How to calculate the investment and return on investment in solar energy?

To determine the configuration of a solar photovoltaic system to serve a house with 5 rooms, 4 residents, 4 air conditioners, 3 computers, 3 televisions, and additional smart devices like tablets, we need to estimate the daily energy consumption.

1. Energy Consumption Assessment

1.1 Air Conditioners

Assuming each air conditioner has a power rating of 1,500 watts and is used for 8 hours daily: 4 units×1,500 W×8 hours=48,000 Wh/day=48 kWh/day

1.2 Computers

Assuming each computer has a power rating of 300 watts and is used for 8 hours daily: 3 computers×300 W×8 hours=7,200 Wh/day = 7.2 kWh/day

1.3 Televisions

Assuming each television has a power rating of 100 watts and is used for 5 hours daily 3 televisions×100 W×5 hours=1,500 Wh/day=1.5 kWh/day

1.4 Smart Devices (Tablets, etc.)

Assuming an average of 1 kWh per day for additional smart devices: 1 kWh/day

1.5 Average Energy Consumption of Residents

For lighting, kitchen appliances, and other electronics, assuming an average of 3 kWh per resident per day: 4 residents×3 kWh=12 kWh/day

1.5 Total Daily Energy Consumption of the household

Air Conditioners: 48 kWh
- Computers: 7.2 kWh
- Televisions: 1.5 kWh
- Smart Devices (Tablets, etc.) : 1 kWh
- Average Energy Consumption of Residents (other electric services): 12 kWh
Total = 69.7 kWh/day

1.6 Photovoltaic System Sizing

1.6.1 Solar Panels Required

Assuming an average solar insolation of 5.5 peak sun hours per day in Texas (source: EnergyBot): Energy required per day = 69.7 kWh/day

Energy required per peak sun hour = 69.67 Kw/ 5.5 hours ≈ 12.67 kW

Assuming each solar panel has a power rating of 330 watts (0.33 kW):

Rounding up, we need 39 panels.

1.7 Storage System (Batteries)

To support 40% of the energy demand during the night:

Energy needed at night=69.7 kWh×0.40 = 27.88 kWh

Assuming each battery has a capacity of 5 kWh:

Number of batteries required = 27.88 kWh5 / kWh/battery ≈ 5.6 batteries

Rounding up, we need 6 batteries.

Configuration Summary

Solar Panels: 39 panels of 330 W each
Energy Generated Daily: Approximately 69.7 kWh
Batteries: 6 batteries of 5 kWh each, providing a total storage capacity of 30 kWh

2. Investments assessment to implement the system

To estimate the investment required for a solar photovoltaic (PV) system in Texas, USA, with the configuration mentioned, we need to consider the costs of solar panels, inverters, batteries, mounting structure and cables, labor and installation, and other expenses. Let’s break down each component[1]:

2.1 Solar Panels

Quantity: 39 panels of 330 W each
Price per panel: $250
Total cost of panels: 39 x $250 = $9,750

2.2 Inverters

Required power: 12.67 kW (considering a margin of safety, using 13 kW inverters)
Price per 13 kW inverter: $3,000
Total cost of inverters: $3,000

2.3 Batteries

Quantity: 6 batteries of 5 kWh each
Price per 5 kWh battery: $3,500
Total cost of batteries: 6 x $3,500 = $21,000

2.4 Mounting Structure and Cables

Estimated cost (approximately 10% of the cost of panels): 0.10 x $9,750 = $975

2.5 Labor and Installation

Estimated cost (approximately 15% of the total cost of equipment):
Total equipment cost: $9,750 + $3,000 + $21,000 + $975 = $34,725
Labor and installation cost: 0.15 x $34,725 = $5,208.75

2.6 Other Expenses (Design, Homologation, Taxes, etc.)

Estimated cost: $2,500

Summary of Costs

Solar Panels: $9,750
Inverters: $3,000
Batteries: $21,000
Mounting Structure and Cables: $975
Labor and Installation: $5,208.75
Other Expenses: $2,500

Total estimated cost: $42,433.75

This estimate provides a comprehensive view of the investment required for the solar PV system, considering the average costs in Texas. Adjustments might be necessary based on specific project conditions and current market prices.

3. Pay back assessment

To estimate the payback period for a solar photovoltaic (PV) system in Texas, we need to consider the cost of electricity, the household’s energy consumption, and the savings generated by the PV system.

3.1 Annual Energy Consumption

Based on the previous estimate, the daily energy consumption is 69.7 kWh.

Annual energy consumption: 69.7 kWh/day × 365 days/year = 25,440.5 kWh/year

3.2. Average Electricity Price in Texas

Electricity prices in Texas vary depending on the utility and the consumption tier. Let’s assume an average price of $0.12 per kWh (source: EnergyBot).

3.3 Annual Savings with the PV System

Annual savings: 25,440.5 kWh × $0.12/kWh = $3,052.86

3.4 Calculating the Payback Period

The estimated total cost of the PV system is $42,433.75.

Payback period (in years): Total cost / Annual savings = $42,433.75 / $3,052.86 ≈ 13.9 years

Considerations

Price Variation: Electricity prices may change over time, affecting the payback period.
Maintenance and Performance: Proper maintenance and the efficiency of the solar panels over time will also impact the savings.
Tariffs and Incentives: Check for any tax incentives, subsidies, or financing options that could reduce the initial investment cost.

Summary

Based on the estimated consumption and the average electricity price in Texas, the payback period for the investment in a solar PV system for the described household would be approximately 13.9 years. After this period, the savings generated by the system represent a significant financial return, in addition to contributing to environmental sustainability.

The figures shown are estimates based on average market prices and may vary depending on the location, specific project conditions, and chosen vendors. It is always recommended to get detailed quotes from specialized companies for a more accurate analysis. Choosing the right equipment for your needs and the best contractors and investment solutions, make sure your integrator is registered on the EOS platform that makes your investment in solar energy more accessible and attractive (EOS Loan, 2024).

References