requires weather-rated enclosure (some products)
- Local temperature: most batteries 32-104°F range; consider conditioned space
- Floor load: battery 200-350 lbs typical; verify floor framing
Electrical work:
- Sub-panel for backed-up critical loads (usually)
- Main panel breaker interconnect (per local code)
- 240V dedicated circuit
- Grounding + bonding
- Permit always
For solar pairing:
- AC-coupled: battery has inverter; ties to solar AC output
- DC-coupled: battery shares inverter with solar; higher efficiency, requires hybrid inverter
- Retrofit: AC-coupled typical
- New build: DC-coupled often better
Code + permitting
Battery installs require permits + inspection:
- NEC 706 Energy Storage Systems (introduced 2017, expanded 2020 + 2023)
- UL 9540 + 9540A (battery safety + fire propagation testing)
- Local AHJ may require fire-marshal review
- Building code clearances + ventilation per manufacturer + NEC
- Some jurisdictions cap battery capacity per dwelling (typical 40 kWh limit; some 80 kWh)
Permit cost is a small fraction of the overall install budget.
Utility interconnection agreement required if battery interacts with grid (most do). Some utilities charge a modest interconnection fee.
IRA tax credit + incentives
Federal 25D (Residential Clean Energy Credit) - TERMINATED for expenditures after December 31, 2025:
- Was 30% of total cost (battery + install + permits), no cap
- Battery 3 kWh+ qualified (added 2023); standalone battery qualified, solar pairing not required
- Unused credit carried forward if tax owed was insufficient
- Do not quote this on new work. It only applies to expenditures made on or before December 31, 2025
State incentives (variable):
- California SGIP (Self-Generation Incentive Program): a meaningful per-kWh equity incentive
- New York NY-Sun + NYSERDA: battery rebates available
- Massachusetts Connected Solutions: per-kWh discharge incentive
- Maryland Residential Clean Energy Rebate
- Many utility-administered demand-response participation rebates
With 25D gone, the stack is state plus utility only. Coverage varies widely by market; price the job off gross cost and treat every incentive as a deduction you have confirmed is still funded.
Operating modes
Backup-only: battery sits at full charge; discharges only during outage.
- Pro: long battery life (less cycling)
- Con: no daily savings
Self-consumption: solar charges battery during the day; battery discharges in the evening.
- Pro: maximize solar value
- Con: daily cycling reduces battery life vs backup-only
Time-of-use: grid charges battery at off-peak; battery discharges at peak.
- Pro: arbitrage savings
Demand response: utility can call on battery during grid peak.
- Pro: utility pays customer a per-event incentive for participation
- Con: less control during demand events
Most modern systems combine modes. App or installer configures the priority.
Common pitfalls
- Undersized for goal: customer wants whole-home backup, gets 5 kWh; furious during first outage
- Wrong inverter pairing: battery + solar inverter incompatibility
- No sub-panel for critical loads: backup mode powers entire house at outage = battery dead in 4 hours
- Heat in install location: battery derate or shutdown
- Forgetting AHJ permit: utility refuses interconnection
- Not configuring time-of-use: customer paid for arbitrage feature but never enabled
- Customer expectations: "the battery powers my AC for a week" - sizing mismatch
- Generator + battery uncoordinated: both fire; both cycle inefficiently
Maintenance + lifespan
Lithium iron phosphate (LFP) batteries (Tesla, Enphase, FranklinWH 2024+): 6,000+ cycles, 10-15 year life, less fire risk than NMC.
NMC (older Tesla, LG Chem, some Enphase): 4,000-6,000 cycles, 8-12 year life.
Typical residential cycle: 0.5-1 per day. 10-year cycle count: 1,800-3,650. Both chemistries handle this.
Warranty: most manufacturers offer 10-year + 70-80% capacity guarantee.
Service: annual visual + log review. Most issues self-diagnose via app. Failed cell = manufacturer replacement under warranty.
Customer talking points
The conversation that closes:
- "Outage backup: keeps your essentials running 24-48 hours."
- "State rebate and utility program, if your market has them - the 30 percent federal credit ended after 2025."
- "Here is the gross cost, and here is what the confirmed incentives take off it."
- "Pairs with your solar (if you have it) or works standalone."
- "App on your phone shows battery state + lets you control modes."
- "10-year warranty + ~15 year typical life."
Outage frequency in customer's area drives urgency. Customers in PSPS (California Public Safety Power Shutoff) zones close at 60%+ rate. Customers with no outage memory close at 15-25%.
The single sentence that closes battery storage names only live incentives: "After your state rebate and utility program, you'd pay about $X, and the battery pays itself back through outage protection and bill savings." The 30 percent federal credit ended after 2025, so quoting it now produces a customer who finds out at tax time. Show the math: gross cost, minus credits, minus utility rebates, minus annual savings. Most customers haven't seen the full incentive stack laid out + dramatically underestimate the actual cost.
References
- NEC Article 706 Energy Storage Systems
- UL 9540 + 9540A Battery Safety Standards
- IRS Form 5695 (25D credit)
- DOE Better Buildings Residential Energy Storage
- California Self-Generation Incentive Program
- Manufacturer specs (Tesla, Enphase, LG, FranklinWH, Generac)
- Manuall internal: IRA Home Energy Tax Credits: What Ended, What Survives, and What You Can Still Quote, Electrical Panel Upgrades for Electrification Reference