What Size Landscape Lighting Transformer to Use – Light Up Your Nighttime Oasis

landscape lighting transformer

Knowing how much power your landscape lighting system uses is important because it allows you to estimate the total cost of operating the fixtures. This is very helpful for determining whether or not a new landscape lighting system will be able to pay for itself over its lifetime, and in some cases may even reduce your property taxes.

It can also help you choose which types of fixtures use less energy than others if you’re looking into shopping around for more efficient options.

To start this article off, we’ll go through a couple of easy steps that will give you an idea of what type of landscape lights are drawing how much wattage from your home’s electrical outlet(s). It’s important to keep in mind though that these numbers aren’t entirely accurate and should only be used as a rough estimate.

Collect Information About Your Lights

Landscape Lighting

The first thing you’ll need to know is how much wattage your fixtures are pulling from the wall before they start shining their light. This information can usually be found by looking at the back of each fixture or by searching online for information on your specific lights.

If this isn’t possible or if you want to get an idea about what ballpark you’re in, most modern landscape lighting systems draw anywhere between 100 and 500 watts before they begin lighting up.

The main factor that affects how much power the lights use is not actually related to the number of watts used but instead how much voltage it draws. Voltage can change even though the amount of power stays constant because different types of bulbs draw different amounts of power at different voltages.

For example, a typical landscape light that is rated for 100 watts and 120 volts would actually only use 80 watts if it is halogen instead of LED.

Calculate the Average Wattage Used per Fixture

To figure out the average wattage used by your system, take the number of fixtures you have and multiply them by their wattage rating (before shining their light). Then divide this number by 1000.

An easy way to do this with odd numbers is to round up and then divide them in half, which will give you a very accurate estimation. So if you have 24 lights that are each drawing 300 watts before shining their light, you would divide 600 (24 lights x 300 watts) by 1000 to get an average of 0.6 amps per fixture.

Calculate the Total Amperage Used by Lights

Now that you have the number of fixtures and the average wattage used per fixture, you can easily calculate how many amps your landscape lighting system is drawing from the outlet(s). This will help give a rough estimate on why your electricity bill has gone up in the past month or so.

To do this, multiply your total number of fixtures by their average wattage used per fixture and then add together these numbers for every set of outlets in your home. Then multiply this number by 1.1 to compensate for other appliances that might be on the same circuit as your landscape lights.

An example would be if you had 24 fixtures that used 0.6 amps per fixture and were plugged in to two separate outlets, you would multiply 24 x 0.6 + 24 x 0.6 = 55.2 + 55.2 = 111 amps.

Calculate the Total Kilowatts Used by Lights

To calculate the total amount of energy used by your lights, multiply your average wattage per fixture by the number of hours they are left on each day. For most residential homes this will usually mean leaving them lit for around 6-10 hours each night depending on what time you get home from work. The last thing you need to do is multiply the total kilowatt-hours per day by 365 days in a year. This will give you the total number of kWh used by your landscape lighting system per year.

An example would be if you had 24 lights that each used an average of 0.6 watts per hour and they were on for 10 hours every night for 300 days, you would multiply 24 x 10 x 300 = 72,000 watts x 1000 to get 719,600-watt-hours per year.

Calculate Your Annual Cost per Kilowatt Hour

This step won’t always be possible but if it is available to you then use it because it is a very easy way to calculate how much your lighting system will cost you per year. All you need for this is the nameplate rating on your transformer

These numbers are usually something like 115/120, 208/220, or 347/360 and then either “V” or “V-ph-Hz”. This information can be found on the side of most transformers and is generally located near where the power cord meets the box itself.

Once you have this number (which should be in volts), multiply it by the total amps used by lights (found above) and divide this product by 1000. Then multiply that result by your kWh per year number (found above). This will give the estimated amount of money spent by your landscape lighting system per year.

An example would be if you lived in a home that used 347/360 volts and had 24 lights that each used 0.6 amp per hour for 10 hours a night 300 days a year, then your estimated cost per kWh would be 347 x 0.6 + 347 x 0.6 = 307 + 614 = 1011 amps x 1000 to get 1,011,000 watts x 365 to get 365,825,000 watt hours / 1000 to get 365,825 kWh x $0.10 (average) = $36,582 .25 (annual cost)

Factors Affecting Energy Consumption

Low Voltage Transformer

There are several factors that can influence the energy consumption of a landscape lighting system. Understanding these factors can help you make informed decisions when designing, installing, and maintaining your landscape lighting to minimize energy costs.

  1. Type of Bulbs: Different types of bulbs have varying levels of energy efficiency. LED bulbs are the most energy-efficient option available, consuming up to 80% less energy than incandescent bulbs and 30-50% less than halogen bulbs. Compact fluorescent bulbs (CFLs) also consume less energy than incandescent and halogen bulbs but are not as efficient as LEDs.
  2. Transformer Efficiency: The efficiency of the transformer used in your landscape lighting system can impact energy consumption. High-quality, energy-efficient transformers are available and can help reduce energy loss during the voltage conversion process.
  3. Lighting Design: The overall design and layout of your landscape lighting system can influence energy consumption. Proper placement of lights, using the right number of fixtures, and choosing the correct beam angles can help maximize lighting efficiency.
  4. Lighting Controls: The use of lighting controls, such as timers, dimmers, and motion sensors, can help minimize energy consumption by ensuring that lights are only on when needed.
  5. Maintenance: Regular maintenance of your landscape lighting system, including cleaning fixtures and replacing burnt-out bulbs, can help maintain energy efficiency.

Tips for Reducing Energy Consumption

Here are some practical tips for reducing energy consumption in your landscape lighting system:

  1. Choose Energy-Efficient Bulbs: Replace incandescent and halogen bulbs with energy-efficient LED bulbs. LEDs have a longer lifespan and consume significantly less energy, which can result in significant energy savings over time.
  2. Install Lighting Controls: Incorporate timers, dimmers, or motion sensors to control your landscape lighting. This will help ensure that lights are only on when necessary, reducing energy waste.
  3. Optimize Lighting Design: Carefully plan your landscape lighting layout to minimize the number of fixtures needed to achieve the desired effect. This can include using lights with adjustable beam angles or opting for fixtures that can illuminate multiple areas.
  4. Upgrade Your Transformer: Invest in a high-quality, energy-efficient transformer to reduce energy loss during the voltage conversion process.
  5. Perform Regular Maintenance: Keep your landscape lighting system in good working order by cleaning fixtures, trimming overgrown foliage, and replacing burnt-out bulbs promptly.

The Environmental Impact of Landscape Lighting

Landscape Lightings

Landscape lighting can have several environmental impacts, some of which are negative. By understanding these impacts, you can make responsible choices in your landscape lighting design and operation to minimize harm to the environment.

    1. Energy Consumption: Landscape lighting contributes to overall energy consumption, which can lead to increased greenhouse gas emissions if the electricity used is generated from fossil fuels. Choosing energy-efficient bulbs and using lighting controls can help minimize energy consumption.
    2. Light Pollution: Excessive outdoor lighting can contribute to light pollution, which has negative effects on human health, wildlife behavior, and the visibility of the night sky. To reduce light pollution, use shielded fixtures that direct light downward, and avoid over-illuminating areas.
    3. Wildlife Disruption: Artificial lighting can disrupt the natural behaviors and habits of nocturnal wildlife, such as birds, insects, and mammals. To minimize disruptions, choose lighting with warmer color temperatures (2700K-3000K), and avoid using excessively bright lights or lighting natural habitats unnecessarily.
    4. Resource Use: The manufacturing, transportation, and disposal of landscape lighting components, such as bulbs and fixtures, can contribute to resource depletion and environmental pollution. Choosing durable, energy-efficient components can help reduce the environmental impact of your landscape lighting system.


How does landscape lighting affect my energy bill?

Landscape lighting can have a significant impact on your energy bill, especially if you have a large number of fixtures or if they are on for long periods of time. The energy consumption of your landscape lighting system depends on several factors, such as the type and wattage of bulbs, the number of fixtures, and the length of time they are on. By calculating your average wattage per fixture and the total number of fixtures, you can estimate the total amount of energy used by your system and determine its impact on your energy bill.

What factors affect the energy consumption of landscape lighting?

Several factors can affect the energy consumption of your landscape lighting system, including the type and wattage of bulbs, the number of fixtures, the length of time they are on, and the voltage of your system. LED bulbs, for example, use less energy than halogen bulbs and have a longer lifespan, making them a more energy-efficient choice. Additionally, using fewer fixtures or turning them off when not in use can significantly reduce energy consumption.

How can I reduce the energy consumption of my landscape lighting?

There are several ways to reduce the energy consumption of your landscape lighting, such as using LED bulbs, reducing the number of fixtures, and installing a timer or motion sensor to control when the lights are on. You can also consider using solar-powered lights, which do not require electricity and are environmentally friendly.

What is the environmental impact of landscape lighting?

Landscape lighting can have both positive and negative environmental impacts. On one hand, it can enhance the beauty and safety of outdoor spaces, increase property value, and promote outdoor activities. On the other hand, it can also contribute to light pollution, disrupt natural ecosystems and wildlife, and increase energy consumption and greenhouse gas emissions. Therefore, it is important to use energy-efficient bulbs, install fixtures in strategic locations, and limit the amount of time they are on to minimize the environmental impact of your landscape lighting.

How can I choose energy-efficient landscape lighting fixtures?

To choose energy-efficient landscape lighting fixtures, you can look for bulbs with lower wattage and longer lifespans, such as LED bulbs. You can also choose fixtures made with eco-friendly materials and designed for minimal light pollution. Additionally, you can consult with a professional landscaper or lighting designer to help you select the most energy-efficient and environmentally friendly options for your specific needs and preferences.


Remember that this is only an estimation and there are other factors that can alter your annual cost per kWh. If you know the actual nameplate rating on your transformer, for example, you could use a different equation to get even more accurate results. Also, keep in mind the prices of your utility company.

An important thing to remember when reading this article is that every home, climate, landscape light setup, and electrical system is different so it’s going to be impossible to calculate exactly how much power your lights use unless you have a meter installed or a clamp-type ammeter handy.

There are many things that do not get taken into consideration when using these equations such as how many fixtures are on a given circuit, the actual wattage of your lights, temperature, etc.