How Much Electricity Does a Red Light Panel Use? A Hong Kong Example
A 10-minute cycle on MARS 400 uses about 0.014 kWh of electricity. At the example rate below that is roughly two cents. Here is the sum, so that you can redo it with the rate on your own bill.
The formula
Energy in kilowatt-hours (kWh) is power in watts, multiplied by hours, divided by 1,000. In Hong Kong a kilowatt-hour is the "unit" on your electricity bill. MARS 400 is specified at 82 W ±5%, and a cycle lasts 10 minutes, which is one sixth of an hour.
- 82 W × (10 ÷ 60) hours = 13.7 Wh
- 13.7 Wh ÷ 1,000 = 0.0137 kWh
An example in HK dollars
Electricity prices differ by supplier, by area and by how much you use, so the rate below is an example, not a quote. Suppose your rate is HK$1.50 per unit:
- One cycle: 0.0137 kWh × HK$1.50 = about HK$0.02.
- Five cycles a week, about 22 a month: 0.30 kWh, about HK$0.45.
- Even at twice that rate, five cycles a week stay under HK$1 a month.
Where to find your own rate
Your bill from CLP Power or HK Electric shows the charge per unit, and the websites of both companies list their current tariffs. Rates change, so use the one on your latest bill.
Quick answers
Does the mode change the electricity used?
The specification gives one power figure, 82 W ±5%, so this sum uses it for every mode.
How can I measure the real draw?
A plug-in energy meter between the socket and the adapter shows the real draw in watts and the energy used over time.
A few caveats
- The 82 W figure is the nominal power. The real draw can vary a little with the mode and with the ±5% tolerance.
- The power adapter may draw a small amount while it is plugged in and the panel is off, so unplug it if you will not use the panel for a while.
- This is only the cost of electricity. It says nothing about results, and we make no promise about them.
See MARS 400 for the specifications used in this sum.
