Solar + Battery Storage ROI Calculator
When does solar + battery pay back?
Calculate solar plus battery ROI from system cost, generation, electricity rate, and export rate — the payback period for the combined install.
What this tool does
This calculator models the financial return of a solar and battery storage system over a chosen time period. It estimates annual savings from self-consumed electricity (valued at your retail rate) plus income from any surplus energy exported to the grid (at the feed-in rate you receive). The tool then calculates total financial benefit across the system lifespan, payback period, and net return on investment. Results are most sensitive to system cost, annual generation output, your electricity rate, and the percentage of generated power you use on-site rather than export. A typical scenario might compare a domestic installation with moderate self-consumption against its upfront cost. The calculator assumes stable electricity and feed-in rates over the period modeled and does not account for maintenance costs, degradation, or changes in consumption patterns. Results are for financial illustration only.
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Formula Used
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Calculations or display — let us know.
Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
A combined solar panel and battery system for a typical home costs 10,000-18,000 installed, generates 3,500-5,000 kWh annually, and can self-consume 60-80% of that generation with battery storage. This calculator shows financial ROI based on your specific electricity rates and system economics.
A 14,000 system generating 4,000 kWh at a 0.28/kWh electricity rate with 70% self-consumption and 0.15/kWh export rate produces 784 self-consumption savings + 180 export income = 964 annual benefit. Payback is about 14.5 years, over 25 years the net ROI is roughly 10,100.
The tool is sensitive to assumptions. Higher electricity rates compress payback dramatically - at 0.35/kWh the same system pays back in 12 years. Export rates matter less because self-consumption is the main win. Over 25 years (typical panel warranty), most systems pay back and deliver meaningful ROI, though the timeline is longer than marketing often suggests.
Quick example
With system cost of 14,000 and annual generation of 4,000 (plus electricity rate per kwh of 0.28 and self-consumption of 70%), the result is 10,100.00. Change any figure and watch the output shift — it's often more useful to see the pattern than to memorise the formula.
Which inputs matter most
You enter System Cost (Installed), Annual Generation (kWh), Electricity Rate per kWh, Self-Consumption, and Feed-in Rate per kWh. Not every input has equal weight. Adjusting one input at a time toward extreme values shows which ones move the result most.
What's happening under the hood
Self-consumed kWh × rate = savings. Exported kWh × feed-in = export income. Annual benefit = savings + income. Total benefit = annual × years. Net ROI = total benefit - system cost. The formula is listed in full below. If the number looks off, you can retrace the calculation by hand — that's the point of showing the working.
Running the sensitivity
Energy prices, usage patterns, and grant availability all move the payback figure. Test at least two scenarios — current rates and a rate 20% higher — to see whether the decision holds up across plausible futures.
What this doesn't capture
Carbon reduction, health benefits, and local air quality have real value the financial figure doesn't price. The calculation gives the money side honestly; for the full picture, note the non-financial benefits alongside.
££14,000 system generating 4,000kWh at ££0.28/kWh over 25 yearsyrs = 10,100.00.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
The calculator computes annual financial benefit by splitting generated electricity into two streams. Self-consumed generation (the self-consumption percentage of total annual output) is valued at the electricity rate, representing avoided grid purchases. Remaining generation exported to the grid is valued at the feed-in rate. These two revenue components are summed to produce annual benefit. Total benefit across the specified time horizon is calculated by multiplying annual benefit by the number of years. Net return on investment is derived by subtracting the installed system cost from total benefit. The model assumes constant electricity and feed-in rates throughout the period, treats self-consumption and export percentages as fixed, and does not account for system degradation, maintenance costs, inflation, or changes in consumption patterns.
References
Frequently Asked Questions
What's realistic annual generation?
Does battery storage add enough value?
What happens after 25 years?
Are government incentives included?
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