Micro-Hydro System ROI 2025/26
Calculate return on investment for a micro-hydro generation system in the UK. Enter site flow rate, head (vertical drop), turbine efficiency, system cost and Smart Export Guarantee (SEG) income to model annual generation, annual revenue and payback period.
Key Inputs
- Available flow rate in litres per second (l/s) or cubic metres per second
- Gross head (vertical drop from intake to turbine in metres)
- System efficiency (typical: 60–80% for Pelton/Turgo; 50–70% for crossflow)
- System installed cost (civil works, turbine, electrical connection, DNO notification)
- SEG export rate in pence per kWh (or deemed export assumption)
- Annual maintenance cost estimate
- Any applicable planning costs
What You'll Get
- Estimated annual generation in kWh
- Annual SEG export income
- Annual electricity self-consumption saving
- Annual maintenance cost
- Net annual income
- Simple payback period
- 20-year ROI
Important Notes — 2025/26 Rates & Caveats
Micro-hydro systems (typically 1kW–100kW) are eligible for the Smart Export Guarantee (SEG) for export to the grid (up to 5MW). Installed costs: very small systems (1–5kW) £10,000–£30,000; medium systems (5–50kW) £50,000–£200,000 including civil works, water abstraction licence and grid connection. A water abstraction licence from the Environment Agency is required for run-of-river schemes. Micro-hydro has very high capacity factors (60–80%) compared to solar or wind, making it very cost-effective per kWh generated over the system lifetime (typically 30–50 years with maintenance). Planning permission is generally required.
Frequently Asked Questions
What is the Smart Export Guarantee (SEG) rate for micro-hydro?
Micro-hydro systems up to 5MW installed capacity are eligible for the Smart Export Guarantee (SEG) in the UK. SEG requires licensed electricity suppliers with 150,000+ customers to offer an export tariff. Rates vary by supplier — in 2025/26, fixed SEG rates are typically 3–6p/kWh; Octopus Agile export can achieve 15p/kWh or more at peak periods. The installation must be MCS-certified (for systems up to 50kW) or ROO-FIT registered (above 50kW). The SEG is paid per kWh exported to the grid, measured by an export meter.
Does a micro-hydro scheme need planning permission?
Yes. Most micro-hydro schemes in the UK require planning permission from the local planning authority (LPA). In a National Park or AONB, planning scrutiny is stricter. An Environmental Impact Assessment (EIA) may be required for larger schemes. In addition, a water abstraction licence from the Environment Agency (or SEPA in Scotland) is required for any scheme abstracting more than 20m³/day. Working with an ecologist and a specialist hydro consultant early in the project significantly improves planning success rates.
How much electricity does a micro-hydro system generate?
A micro-hydro system's annual generation depends on flow rate, head and capacity factor. The theoretical formula is: Power (kW) = Head (m) × Flow (m³/s) × 9.81 × efficiency. A system with 10m head and 50 l/s flow at 65% efficiency produces approximately 3.2kW. At an 80% capacity factor (accounting for low-flow periods), annual generation is approximately 22,400kWh — enough for 6–8 average UK homes. Micro-hydro sites with consistent year-round flow and adequate head (15m+) are the most economically attractive.
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