Final answer:
Homeowners typically recover their energy investment in solar panels after around 5 years, and financial payback usually occurs in about 9 years, but this can vary due to factors like geographical location, energy costs, and available incentives.
Step-by-step explanation:
To determine how long it takes homeowners to recover their investment in solar panels, one must consider several factors, including the energy return on energy invested (EROEI), the cost of the solar panel system, the amount of electricity generated, and the cost of electricity. If a solar panel has an EROEI of 6:1, it implies that for each unit of energy used to manufacture the panel, six units of energy will be produced over its lifetime. It takes five years of the panel's output to 'pay off' the energy invested in its production. Assuming a usual operative panel life of 30 years, these first five years would be spent recovering the initial energy investment.
Moreover, for a financial perspective, if a solar system costs about $3,000 per kWp (peak capacity) and we assume a daily production of 6 hours of full-sun equivalent and an electricity cost of $0.15 per kWh, the value per day would be $0.90 (6 hours * $0.15). To recover a $3,000 investment, it would take approximately 3333.33 days, or roughly 9 years, not accounting for additional factors like potential state and federal incentives which might reduce the payback time. However, one needs to consider that during months like December in the northern hemisphere, where there is less sunlight, the system's generation capacity decreases, thus potentially lengthening the payback time. Estimating the right system size and accounting for varying sun exposure throughout the year can help in computing a more accurate payback period.