Founder | BPI® Energy Auditor Certified Professional
Small wind turbines are becoming more popular as people look for ways to reduce their energy costs and become more environmentally friendly.
But how do you know if a small wind turbine will be enough to power your home?
This article will give you the tools to calculate how much power you need for your home. We will also include an example calculation and a way to determine whether installing a wind turbine is worth it.
Can a Small Wind Turbine Power Your Home? (How To Calculate)
A 5kW small wind turbine is enough to power a typical US home that needs about 900kWh per month. This figure assumes you have average wind speeds of at least 12mph (19 kph constantly), good site conditions, and a good-size diameter rotor.
How To Calculate the Amount of Power Your House Needs
To calculate the total power required to run your home, you must add the wattage of each appliance and device you use. Many devices will have this information on a label on the back or bottom. You can look it up online or in the owner’s manual if you can’t find it.
For example, let’s say you have the following appliances and tools:
- Coffeemaker: 1,000 watts
- Microwave oven: 1,200 watts
- Fridge: 1,200 watts
- Dishwasher: 1,800 watts
- Washing machine: 750 watts
- Clothes dryer: 1,500 watts
- Laptop: 60 watts
- TV: 100 watts
- Other devices: 1000 watts
In this case, the total wattage you need is 1,000 + 1,200 + 1,200 + 1,800 + 750 + 1,500 + 60 + 100 + 1000 = 8,610 watts/hour.
Multiply this by the hours you need to keep the appliances running. For this example, let’s use 8,610 watts to keep things simple.
Now that you know the total wattage you need, you can calculate the power your small wind turbine should generate.
To do this, you need to know the following information:
- The average wind speed in your area
- The rotor diameter of your turbine
- The efficiency of your turbine
You can find the average wind speed for your area on the National Renewable Energy Laboratory’s (NREL) website.
The rotor diameter is the distance from one edge of the blades to the other. The efficiency of a turbine refers to how well it converts the wind’s energy into electricity. You can find this information in the product specifications for your turbine.
For example, let’s say you have an average wind speed of 12m/s, and your turbine has the following specifications:
- Cut in speed: 9 m/s
- Air density: 1.225kg/m3
- Rotor diameter: 15 feet
Now you can plug this information into the formula to calculate the power output of your turbine.
P = [air density] • [swept area] • [wind speed cubed] • 0.5
The air density is 1.225 kg/m^3. The swept area is the rotor diameter squared multiplied by 3.14. The wind speed is measured in meters per second.
This is how that looks in an equation:
P = 1.225 • (3.14 • 7.5^2) • 12 • 0.5
P = 1,298 watts
Using this example, your small wind turbine should generate at least 1,298 watts of power per hour. A 5kWh turbine with at least 30% efficiency is ideal for this task.
Things To Keep in Mind When Shopping for a Wind Turbine
It is important to note that wind turbines are not 100% efficient. This caveat means that a 1kWh turbine will never generate 1,000 watts. The average efficiency of a small wind turbine is 20-35%. So, a 1kWh turbine will generate 200-350 watts of power on average.
Homeowners often opt for 5kW small wind turbines when they only need 1kW of power. This gives them a buffer to generate enough electricity even when the wind isn’t blowing as hard as usual. It is also important to remember that the power output depends on the wind speed. A turbine will generate more energy in a gusty wind than in a light breeze.
The power output of a turbine decreases as the wind speed increases. This is because the blades are designed to spin at a certain speed to generate power. When the wind speed goes above this, the blades activate a braking mechanism, and the turbine produces less power.
Choosing a small wind turbine with a high wind speed rating is crucial to your success. A powerful turbine with a higher wind speed rating can generate more power in high winds.
The direction of the wind is another significant factor. A turbine will generate more power if the wind blows directly into the blades. On the other hand, if it blows at an angle, the turbine will not spin as well.
Horizontal vs. Vertical Axis: Which One Should You Get?
There are two primary types of small wind turbines—horizontal axis and vertical axis.
Horizontal axis turbines are the go-to option for most people because they are more efficient. You will have to pay more for this increased efficiency, but the extra money is generally worth it. Vertical axis turbines are quieter, making them excellent for residential areas.
There are pros and cons to each type of turbine.
Horizontal axis turbines can generate more power.They are also easier to maintain because all the parts are easily accessible. However, they also make more noise and are more expensive.
Vertical axis turbines are less efficient and don’t generate as much power. They are also harder to maintain because the parts are not as easily accessible. However, they make less noise and are less expensive.
That makes vertical axis small wind turbines perfect for residential applications where noise is a concern. Many people also like the fact that they are less expensive.
Other Components You Need To Run a Wind Turbine
In addition to the turbine itself, you also need a tower, batteries, and a charge controller.
- The tower – you must raise the turbine high enough to catch the unobstructed wind. The higher you go, the more power the turbine will generate. Turbine makers recommend towers as tall as 100 feet (30 meters). The issue with these tall towers is that they are expensive and require a lot of concrete for the foundation.
- Batteries – these are needed to store the turbine’s power. Most experts recommend getting lithium-ion batteries because they are the most efficient. These juice packs can be expensive, but they will last longer and perform better than lead-acid batteries.
- The charge controller – this part is used to regulate the power coming from the turbine before it gets to the batteries. It prevents overcharging the juice pack, which is the leading cause of battery damage. The charge controller also prevents too much battery discharge, which is detrimental to your batteries.
- Inverter – this component converts the DC power from the batteries into AC power, the type of current that your home uses. Most homes will need a 3000-watt inverter.
Wind Turbine Maintenance Costs
Like most machines, your small wind turbine need to be serviced and repaired to keep its efficiency. Here are the most important things to look out for:
- The generator must be maintained regularly – the main maintenance cost for your generator is usually the blades. You must replace them every few years because they wear out from the wind and weather. Blade replacement can cost anywhere from $500-$2000 per blade.
- Maintenance of the tower – towers need to be inspected and repaired regularly. This is because they are constantly exposed to the elements. Tower inspection and repair can cost anywhere from $1000 to $5000 per year.
- Maintenance of the batteries – batteries need to be replaced every few years as well. These parts cost anywhere from $500-$3000.
Small Wind Turbine Return on Investment
A small wind turbine’s average return on investment (ROI) is around 10%. If you invest $1000 in a turbine, you can expect to make $100 annually. This is not a great ROI, but it is better than what you would get from most savings accounts.
The main reason the ROI for turbines is not so great is partly because of the high upfront cost. The turbine itself can cost anywhere from $5,000-$20,000, meaning it can take a long time to recoup your investment.
Another reason why the ROI for turbines is not higher is maintenance costs. As we saw earlier, blades and batteries need to be replaced every few years, and you must also service the moving parts. These costs can add up over time and eat into your profits.
We have a cousin who has a small wind turbine. He has had it for three years and says it has been a good investment. He has not had to replace the batteries yet, but he has had to replace the blades twice. He says that his turbine generates enough power to run his entire house and then some. His only complaint is the noise.
The Bottom Line
Now you know how to calculate the turbine size you need to power your home. The main thing to remember is that you need to have enough space for the turbine and the tower. You also need to factor in the maintenance costs and the return on investment (ROI).
So, if you are considering getting a small wind turbine, we say go for it. Just make sure to do your homework first.