How to Build Your Own Small Scale Hydroelectric Generator

How to Build Your Own Small Scale Hydroelectric Generator


Building your own small scale hydroelectric generator can be a fun and rewarding project. Hydroelectricity harnesses the power of flowing water to generate electricity, providing a sustainable and renewable energy source. With some basic materials and mechanical skills, you can build a simple system to power small loads like lights, gadgets or tools.

While large hydroelectric dams require massive civil engineering projects, micro-hydro systems can generate energy from streams and small waterfalls using run-of-river designs that don't require dams or reservoirs. This makes small scale hydro a great option for remote locations, rural areas, hobbyists and homesteaders seeking energy independence.

In this guide, I will walk through the full process of designing and building a small DIY hydroelectric generator. We will cover:

Follow along to learn how to harvest the power of flowing water to build your own off-grid hydroelectric system!

Assessing Your Site's Hydropower Potential

The first step is evaluating if your stream or water source has the necessary flow rate and head to produce hydroelectricity.

Some key factors to consider when surveying your site:

Ideally look for sites with head of at least 2 feet and flow rates over 5 GPM. Sketch out the site layout and use surveying tools to measure key elevations and distances for your project calculations.

Choosing a Turbine Design

The turbine converts the kinetic energy of moving water into rotational mechanical energy. There are two main types suitable for small scale hydro:

Impulse Turbines

Impulse turbines use the velocity of water to drive the runner and do not require pressurization. Pelton wheel designs are the most common impulse turbine for micro-hydro systems.

- Can utilize high heads effectively.
- Run in open air without risk of cavitation.
- Less complex to build.

- Require very high flow velocity.
- Lower efficiency at low heads.

Reaction Turbines

Reaction turbines use pressure and velocity to drive the spinning runner. Propeller and crossflow turbines are popular examples.

- Effective at low heads and flow rates.
- Compact and simple designs.

- More complex to fabricate.
- Must be fully submerged to avoid air pockets.

Consider the head and flow rate your site can provide when choosing between impulse and reaction styles. Pelton wheels are better suited to high head sites, while propeller and crossflow turbines perform well at low heads.

Sizing Your Piping and Penstock

To deliver water to the turbine, you will need intake works, a penstock pipe, and outplow channel.

The penstock diameter is optimized based on:

Generally, larger diameters allow higher flow rates but require more materials. Use PVC, steel or HDPE piping and calculate the ideal diameter for your specific site conditions.

The intake works should include a debris filter and shutoff valve to regulate flow. The outplow is directed back into the stream past the tailrace. Consider anchoring and protecting the piping from weather and debris.

Selecting a Generator

The generator converts the rotational mechanical power from the turbine into electrical power.

Key factors for generator selection:

An AC synchronous generator with bridge rectifier to convert to DC is a common choice. But induction generators are simpler and can be more DIY friendly. Aim to match your generator's rated wattage to the expected turbine power output.

Designing the Civil Works

You will need to construct intake works, a powerhouse, and channels to integrate the hydro system:

Gravity fed water flow is preferred. Minimize the need for complex civil works like dams or reservoirs which require engineering expertise. Site selection is key for constructing simple civil works.

Integrating the Electrical System

Once your turbine produces mechanical power, the generator converts this into usable electricity. Additional components like:

Take safety precautions like grounding and housing all connections in waterproof enclosures. Size your battery bank to match your electric loads and their runtime requirements.

Construction and Testing

With your design complete, it's time to build your hydro system! Some key tips:


Constructing your own small scale hydroelectric generator is an ambitious but rewarding project. Follow the step-by-step process covered in this guide to properly assess your site, design the system components, build the civil works and integrate the mechanical and electrical elements. With patience and persistence, you can harness the renewable power of water to produce clean, off-grid electricity.

The sense of accomplishment from generating your own electricity from small streams is well worth the effort. Start planning your micro-hydro project today!