Solar Capacity Calculation for Housing Society
- Posted by Infisol Energy
- February 17, 2026
How Much Solar Capacity Does a 100-Flat Society Need?
Rising electricity tariffs and increasing maintenance costs are pushing housing societies to explore solar power seriously. But before installation, the most important question is:
How much solar capacity does a 100-flat housing society actually need?
The answer depends on electricity consumption, rooftop feasibility, metering structure, and financial planning. A proper solar capacity calculation for housing society projects ensures the system is technically accurate and financially viable.
Step 1 – Analyse Electricity Consumption
Solar sizing always starts with data.
For most 100-flat societies, solar is installed primarily for common area consumption, including:
- Lifts
- Water pumps
- Parking and staircase lighting
- Security systems
- Clubhouse or gym
- Sewage treatment plant
A typical 100-flat society may consume:
- 18,000 to 30,000 units per month
- 2.2 to 3.5 lakh units annually
The last 12 months of electricity bills should be analysed before capacity planning.
Step 2 – Convert Units into Required Solar Capacity
In Maharashtra conditions, 1 kW of rooftop solar generates approximately 1,350 to 1,500 units annually.
Using a conservative estimate of 1,400 units per kW:
If annual consumption is 3,00,000 units:
3,00,000 ÷ 1,400 = approximately 214 kW
So most 100-flat societies require between 150 kW to 220 kW, depending on their energy usage.
This forms the core of solar capacity calculation for housing society planning.
Step 3 – Rooftop Area Requirement
Capacity must align with rooftop availability.
On average:
- 1 kW requires 90 to 100 sq ft
- 200 kW requires roughly 18,000 to 20,000 sq ft
Before finalising system size, a technical team must conduct:
- Shadow analysis
- Structural load assessment
- Panel layout optimisation
Ignoring rooftop constraints often leads to unrealistic sizing.
Step 4 – Connected Load vs Energy Consumption
Many societies confuse connected load with energy usage.
- Connected load is measured in kW
- Electricity consumption is measured in kWh
Solar sizing is based on annual energy consumption, not just sanctioned load.
A detailed bill study ensures the plant is neither undersized nor oversized.
Step 5 – Role of Virtual Net Metering
Large housing societies often exceed common meter limits. In such cases, virtual net metering becomes important.
Policies regulated by the Maharashtra Electricity Regulatory Commission allow solar generation to be distributed across multiple meters under approved conditions.
Billing and approvals are managed by Maharashtra State Electricity Distribution Company Limited.
Virtual net metering enables:
- Larger plant installation
- Fair distribution of solar benefits
- Better utilisation of rooftop space
Learn more about virtual net metering in Maharashtra.
Investment and Long-Term Savings Framework
Solar for housing societies should be evaluated as a long-term infrastructure investment.
Project investment depends on:
- Required solar capacity
- Rooftop structure type
- Electrical integration complexity
- Inverter and protection design
- Net metering configuration
Rather than focusing on upfront numbers, societies should analyse annual savings potential.
If a 200 kW plant generates around 2.8 lakh units annually and grid tariffs remain high, the savings can significantly reduce common electricity expenses.
Well-planned projects typically achieve payback within a few years. After that, the system continues generating savings for 20 to 25 years.
CAPEX vs RESCO Model for Housing Societies
Housing societies can choose between:
CAPEX Model
Society invests upfront and retains full financial benefit.
RESCO Model
Developer invests and society pays for solar energy consumed at agreed rates.
The right structure depends on financial planning and long-term objectives.
Common Mistakes in Solar Planning for Societies
- Oversizing without rooftop verification
- Ignoring export limits
- Skipping structural evaluation
- Choosing vendors purely on lowest price
- Not understanding metering policy
Professional solar capacity calculation for housing society projects prevents these issues.
Ideal Capacity Range for a 100-Flat Society
While each case differs, most 100-flat societies fall within:
- 120 kW minimum viable range
- 150 to 220 kW optimal range
- Higher capacity if consumption is significantly above average
Final sizing must be based on:
- Bill analysis
- Roof feasibility
- Policy compliance
- Financial modelling
Why Technical Feasibility Study Is Essential
Solar implementation for housing societies requires:
- Detailed energy audit
- Rooftop structural assessment
- Generation modelling
- Policy alignment
- ROI projection
A structured feasibility study ensures the system delivers maximum savings without regulatory complications.
Conclusion
- Optimal generation
- Faster payback
- Compliance with net metering policies
- Long-term reduction in maintenance burden
Frequently Asked Questions
How much solar capacity is required for a 100-flat housing society?
Most societies require between 150 kW and 220 kW depending on annual electricity consumption.
Can housing societies use virtual net metering?
Yes, subject to regulatory approval and utility compliance, virtual net metering allows distribution of solar benefits across multiple meters.
How do you calculate solar capacity from electricity bills?
Divide annual electricity consumption by expected yearly generation per kW in your region.
What rooftop area is required for a 200 kW solar plant?
Approximately 18,000 to 20,000 sq ft, depending on panel layout and spacing.
A Practical Next Step
Every housing society has a unique load pattern, rooftop structure, and financial objective. A properly engineered solar capacity calculation ensures your system is optimally sized for maximum savings and policy compliance. If your 100-flat society is evaluating solar, a detailed feasibility study is the first step toward reducing long-term electricity expenses. Connect with Infisol’s technical team to assess your rooftop potential and build a structured, future-ready solar plan for your community.