Beyond solar
Solar is the most common homestead power source because it suits almost every site. But it has a weakness: winter and cloudy weather.
Two other sources can fill that gap on the right land:
- Small wind: a turbine on a tower turns wind into electricity.
- Micro-hydro: a small turbine turns flowing water into electricity. The DOE uses the term for systems up to about 100 kW.
Both depend on the site far more than solar does. The first job is always to measure what the site has.
Small wind needs strong, smooth wind
The energy in wind rises very fast with speed. Doubling the wind speed gives about eight times the power. So a site with slightly stronger wind can make far more energy.
DOE’s small wind guide suggests an average yearly wind speed of at least about 9 mph (4 m/s) for an off-grid system. For a system tied to the grid, it suggests about 10 mph (4.5 m/s). Many homestead sites, especially wooded or sheltered ones, fall short.
Wind near the ground is slow and choppy because trees and buildings get in the way. DOE’s rule of thumb is to put the bottom of the blades at least 30 feet (9 m) above anything within about 300 to 500 feet (90 to 150 m). That often means a tall tower.
Text description
A side view, not to scale. On the left, trees and a house break up the wind near the ground, making it slow and choppy, shown by wavy arrows. Higher up, the wind is smoother and faster, shown by straight arrows. On the right, a small wind turbine stands on a tall tower. A dashed line marks the top of the tallest obstacle nearby. The bottom of the turbine blades is at least 30 feet (9 meters) above that line, for anything within about 300 to 500 feet (90 to 150 meters) of the tower, following the DOE rule of thumb. A note says tower design and raising need a structural engineer and an experienced installer.
Micro-hydro needs head and flow
Micro-hydro depends on two things:
- Head: the vertical drop from where water enters the pipe to the turbine. More drop means more pressure. Net head is what is left after friction in the pipe. DOE suggests taking off 5 to 10 percent for a first estimate.
- Flow: how much water passes, in gallons per minute (gpm) or liters per second.
DOE gives a rough rule for small systems: net head (ft) × flow (gpm) ÷ 10 ≈ watts. Dividing by 10 roughly allows for losses in the turbine and generator. A stream with 100 feet of net head and 20 gpm gives roughly 200 W, all day and night.
That is small, but it runs 24 hours. 200 W around the clock is about 4.8 kWh a day, more than many solar arrays make in midwinter.
Text description
A side view of a hillside, not to scale. At the top, an intake takes water from a stream. A pipe carries it down the slope to a small turbine house at the bottom, and the water then returns to the stream. Head is the vertical drop from the intake to the turbine; net head is what is left after friction in the pipe, about 5 to 10 percent less for a first estimate. Flow is how much water passes, in gallons per minute. A box gives the DOE rule of thumb for small systems: net head in feet times flow in gallons per minute, divided by 10, is roughly the watts. Example: 100 feet times 20 gallons per minute, divided by 10, is about 200 watts, all day and night, about 4.8 kilowatt-hours a day.
Why steady beats strong
Solar makes power only by day. Micro-hydro can run day and night, every day the stream flows. A small, steady source often does more for a battery than a large, intermittent one.
Wind and hydro also tend to peak in different seasons from solar. In many places, wind is stronger in winter, and streams run higher in winter and spring. Pairing them with solar can shrink the winter gap.
Text description
A chart of relative output by month, a common pattern rather than data for any one site. Solar output is low in winter, rises through spring and peaks in June and July. Wind is often strongest from late fall through early spring and weakest in summer. Stream flow for micro-hydro often peaks in spring, stays fair in winter, and drops in late summer and early fall; streams can also freeze. A shaded winter band shows where wind and hydro can fill in for solar.
But streams drop in dry summers and can freeze, and wind comes and goes. Neither replaces a battery.
Sources compared
Which source fits the site
Which source is worth a closer look on each site?
- A flat, wooded lot with a clear sunny clearing
- A spring-fed stream on a steep hillside
- A sunny, open south slope in a sheltered valley
- A coastal bluff with high average wind speed
- A year-round creek drops 80 feet across your land
- An open ridge with steady strong winds and no trees for miles
Measure before you buy
Do not guess. Measure.
- For wind, use DOE wind maps as a first look, then measure wind at your site for a year if you can. Hilltops and gaps can be very different from maps.
- For hydro, measure flow in the dry season, not just in spring. Measure head with a survey tool or a long hose and a pressure gauge, or hire someone to survey it.
Ask your county about tower height limits and setbacks, and your state about water rights before using a stream.
Pro and permit
Check
A stream gives 50 feet of net head and 40 gpm in the dry season. Using the DOE rule of thumb, about how much power could a micro-hydro system make?
Summary
- Small wind needs strong, open wind and a tall tower. Average wind of at least about 9 mph is a common starting bar for off-grid use.
- Micro-hydro needs head and flow. Net head × flow ÷ 10 gives rough watts.
- Steady sources pair well with solar and can shrink the winter gap.
- Measure the site first. Towers, wiring and water rights need professionals and permits.
Go deeper: the cube of wind speed
The power in wind rises with the cube of its speed. If wind speed goes from 10 to 12 mph, a 20 percent rise, the power goes up by about 73 percent. This is why small differences between sites, and between tower heights, matter so much. It is also why average wind speed alone can mislead: a site with steady 10 mph wind and a site with calm days and gusty storms can share an average but give very different energy.