Let's break down the cost implications of switching to solar-powered street lights for your parking lot project, considering your situation

Arguments AGAINST switching to solar (likely more expensive in your case):
Already Purchased Fixtures

You've already invested in LED fixtures. Switching now means eating that cost, making the initial cost of the solar option significantly higher. This is a HUGE factor.

Photometric Redesign and Layout Changes

Solar streetlights likely have different light distribution patterns than your chosen LEDs. A complete photometric study and redesign of the lighting layout is required. This adds more engineering time and potential material costs (changing pole locations, etc.).

Potentially Higher Initial Cost

Solar streetlights are typically more expensive per fixture than standard LED fixtures. This is due to the solar panel, battery, charge controller, and robust housing needed for these systems.

Battery Replacement Costs

Solar streetlight batteries have a limited lifespan (typically 5-7 years). Budgeting for these replacements is crucial. This is a recurring cost that the standard LED system won't have in the same timeframe.

System Complexity and Maintenance

Solar systems have more components that can fail (panel, battery, charge controller). This can translate into higher maintenance costs and potentially longer downtime. While LED fixtures themselves are reliable, the supporting solar components add a layer of complexity.

Performance Variability

Solar performance is dependent on sunlight. Shading from trees or buildings can significantly reduce light output. You need to consider the site's sun exposure throughout the year, especially during the winter months when sunlight is less abundant. This could mean the solar lights are less effective during times when you really need them (e.g., winter evenings).

Luminosity (brightness) might not be sufficient

Solar streetlights often have difficulty providing sufficient brightness. The lights designed by the engineering firm may be far brighter.

Circumstances where solar could be a cost-saving strategy in the long run (but probably not for you now)



No existing grid connection

If you had to trench power to the parking lot, the cost of running the electrical service could be very high. Solar could be competitive in this situation, but you've already designed for a grid-tied system.

High electricity rates

If your electricity rates are exceptionally high and expected to rise significantly, the long-term savings from eliminating electricity bills might outweigh the higher initial costs and maintenance of solar. However, LED lighting is already very energy efficient, so the savings might not be as dramatic as you think.

Strong "green" mandate

If your client has a strong commitment to sustainability and is willing to pay a premium for environmentally friendly solutions, solar might be considered despite the potential cost disadvantages. However, even then, it should be a well-informed decision.

Significant government incentives

If there are generous government rebates or tax credits for solar installations in your area, this could offset some of the initial costs.

In your specific case

Given that you've already purchased the LED fixtures and the engineering firm has designed the lighting system, switching to solar at this point is almost certainly not a cost-saving strategy. You would be throwing away money on the purchased fixtures, incurring additional engineering costs, and likely facing higher initial and long-term operating costs with the solar system.

Recommendation


Explain the situation clearly to the client. Emphasize the cost of the already purchased fixtures and the likely higher overall cost of switching to solar at this stage.2. Provide a cost comparison (if requested)

If the client insists on exploring solar, create a detailed cost comparison that includes: Cost of the existing LED fixtures (this is a sunk cost, but needs to be acknowledged). Cost of the solar streetlight fixtures, including batteries. Engineering costs for the photometric redesign. Installation costs for both systems. Estimated electricity costs for the LED system over a 20-year period (or similar timeframe). Estimated battery replacement costs for the solar system over the same timeframe. Maintenance costs for both systems.3.

Highlight the performance considerations

Explain how solar performance can be affected by weather and shading, and how this might impact the lighting quality of the parking lot.

In summary, switching to solar at this point is highly unlikely to be a cost-saving measure. Sticking with the planned LED lighting system is the most logical and cost-effective approach. Flag for review