Trees, shade, weather-factor (clouds), effective day-light hours - all effect PV output and change depending on time of year.
(Best case: 8.0 effective day-light hours in December, and 11.0 effective day-light hours in June)
Without being a math wizard and doing calculations - you need real outputs based on other local installed systems.
Ask your contractor for similar sized systems and the real KWh monthly outputs. Ask for 2-3 years of outputs, as KWh output changes considerably over the months/seasons. Calculate the annual average KWh/month and multiply by your electric rate. That'll be your average PV savings per month, then compare to the total costs and ROI.
If the 'other' system is a difference PV size - be sure to adjust the numbers accordingly.
...or reference the SunnyPortal for real-outputs (previously linked).
Other considerations:
The future costs? Consider that the cost of electricity will only go up in the future.
So a simple-ROI isn't the best approach. The real saving may be in 10 years when the KWh price is ...double?
How's your roof?
There's no point installing a PV system over a roof that's 3 years from being replaced.
It'll have to be completely removed for roof replacement, then re-installed. (insert: damaged?)
A standing-seam metal roof would be ideal, as standing seam don't have exposed fasteners and will last 50+ years.
Metal roofs with exposed fasteners are only good for 15-20 years, as the screws start getting loose and start slowly leaking.
Can you DIY?
If you can get the racking/panels and install yourself (no labor or bank loan) - then the ROI is about 5-6 years.
If you can DIY - then it's a crazy good deal.
For further reading:
https://www.okshooters.com/threads/solar-panels-for-home-energy.180456/
https://www.okshooters.com/threads/solar-energy-system.157153/
https://www.okshooters.com/threads/solar-systems.121164/
(Best case: 8.0 effective day-light hours in December, and 11.0 effective day-light hours in June)
Without being a math wizard and doing calculations - you need real outputs based on other local installed systems.
Ask your contractor for similar sized systems and the real KWh monthly outputs. Ask for 2-3 years of outputs, as KWh output changes considerably over the months/seasons. Calculate the annual average KWh/month and multiply by your electric rate. That'll be your average PV savings per month, then compare to the total costs and ROI.
If the 'other' system is a difference PV size - be sure to adjust the numbers accordingly.
...or reference the SunnyPortal for real-outputs (previously linked).
Other considerations:
The future costs? Consider that the cost of electricity will only go up in the future.
So a simple-ROI isn't the best approach. The real saving may be in 10 years when the KWh price is ...double?
How's your roof?
There's no point installing a PV system over a roof that's 3 years from being replaced.
It'll have to be completely removed for roof replacement, then re-installed. (insert: damaged?)
A standing-seam metal roof would be ideal, as standing seam don't have exposed fasteners and will last 50+ years.
Metal roofs with exposed fasteners are only good for 15-20 years, as the screws start getting loose and start slowly leaking.
Can you DIY?
If you can get the racking/panels and install yourself (no labor or bank loan) - then the ROI is about 5-6 years.
If you can DIY - then it's a crazy good deal.
For further reading:
https://www.okshooters.com/threads/solar-panels-for-home-energy.180456/
https://www.okshooters.com/threads/solar-energy-system.157153/
https://www.okshooters.com/threads/solar-systems.121164/