"My electricity bill suddenly increased by R 500 compared to last month!" This was a recent message from my friend who started legally growing cannabis in Cape Town.
In South Africa, following the 2018 legalization of personal use and cultivation of cannabis, more and more growers have found that electricity has become one of their largest operating costs.
Plant grow lights play a central role in indoor cannabis cultivation, directly affecting yield quality and economic benefits.
In recent years, full spectrum LED grow lights have become increasingly popular among South African cannabis growers, gradually replacing traditional high-pressure sodium lamps.
But a key question still troubles many South African growers: What is the real power cost of using plant grow lights to grow cannabis in South Africa? What cost optimization strategies are suitable for South Africa's unique environment?
This guide, combined with local South African conditions and experienced grower insights, will help you understand and optimize grow light power consumption in the South African environment. whether you're a small grower who just obtained a personal use permit or a team planning to build commercial facilities.
Letโs read on.
Calculating the cost of running a grow light
When it comes to calculating electricity bills, many people get confused. But don't worry, it's not complicated.
We just need to understand three key factors: your grow light's actual power, how long it runs each day, and the specific electricity prices in various South African regions. With these three pieces of data, calculating monthly electricity bills is as simple as 1+1=2.
1.Determine grow light wattage
For the actual power of plant grow lights, the simplest method is to check the "actual power consumption" in the product manual. If you can't find it, invest in a socket power meter (about R 200-300 at mainstream South African electronics stores) for the most accurate measurement.
2.Determine the running time and period
When it comes to cannabis cultivation light time, different growth stages have vastly different requirements. This point cannot be overlooked, as it not only relates to electricity bills but also directly affects yield and quality.
- Vegetative period: 18 hours of light/day (typically lasting 3-8 weeks, depending on the strain)
- Flowering period: Precisely 12 hours of light/day (typically lasting 8-11 weeks)
So when calculating electricity bills, don't forget to consider the differences in lighting time at different stages. For example, a lamp using 6 more hours of electricity daily during the vegetative period will naturally cost 50% more.
The calculation formula is simple:
Daily power consumption (kWh) = Grow light power (kW) ร Operating time (hours)
If your light is 450W (0.45kW) and runs for 18 hours per day, it will consume 0.45 ร 18 = 8.1kWh of electricity daily.
3.Use the cost per KW hours from your electricity supplier
South African electricity prices are not constant, with variations by region and time period, not to mention the annually increasing base rates.
According to the latest data from the National Energy Regulator of South Africa (NERSA), the standard residential electricity price from April 2025 is 3.712 R/kWh. Commercial electricity is 1.795 R/kWh.
A grower in Pretoria shared his electricity-saving tip: "I schedule most of my lighting time from 9 PM to 9 AM the next day because South African nighttime electricity prices can be more than 25% cheaper." This is a real money-saving technique!
The calculation formula is as follows:
Daily electricity cost (rand) = Daily power consumption (kWh) ร Electricity cost per kilowatt-hour (R/kWh) Monthly electricity cost (R) = Daily electricity cost (R) ร 30 days
Next, let's look at a real case, which is much more intuitive than dry theory.
Scenario : 800W LED Grow Light
John is an amateur grower in Cape Town who uses an 800W LED grow light (actual measured power consumption 800W) to grow 9 cannabis plants. This power of 800W LED Grow Light covers approximately 3 square meters, just meeting the needs of his small grow room.
John's plants are in the vegetative stage, receiving 18 hours of light daily. His electricity cost calculation is as follows:
Daily power consumption = 0.8kW ร 18 hours = 14.4kWh Daily electricity cost = 14.4kWh ร 3.712 rand/kWh = 53.45 R Monthly electricity cost = R 53.45 ร 30 days = R 1,603.5ย
John is smart; he utilizes Cape Town's time-of-use electricity pricing policy, scheduling 16 hours of lighting during off-peak periods: Optimized monthly cost โ R 1,603.5 ร 80% = R 1282.8ย
"The saved 400+ rand is enough for me to add some new growing supplies each month," John happily says. "Electricity optimization is a small investment with big returns."
If you are a commercial user, the electricity price will be even cheaper. Still using the 800W example: Commercial user calculation = 0.8kW * 18 hours = 14.4kWh * 1.795 R/kWh = R 25.85ย * 30 days = R 775.44ย * 80% =R 620.35ย
A commercial user needs only 620 R per month at most, and electricity costs during the flowering period will be even cheaper, needing lights on for only 12 hours, saving approximately 25% on electricity costs.
However, each city has different electricity prices with some variations. The specific electricity price depends on the calculation method of the local city. Below is for reference:
- Cape Town: Average 2.35-2.80 R/kWh
- Johannesburg: Average 2.50-3.70 R/kWh
- Durban: Average 2.40-2.95 R/kWh
- Pretoria: Average 2.55-3.15 R/kWh
For South African growers curious about how long it takes for cannabis to grow, it's approximately 3-5 months, depending on the cannabis strain and cultivation method.
Tips for Optimizing Electricity Usage
Considering South Africa's special electricity environment and high electricity prices, I've collected some innovative strategies used by local South African growers that are particularly suitable for the South African environment.
1.Choose efficient LED fixtures suitable for the South African environment
- Photon efficiency ratio is key: A cultivation consultant in Cape Town emphasizes: "In South Africa, Plant Grow Lights with high photon efficiency ratios should be prioritized. Look for fixtures that output at least 2.6ฮผmol/J per watt.
TheOneGrow is a grow lights South Africa brand, and their lamps typically have a light efficiency ranging from 2.6 to 2.9 ฮผmol/J, which can provide 30-50% more effective light under the same electricity cost.
- Advantages of South African local brands: Choose some merchants with after-sales service in South Africa, so if there are any problems with the lights, they can be resolved promptly.
- Remote dimming systems: A cannabis grower in Durban shares: "I invested in adjustable brightness dimming controllers, now I can directly control the brightness of plant grow lights at home, and also control fan speed, making things much easier."
Utilize South Africa's abundant sunlight resources
An innovative grower in the Eastern Cape designed a unique system: "I designed my grow room with controllable transparent skylights at the top.
During South Africa's bright daytime (over 300 sunny days per year), I mainly use natural sunlight, only using LED supplementary lighting in the early morning and evening, saving about 40% electricity daily."
South Africa-specific electricity cost optimization techniques
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Time-of-use electricity price advantages: A commercial grower in Johannesburg discovered: "Some areas in South Africa offer time-of-use pricing plans, with nighttime rates potentially more than 50% lower than peak periods.
Scheduling lighting from 8 PM to 7 AM means 80% of electricity use occurs during low-rate periods."
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Commercial vs. residential electricity price analysis: An economist and grower in Durban conducted a detailed analysis: "In South Africa, once your monthly electricity usage exceeds 900 kilowatt-hours, applying for a small commercial electricity connection becomes more economical.
Despite higher basic fees, the unit price is lower, saving 20-30% for large growing facilities."
Conclusion
Plant grow lights play an important role in improving crop yield and quality but also increase electricity costs.
By reasonably choosing grow light power, optimizing operating times, utilizing natural light, and adopting energy-saving measures, you can effectively reduce electricity expenditure and achieve efficient, sustainable cultivation.
Contact us to learn more about energy-saving solutions and help your cultivation business move toward a more efficient, more environmentally friendly future!
FAQs
Q1:How much electric does a grow light use?
A 600W LED grow light in Cape Town running 18 hours daily consumes ~324 kWh/month. At Eskom's residential rate (R2.85/kWh + 15% VAT), monthly costs reach R1,100. For 1000W lights, usage jumps to 540 kWh/month, costing ~R1,800.
Q2:Is it better to leave grow lights on all the time?
No. Cannabis needs 18-24 hours of light during the growing phase, but only 12 hours during the flowering phase. Too much light is not a good thing for cannabis, and the plant also needs to experience the regulation of night and day.
Q3:What is the disadvantage of grow light?
The relative disadvantage of LED plant growth lights is the high cost. Other aspects such as energy saving and heat dissipation are better than HPS lights, and the life span can reach 50,000 hours.
Q4:Will LED lights raise the electric bill?
As long as you use Plant Grow Lights the monthly electricity bill will increase relatively. However, compared with HPS lamps, 800w led grow light can save 40% energy. For example: 800W HPS lamp costs 2,200 rand per month, while grow lights costs 1280 rand per month.