This may have been spoken about before. Here`s the thing. I had a PV battery storage system installed in August last year but did not get much generation due to teething issues. Ok I am thinking that due to the unpredictable weather especially in Scotland. If I take my usage for 2024 usage cost from my monthly bills could I just take what money I get back and tally it up over 12 months and divide the installation hardware costs and divide by the yearly saving. What is the best way to calculate my payback.
Solar system payback
- Thread starter Stratto
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Hedges
I See Electromagnetic Fields!
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"Money you get back"? Are you paid something for use of the battery?
You mention what you pay for bills, but not whether battery can store what you use in a day, or more or less.
Battery has some kWh capacity you can use.
Do you have a spread between peak rates and off-peak, so you can store power for later when it would cost more?
If so, that spread multiplied by battery capacity is how much money the battery can save you per day. Maybe limited by your consumption during peak rates, or maybe you can backfeed for credits.
Some batteries would reach their end of cycle life before utility bill savings add up to as much as purchase price. LG RESU-10H, it looks like $0.50/kWh of cycles over its life. Others may come in at $0.05/kWh.
You mention what you pay for bills, but not whether battery can store what you use in a day, or more or less.
Battery has some kWh capacity you can use.
Do you have a spread between peak rates and off-peak, so you can store power for later when it would cost more?
If so, that spread multiplied by battery capacity is how much money the battery can save you per day. Maybe limited by your consumption during peak rates, or maybe you can backfeed for credits.
Some batteries would reach their end of cycle life before utility bill savings add up to as much as purchase price. LG RESU-10H, it looks like $0.50/kWh of cycles over its life. Others may come in at $0.05/kWh.
Welcome to the forum!
You're brave to do solar in Scotland, between your latitude and weather.
In calculating ROI for solar, many people forget to include the "opportunity cost" of not investing elsewhere. Eg: paying off mortgages/loans or even bank interest.
You're brave to do solar in Scotland, between your latitude and weather.
In calculating ROI for solar, many people forget to include the "opportunity cost" of not investing elsewhere. Eg: paying off mortgages/loans or even bank interest.
Rarely people include opportunity cost in their calculations 
https://docs.google.com/spreadsheets/d/14adTRsoK_6cY6lLonZz6q27T2ZnmWHg5mtCzkDAme68/edit?usp=sharing is a ROI calculator that should give you an idea on RoI (It does include opportunity cost).
The way you can measure your ROI is:
1) Take all the power that you generated and used and multiply it with your utility rate. This is the amount you saved by not spending
2) Take all the credit you got for exports and add it to 1)
3) Take the money you invested and subtract the amount the money would have made for your otherwise (invested in something else, or not paying interest on another outstanding loan)
https://docs.google.com/spreadsheets/d/14adTRsoK_6cY6lLonZz6q27T2ZnmWHg5mtCzkDAme68/edit?usp=sharing is a ROI calculator that should give you an idea on RoI (It does include opportunity cost).
The way you can measure your ROI is:
1) Take all the power that you generated and used and multiply it with your utility rate. This is the amount you saved by not spending
2) Take all the credit you got for exports and add it to 1)
3) Take the money you invested and subtract the amount the money would have made for your otherwise (invested in something else, or not paying interest on another outstanding loan)