Small-scale hydropower return.

Small-scale hydropower (micro-hydro) generates electricity from flowing water - streams, rivers, mill races. Installation cost 20-100k depending on head height and flow rate. Output: 5-100 kW for typical micro-hydro. Revenue from: self-consumption savings + feed-in tariff (Smart Export Guarantee in). Lifespan 25-50+ years.

50,000 installation generating 60,000 kWh/year. At 0.30/kWh self-consumption + 0.05 SEG export = 0.35 blended rate. Annual revenue 21,000. Maintenance 2,000/year. Net 19,000/year. Over 25 years: 475,000 net. ROI 850%. Payback 2.6 years. Exceptional - but requires suitable water resource.

Hydropower has the best capacity factor of any renewable: 40-70% (solar 10-15%, wind 25-35%). Runs 24/7 when water flows, providing baseload generation. Main limitation: site-specific. Needs sufficient head (vertical drop) and flow rate. Environmental permits required from Environment Agency - typically 6-12 months to obtain.

Run it with sensible defaults

Using installation cost of 50,000, annual kwh generated of 60,000, electricity price per kwh of 0.3, export/fit rate per kwh of 0.05, the calculation works out to 850.00%. Nudge the inputs toward your own situation and the output recalculates instantly. The defaults are meant as a starting point, not a recommendation.

The levers in this calculation

The inputs — Installation Cost, Annual kWh Generated, Electricity Price per kWh, Export/FIT Rate per kWh, and Maintenance Annual — do not pull with equal force. 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.

How the math works

Revenue = kWh × (electricity + FIT). Net = revenue - maintenance. ROI = (net × years - install) ÷ install × 100. The working is transparent — you can verify every step yourself in the formula section below. No black box, no opaque "proprietary model".

Cost vs value in green choices

Sustainable options usually cost more upfront and less over time. This tool separates the two so the comparison is fair — looking at purchase price alone consistently makes the green option look worse than it is once lifetime costs are tallied.

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.