When does solar + battery pay back?

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. Flip one at a time toward extreme values to feel which ones move the needle most for your situation.

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.