I. Core Cost Structure: Battery and System Expenditure Breakdown

　　1. Battery Cost (40%-55% of the Total Budget)

　　Capacity and Price Linkage: A 20kW home solar system typically has a capacity of 25-32kWh (including 10%-25% redundancy). In 2025, the unit cost of mainstream lithium batteries was approximately 900-1100 RMB/kWh, corresponding to a battery cost of 22,500-35,200 RMB. If a long-cycle-life model (≥6,000 cycles) is selected, the cost will increase by 10%-15%.

　　Technology Differences: Lithium iron phosphate batteries have become the mainstream in home use due to their safety and slow degradation, and their cost is 5%-8% lower than ternary lithium batteries. While the emerging metal-air battery has a theoretical cost of only $20-45/kWh, it has not yet achieved large-scale home use by 2025 and is not currently included in the regular budget.

　　2. PV Array Support Costs (25%-35% of the Total Budget)

　　Module and Inverter Expenses: A 20kW battery requires a 22-28kW PV array (capacity-to-capacity ratio of 1.1-1.4). In 2025, PV module prices were approximately 0.7 yuan/watt, and inverters were approximately 0.15 yuan/watt. This translates to module costs of 15,400-19,600 yuan, and inverter costs of 3,300-4,200 yuan.

　　Supplementary Material Costs: Support materials such as brackets (0.1 yuan/watt), cables, and distribution boxes total approximately 0.15-0.2 yuan/watt. For a 22-28kW array, the corresponding auxiliary material costs are 3,300-5,600 yuan.

　　3. Installation and Service Costs (15%-20% of the Total Budget)

　　Labor Costs: This includes site surveys, string installation, grid-connection commissioning, and other aspects. The industry average price in 2025 was approximately 0.3-0.4 RMB/W, and labor costs for a 22-28kW system ranged from 6,600-11,200 RMB. Complex rooftops (e.g., sloped roofs or those with multiple obstructions) require an additional 20%-30% labor cost.

　　Other Expenses: Preliminary procedures (e.g., grid registration) cost approximately 0.1-0.2 RMB/W. A maintenance reserve of 5% of the total budget (approximately 2,000-5,000 RMB) is recommended.

　　II. Cost Factors: Scenario-Based Analysis

　　1. Installation Environment Complexity

　　Roof Conditions: Flat roof installation requires no additional reinforcement and is relatively low cost. Sloped roofs require custom brackets, increasing costs by 5%-8%. Older buildings require load-bearing modifications, costing an additional 3,000-8,000 RMB.

　　Climate: High-altitude, high-wind areas require brackets with a wind resistance rating of 15 or higher, increasing costs by 10%-12%. Low-temperature areas require the installation of a battery insulation module, costing an additional 2,000-4,000 RMB.

　　2. Configuration Selection

　　Capacity Ratio Adjustment: A base configuration with a capacity ratio of 1.1 (22kW array) is 25%-30% cheaper than a high-efficiency configuration with a capacity ratio of 1.4 (28kW array), but the charging efficiency decreases by 30% in low-light environments.

　　Efficiency Level Differences: High-efficiency photovoltaic panels (≥20%) cost 15%-20% more than conventional models (12%-16%), but they offer over 25% higher annual power generation, resulting in better long-term returns.

　　3. Policy and Market Fluctuations

　　Raw Material Impact: Every 10% fluctuation in lithium prices results in an 8%-10% change in battery costs. Battery cell prices are expected to rise slightly in 2025 due to growing demand, but this impact will be partially offset by declining system integration costs.

　　Subsidy Policies: Some regions offer subsidies of 10%-20% of initial investment for household energy storage, or provide a per-kilowatt-hour (kWh) electricity discharge subsidy, which can significantly reduce actual expenditures.

　　III. Home Budget Range and Example

　　1. Basic Configuration Budget (25kWh Battery + 22kW Array)

　　Core Expenses: Battery 22,500-27,500 RMB + PV Panels 15,400 RMB + Inverter 3,300 RMB + Supplies 3,300 RMB + Labor 6,600 RMB = 51,100-56,100 RMB

　　Other Expenses: Processing 2,200 RMB + Maintenance 2,500 RMB = 4,700 RMB

　　Total Budget: Approximately 55,800-60,800 RMB, suitable for the basic electricity needs of a family of three (average daily load 3-5kW).

　　2. High-Efficiency Configuration Budget (32kWh Battery + 28kW Array)

　　Core Expenses: Battery 28,800-35,200 RMB + PV Panels 19,600 RMB + Inverter 4,200 RMB + Supplies 5,600 RMB + Labor 11,200 RMB = 69,400-75,200 RMB

　　Other Expenses: Processing 2,800 RMB + Maintenance 3,800 RMB = 6,600 RMB

　　Total Budget: Approximately 76,000-81,800 RMB, suitable for a family of five or high-power appliances (including air conditioners and electric water heaters).

　　3. Additional Budget for Extreme Environments

　　Cold and Snowy Regions (requires insulation and snow-resistant brackets): Add 5,000-8,000 RMB to the high-efficiency configuration, for a total budget of 81,000-89,800 RMB.

　　Old buildings (requiring load-bearing renovation): Add 3,000-8,000 RMB to the basic configuration, for a total budget of 58,800-68,800 RMB.

　　IV. Cost Optimization Strategies: Balancing Budget and Returns

　　1. Configuration Optimization

　　Precise Capacity-to-Capacity Ratio: For high-insolation areas (≥2,800 hours of annual sunshine), choose a capacity-to-capacity ratio of 1.1-1.2 times; for low-insolation areas (<2,000 hours), choose a capacity-to-capacity ratio of 1.3-1.4 times to avoid overinvestment or insufficient energy replenishment.

　　Phased Upgrade: Prioritize the installation of a base-capacity battery (25 kWh). Later, expand capacity based on electricity consumption growth, reducing the initial budget by 20%-25%.

　　2. Installation and Procurement Timing

　　Centralized Procurement Discounts: By collaborating with surrounding users to purchase modules and batteries in bulk, you can receive a 5%-10% price discount, reducing per-household costs.

　　Off-peak installation: Avoid the summer construction peak (June-August), and labor costs can be reduced by 15%-20%; choose to purchase battery raw materials during the low price period (usually Q1) to save 5%-8% of costs.

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