Home Solar Power Systems: Complete 2025–2030 Guide with Cost, ROI & Innovation

                   
2024-12-26 | Home Solar Power Systemshuijue groupResidential SolarSmart Home EnergySolar Battery Storagesolar ROIV2H TechnologyVirtual Power Plant

The global residential solar market reached 147.98 GW of installed capacity in 2025, projected to grow to 204.56 GW by 2030. With solar panel costs dropping below $0.30/watt and battery storage becoming mainstream, home solar power systems have evolved from an eco-friendly luxury to a strategic financial asset. This guide covers everything from cost breakdown and ROI analysis to cutting-edge innovations like Virtual Power Plants (VPP), Vehicle-to-Home (V2H) technology, and AI-driven energy management — helping you make an informed decision for your home’s energy future.

For homeowners seeking integrated container energy storage solutions that scale from residential to commercial applications, understanding the full landscape of home solar technology is the first step toward energy independence.

📊 Quick Answer: Home Solar Power Systems at a Glance (2025–2030)

Metric 2025 2030 (Projected) Trend
Global residential solar capacity 147.98 GW 204.56 GW ↑ 38% growth
Solar panel cost per watt $0.28–$0.35 $0.18–$0.22 ↓ 35% decline
Average 6kW system cost (US) $16,800 $12,000 ↓ 29% decline
Typical payback period 6–9 years 4–6 years ↓ 33% shorter
Home battery adoption rate 18% 45% ↑ 150% growth
VPP capacity (global) 12 GW 80–160 GW ↑ 10× growth
V2H market size $1.19B $3.2B ↑ 169% growth

1. Why Home Solar Power Systems Are Reshaping Residential Energy

Home solar power systems convert sunlight into electricity using photovoltaic (PV) panels, providing households with clean, renewable energy. In 2025, the world added a record 698 GW of new solar PV capacity, bringing the global total to 2,383 GW — a 59-fold increase from just 40 GW in 2010. Residential installations account for a growing share of this expansion.

Several converging forces are driving residential solar adoption:

Driver 2025 Status Impact on Homeowners
Electricity price inflation Global avg +4.2% annually Solar locks in fixed generation cost
Solar panel cost decline $0.28–$0.35/W (down from $4/W in 2008) System payback in 6–9 years
Government incentives 30% US ITC, EU grants, Asian subsidies Reduces upfront cost by 20–40%
Grid reliability concerns Outages increasing in frequency Solar+storage provides backup power
Climate commitments 120+ countries with net-zero targets Policy tailwinds accelerate adoption
EV adoption synergy 17M+ EVs globally in 2025 Solar charges EVs at near-zero cost

The shift is not just about generating clean electricity — it’s about redefining how homes interact with the energy grid. Modern home solar power systems increasingly include battery storage, smart inverters, and software platforms that enable households to optimize self-consumption, participate in grid services, and even earn revenue from excess energy.

2. Environmental Impact & Carbon Reduction

One of the most compelling reasons homeowners choose solar is the significant environmental benefit. A typical 6 kW residential solar system offsets approximately 7,000–8,000 lbs of CO₂ annually, equivalent to planting 80 trees or taking one car off the road.

Environmental Metric Grid Electricity Home Solar (6kW) Solar + Storage
Annual CO₂ emissions (lbs) 8,500–12,000 600–900 200–400
20-year CO₂ offset (tons) 0 70–80 80–90
Water consumption (gal/year) 3,000–5,000 ~0 ~0
NOx emissions (lbs/year) 15–25 0 0
SO₂ emissions (lbs/year) 20–35 0 0
Particulate matter (lbs/year) 2–4 0 0
Land use efficiency Moderate Rooftop (no extra land) Rooftop (no extra land)

Regional Carbon Impact Comparison

Region Grid Carbon Intensity (gCO₂/kWh) 6kW Solar Annual Offset (tons CO₂) Equivalent Trees Planted
Poland 640 9.2 425
Australia 520 7.5 345
USA (avg) 385 5.5 255
Germany 340 4.9 225
Japan 460 6.6 305
France 85 1.2 55
Norway 30 0.4 20

Even in regions with relatively clean grids like France and Norway, home solar systems reduce reliance on imported energy and provide grid resilience benefits. In coal-heavy grids like Poland or Australia, the carbon offset is dramatic — a single 6 kW system in Poland saves as much CO₂ as planting 425 trees every year.

3. The True Economics: Cost Breakdown & ROI Analysis

Understanding the real cost of home solar power systems requires looking beyond the sticker price. A complete cost analysis includes upfront investment, available incentives, ongoing maintenance, and long-term energy savings.

System Cost by Size (2025 Average US Prices)

System Size Suitable For Cost Before Incentives After 30% Tax Credit Annual Savings Payback Period
3 kW Small apartment / 1-2 people $8,400 $5,880 $650–$900 6.5–9 years
5 kW Medium home / 3-4 people $14,000 $9,800 $1,100–$1,500 6.5–9 years
6 kW Standard family home $16,800 $11,760 $1,300–$1,800 6.5–9 years
8 kW Large home / EV charging $22,400 $15,680 $1,800–$2,400 6.5–8 years
10 kW Very large home / multiple EVs $28,000 $19,600 $2,200–$3,000 6.5–8 years
15 kW Small business / farmhouse $42,000 $29,400 $3,300–$4,500 6.5–8 years

Cost Component Breakdown (6 kW System)

Component Cost % of Total Notes
Solar panels (16–20 panels) $4,200 25% $0.25–$0.30/W
Inverter (string or microinverter) $1,800–$3,200 15–19% Microinverters cost more
Mounting & racking $1,400 8% Roof type affects cost
Electrical & wiring $1,200 7% Includes permits
Installation labor $3,360 20% Varies by region
Permits & inspection $800 5% Local fees vary
Monitoring system $500 3% App-based tracking
Contractor overhead & profit $3,540 21% 15–25% margin
Total $16,800 100%

Global Cost Comparison by Country (5 kW System)

Country Avg Cost (USD) Cost/Watt Key Incentive Avg Payback
Australia $4,500 $0.90 STC certificates 4–5 years
India $3,200 $0.64 Central subsidy 40% 3–5 years
China $3,500 $0.70 Provincial subsidies 4–6 years
Germany $8,500 $1.70 Feed-in tariff / KfW loan 7–9 years
USA $14,000 $2.80 30% federal ITC 6–9 years
Japan $12,000 $2.40 METI subsidy 8–10 years
UK $9,500 $1.90 0% VAT on solar 8–10 years
Brazil $6,800 $1.36 Net metering 5–7 years
South Africa $7,200 $1.44 Load-shedding driven 5–7 years

25-Year Financial Projection (US 6 kW System)

Year Cumulative Savings System Cost (Net) Net Position Notes
1 $1,550 -$11,760 -$10,210 Year 1 savings
5 $8,400 -$11,760 -$3,360 Inverter may need check
7 $12,400 -$11,760 +$640 Break-even point
10 $18,200 -$11,760 +$6,440 55% ROI
15 $28,500 -$11,760 +$16,740 142% ROI
20 $40,200 -$11,760 +$28,440 242% ROI
25 $52,800 -$11,760 +$41,040 349% ROI

Assumes 3% annual electricity price increase, 0.5% annual panel degradation, no battery replacement.

4. Energy Independence & Grid Resilience

Beyond cost savings, home solar power systems provide a critical layer of energy security. In regions prone to grid outages — from extreme weather events to aging infrastructure — solar systems paired with battery storage offer true energy independence.

Grid Reliability Comparison: Grid-Only vs Solar+Storage

Scenario Grid-Only Solar Only (No Battery) Solar + Battery Storage
Normal operation Full power Full power (day), grid (night) Full power (24/7 self-sufficient)
4-hour grid outage (daytime) No power Partial power (sunlight only) Full power
4-hour grid outage (nighttime) No power No power Full power
24-hour grid outage No power Partial (daytime only) Full power (if sized correctly)
Multi-day outage No power Daytime only Full power (with EV charging)
Energy cost during outage N/A (generator fuel) $0 $0
Noise during operation Loud (generator) Silent Silent

Grid Outage Frequency by Region (2024 Data)

Region Avg Outages/Year Avg Duration (hours) Solar+Storage Value Proposition
USA (Texas) 12–18 3–8 Critical for summer/winter storms
USA (California) 8–14 2–6 PSPS events drive adoption
South Africa 200–300 2–4 Load-shedding: solar+storage essential
Brazil 15–25 2–5 Storm-prone regions benefit
Germany 1–3 0.5–1 Low outage risk; more for economics
Australia 6–10 1–3 Bushfire season resilience
Japan 3–6 1–4 Earthquake preparedness

For homes equipped with cabinet energy storage systems, grid resilience extends beyond just backup power — these systems can automatically switch between solar generation, battery storage, and grid power to optimize for cost and reliability simultaneously.

5. Home Energy Storage: The Game Changer

Adding battery storage transforms a solar power system from a daytime energy source into a 24/7 energy solution. In 2025, approximately 18% of new residential solar installations include battery storage — a figure expected to reach 45% by 2030.

Battery Storage Sizing Guide

Home Type Daily Usage (kWh) Recommended Battery Backup Hours Estimated Cost
Small (1-2 people) 10–15 kWh 5–7 kWh 8–10 hours $5,000–$7,000
Medium (3-4 people) 20–30 kWh 10–15 kWh 8–12 hours $8,000–$12,000
Large (5+ people) 35–50 kWh 15–20 kWh 8–12 hours $12,000–$16,000
With EV charging 50–70 kWh 20–30 kWh 6–10 hours $16,000–$24,000

Battery Technology Comparison (2025)

Technology Energy Density (Wh/kg) Cycle Life Cost ($/kWh) Safety Best For
LFP (Lithium Iron Phosphate) 150–180 6,000–10,000 $280–$350 Excellent Home storage (standard)
NMC (Nickel Manganese Cobalt) 200–250 3,000–5,000 $250–$320 Good Space-constrained homes
Semi-solid state 250–320 5,000–8,000 $450–$600 Excellent Premium homes (2025-2026)
Solid-state 300–450 8,000–12,000 $600–$800 Outstanding Future (2028-2030)
Sodium-ion 100–150 4,000–6,000 $200–$280 Excellent Budget home storage
Lead-acid (AGM) 30–50 500–1,200 $150–$250 Moderate Off-grid budget systems

Self-Consumption Rates: Solar vs Solar+Storage

System Configuration Self-Consumption Rate Grid Import Grid Export Annual Bill Reduction
Solar only (no battery) 30–40% High (evening) High (midday) 50–60%
Solar + 5 kWh battery 55–65% Moderate Low 70–80%
Solar + 10 kWh battery 70–80% Low Very low 85–92%
Solar + 15 kWh battery 80–90% Very low Minimal 92–96%
Solar + 20 kWh battery 90–95% Minimal Minimal 95–98%

💡 Innovation Spotlight: Solar+Storage as a Revenue Generator

In 2025, more than 12 GW of distributed energy resources are participating in Virtual Power Plant (VPP) programs globally. Homeowners with solar+storage can earn $500–$1,500 per year by allowing their battery to discharge during grid peak demand events. The US DOE projects VPP capacity to reach 80–160 GW by 2030, creating a massive opportunity for participating households.

6. Property Value & Market Appeal

Installing a home solar power system is not just an energy decision — it’s a real estate investment. Multiple studies confirm that solar-equipped homes sell faster and at higher prices than comparable non-solar properties.

Study/Source Market Property Value Increase Sale Speed Premium
Zillow Research (2024) USA +4.1% 20% faster
Lawrence Berkeley Lab USA +$15,000 (avg) Not measured
Solar Energy UK UK +2–4% Not measured
Realestate.com.au Australia +3–5% 15% faster
IEA PVPS Germany +2–3% 10% faster
Japan Real Estate Japan +3–4% Not measured

Home Buyer Preferences (2025 Survey)

Feature % Buyers Who Would Pay More Avg Willing to Pay Extra
Solar panels (existing) 67% $8,000–$12,000
Solar + battery storage 78% $12,000–$18,000
EV charging capability 71% $3,000–$5,000
Smart home energy management 54% $2,000–$4,000
Grid-tied + backup capability 62% $5,000–$8,000

7. Installation, Maintenance & System Longevity

One of the most underappreciated advantages of home solar power systems is their simplicity and durability. With no moving parts in the panels and minimal maintenance requirements, solar systems are among the most reliable energy investments available.

Installation Timeline

Phase Duration Key Activities
Site assessment 1–2 days Roof inspection, shading analysis, electrical assessment
System design 3–7 days Panel layout, inverter selection, permit drawings
Permitting 2–6 weeks Local building/electrical permits
Equipment delivery 1–2 weeks Panels, inverter, racking, battery
Installation 1–3 days Mounting, wiring, inverter setup
Inspection & PTO 1–3 weeks Utility inspection, Permission to Operate
Total timeline 4–10 weeks

25-Year Maintenance Schedule

Maintenance Item Frequency Cost DIY?
Panel cleaning 1–2×/year $150–$300 Yes (if safe roof access)
System monitoring check Monthly $0 (app-based) Yes
Inverter inspection Annual $100–$200 No (electrician)
Electrical connection check Every 3 years $200–$400 No (electrician)
Inverter replacement Year 10–15 $1,500–$3,000 No (installer)
Battery replacement (if equipped) Year 12–15 $4,000–$8,000 No (installer)
Panel-level inspection Every 5 years $300–$500 No (professional)
Racking integrity check Every 10 years $200–$400 No (professional)

Component Lifespan Expectations

Component Expected Lifespan Warranty (typical) Replacement Cost
Solar panels 25–30 years 25 years (80% output) $4,000–$6,000
String inverter 10–15 years 10 years $1,500–$2,500
Microinverter 20–25 years 25 years $200–$300/unit
Battery (LFP) 10–15 years 10 years (70% capacity) $4,000–$8,000
Mounting/racking 25–30 years 20 years $1,000–$2,000
Wiring & conduits 25+ years 10 years $500–$1,500
Monitoring system 10–15 years 5 years $300–$500

8. The Innovation Frontier: V2H, AI & Virtual Power Plants

🚀 Three Technologies Transforming Home Solar in 2025–2030

Beyond traditional solar+storage, three emerging technologies are creating entirely new value streams for homeowners: Virtual Power Plants (VPP)Vehicle-to-Home (V2H) charging, and AI-driven energy management. These innovations turn home solar systems from passive energy generators into active market participants.

Virtual Power Plants (VPP): Your Battery Earns Money

A Virtual Power Plant aggregates thousands of home solar+storage systems into a single dispatchable resource that grid operators can call upon during peak demand. Homeowners receive payment for allowing their battery to discharge during these events.

VPP Program Region Annual Earnings Requirements
Tesla VPP (California) USA $750–$1,200 Powerwall + grid connection
Sunrun VPP USA (multiple states) $500–$900 Sunrun battery + enrollment
South Australia VPP Australia $600–$1,000 Tesla Powerwall
Octopus Agile / Kraken UK $400–$800 Compatible battery + smart meter
sonnenCommunity Germany/Europe $300–$600 sonnen battery
Grid_rewards Australia (various) $400–$900 Approved battery system

Vehicle-to-Home (V2H): Your EV Is a Home Battery

V2H technology enables bidirectional charging — your electric vehicle’s battery can power your home during outages or peak-rate hours. With most EVs carrying 60–100 kWh of battery capacity (5–10× larger than typical home batteries), V2H transforms every EV into a massive home energy reserve.

Metric Home Battery (10 kWh) V2H (EV 77 kWh) Home Battery + V2H
Usable capacity 9 kWh 60 kWh (80% limit) 69 kWh
Backup duration (2 kW load) 4.5 hours 30 hours 34.5 hours
Cost of storage $8,000–$12,000 $2,500–$4,000 (charger) $10,500–$16,000
Daily cycling flexibility Limited (10 kWh) High (77 kWh) Maximum
Grid services potential Moderate High Very high
Best use case Daily self-consumption Backup + VPP revenue Full energy independence

The V2H bidirectional charging market was valued at $1.19 billion in 2025 and is projected to reach $6.93 billion by 2034, growing at a 21.5% CAGR. Major automakers including Ford, Hyundai, Nissan, and BYD are integrating V2H capability into new EV platforms.

V2H-Compatible EVs (2025)

Vehicle Battery Size V2H Power Output Backup Hours (2kW load)
Ford F-150 Lightning 98–131 kWh 9.6 kW 40–55 hours
Hyundai IONIQ 5 77.4 kWh 3.6 kW 25–30 hours
Nissan Leaf 39–62 kWh 6 kW 15–25 hours
BYD Seal (with V2H) 82.5 kWh 6 kW 25–30 hours
Mitsubishi Outlander PHEV 20 kWh 1.5 kW 8–10 hours
Rivian R1T 135 kWh 10 kW (planned) 55–65 hours

AI-Driven Smart Home Energy Management

Artificial intelligence is revolutionizing how home solar systems operate. AI algorithms analyze weather forecasts, electricity prices, household consumption patterns, and battery state to automatically optimize energy flows — deciding when to store, when to discharge, and when to sell to the grid.

AI Feature How It Works Annual Savings Availability
Load forecasting Predicts household demand using historical data $150–$300 Most smart systems
Time-of-use optimization Discharges battery during peak pricing $300–$600 Tesla, Sunrun, Enphase
Weather prediction Pre-charges battery before cloudy days $100–$200 Premium systems
VPP dispatch optimization Maximizes grid service revenue $400–$800 VPP-participating systems
EV charging optimization Charges EV from solar surplus $200–$400 Smart charger systems
Fault prediction AI detects system anomalies early $100–$300 (repair savings) Advanced monitoring
Total potential savings $1,250–$2,600/year

Emerging Innovation: Peer-to-Peer Energy Trading

P2P Platform Region Model Status (2025)
Powerledger Australia, SE Asia Blockchain P2P trading Commercial
SonnenCommunity Germany Community energy sharing Commercial
Vandebron Netherlands Direct producer-consumer Commercial
Brooklyn Microgrid USA (NY) Local energy market Pilot → Commercial
Piclo UK Flexibility trading Commercial
Energo Labs Australia Tokenized energy Pilot

9. Future-Proofing Your Solar Investment: 2025–2035 Roadmap

A well-designed home solar power system should remain relevant and adaptable for 25+ years. Understanding the technology roadmap helps homeowners make decisions that won’t become obsolete.

Technology Evolution Timeline

Technology 2025 Status 2027 Expected 2030 Expected 2035 Expected
Solar panel efficiency 21–22% (PERC) 23–25% (TOPCon) 25–28% (HJT/Perovskite) 28–32% (Tandem)
Panel cost ($/W) $0.28–$0.35 $0.22–$0.28 $0.18–$0.22 $0.12–$0.15
Battery cost ($/kWh) $280–$350 $200–$250 $120–$180 $80–$120
Smart inverter Basic grid-tie VPP-ready AI-optimized standard Autonomous grid agent
V2H integration Limited models 15% of new EVs 40% of new EVs 80% of new EVs
VPP participation 12 GW global 35–50 GW 80–160 GW 250+ GW
Home energy management App-based AI-predictive Autonomous Grid-interactive AI
Solid-state batteries Pilot production Niche commercial Mainstream premium Standard option

Decision Framework: Which System Should You Choose?

Homeowner Profile Recommended System Estimated Cost Annual Savings Key Benefit
Budget-conscious (first solar) 5 kW solar, no battery $9,800 (after ITC) $1,100–$1,500 Lowest payback period
Standard family home 6 kW solar + 10 kWh battery $18,500 (after ITC) $1,800–$2,400 70%+ self-consumption
EV owner family 8 kW solar + 15 kWh battery + V2H $24,000–$28,000 $2,500–$3,500 EV charged by solar
Off-grid / rural 10 kW solar + 30 kWh battery + generator $35,000–$45,000 Full independence Complete grid independence
Future-ready premium 10 kW solar + 20 kWh battery + V2H + VPP $30,000–$38,000 $3,500–$5,500 Maximum revenue + resilience
Existing solar upgrade Add battery + smart inverter $8,000–$15,000 $800–$1,500 additional VPP participation enabled

System Comparison: 20-Year Total Cost of Ownership

Cost/Benefit Item Grid-Only Solar Only (6kW) Solar+Storage (6kW+10kWh) Solar+Storage+V2H+VPP
Initial investment $0 $11,760 $18,500 $26,000
Inverter replacement (year 12) $0 $2,000 $2,000 $2,000
Battery replacement (year 14) $0 $0 $4,500 $3,500
Maintenance (20 years) $0 $2,500 $3,500 $4,000
20-year electricity cost $42,000 $18,500 $6,000 $2,000
VPP revenue (20 years) $0 $0 $6,000 $18,000
Property value increase $0 +$15,000 +$18,000 +$22,000
20-year net cost $42,000 $19,760 $6,500 -$4,500 (profit)

The data is clear: while grid-only energy costs continue to rise, a fully integrated solar+storage+V2H+VPP system can actually generate net profit over 20 years when accounting for VPP revenue and property value appreciation.

10. Huijue Solar+Storage Solutions & Action Plan

For homeowners and businesses looking to implement integrated solar power systems, Huijue Group offers a comprehensive range of energy storage solutions designed for residential, commercial, and industrial applications.

Huijue Product Portfolio for Home Solar+Storage

Product Line Capacity Range Application Key Features Best For
Residential BESS 5–20 kWh Home backup + self-consumption LFP cells, smart BMS, app control Standard family homes
Cabinet Energy Storage 50–200 kWh Large home / small business Modular, scalable, grid-ready Properties with high energy use
Container Energy Storage 200 kWh–1 MWh+ Commercial / community Turnkey, outdoor-rated, VPP-capable Multi-home / business complexes
Hybrid Inverter Systems 3–15 kW Solar integration MPPT, grid-tie, off-grid switch New solar installations

5-Step Action Plan for Homeowners

Step Action Timeline Key Consideration
1 Assess your energy needs Week 1 Review 12 months of electricity bills
2 Evaluate solar potential Week 1–2 Roof orientation, shading, available space
3 Choose system configuration Week 2–3 Solar-only vs solar+storage vs full integration
4 Research incentives & financing Week 3–4 Tax credits, rebates, PPA vs purchase
5 Get quotes & select installer Week 4–6 Compare 3+ quotes, check certifications

Whether you’re starting with a basic solar setup or building a fully integrated energy ecosystem with V2H and VPP participation, the key is to design for future expandability. A modular approach — starting with solar panels and adding battery storage, smart management, and V2H capability over time — allows you to scale your investment as technology matures and costs decline.

Ready to explore integrated solar+storage solutions? Visit our products page to browse the full range, or contact our team for a customized energy assessment.

Start Your Solar Journey Today

From rooftop solar panels to cabinet energy storage and container-scale solutions, Huijue Group provides end-to-end energy independence for homes and businesses worldwide.

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FAQ: Home Solar Power Systems

Q1: How much does a home solar power system cost in 2025?

A: A typical 6 kW residential solar system costs $16,800 before incentives and $11,760 after the 30% US federal tax credit (or equivalent local incentives). Costs vary significantly by country — from $3,200 in India to $14,000 in the US for a 5 kW system. Adding battery storage increases the total by $5,000–$15,000 depending on capacity.

Q2: How long does it take for home solar to pay for itself?

A: The average payback period ranges from 4–5 years in Australia and India to 6–9 years in the US and Europe. By 2030, as panel costs decline further and electricity prices rise, payback periods are expected to shorten to 4–6 years globally. Adding battery storage extends payback by 1–2 years but increases long-term savings.

Q3: Can I use my EV to power my home with V2H technology?

A: Yes. Vehicle-to-Home (V2H) technology enables bidirectional charging, allowing your EV’s battery (typically 60–100 kWh) to power your home. Compatible vehicles include the Ford F-150 Lightning, Hyundai IONIQ 5, and Nissan Leaf. With a 77 kWh EV battery, you can provide 25–30 hours of backup power at 2 kW load — far exceeding most home battery systems.

Q4: What is a Virtual Power Plant and how can I participate?

A: A Virtual Power Plant (VPP) aggregates thousands of home solar+storage systems into a dispatchable grid resource. When grid demand peaks, the VPP discharges participating home batteries and pays homeowners $500–$1,500 per year. Programs like Tesla VPP (California), South Australia VPP, and sonnenCommunity (Germany) are available now. The US DOE targets 80–160 GW of VPP capacity by 2030.

Q5: Do solar panels work during a power outage?

A: Solar panels alone shut off during grid outages for safety reasons (anti-islanding). However, solar+storage systems with a backup-capable inverter automatically switch to island mode, powering your home from battery and solar. Systems with V2H can extend backup duration to 25+ hours using your EV’s battery.

Q6: Will adding solar increase my property value?

A: Yes. Studies from Zillow, Lawrence Berkeley Lab, and Solar Energy UK consistently show that homes with solar sell for 2–5% more than comparable non-solar homes. In the US, the average value increase is approximately $15,000. Homes with solar+storage command even higher premiums — 78% of buyers say they would pay extra for a home with both solar and battery storage.