Newsletter Archive

January Specials

For this month we are offering 5% off our whole range of automotive cable. Now is a good time to check that your cables are the correct size. There is a cable-sizing chart on our FAQ page – go to Energy from Nature (extracts from the book), then to Cable Sizing and Voltage Drop.

We are also pleased to offer a range of great specials of some selected Selectronic inverters. Check out these high quality Australian-made inverters for great value. All models over 1000W come with a full 5-year warranty!

Laptop Computer Power Consumption

Laptop computers are becoming a lot cheaper and are a good choice for those wishing to run a computer for extended periods on a solar system. I can now give you several laptop power consumptions thanks to Rob, Dave and Ernie from the Yahoo Discussion Group called “12VDC_Power”, and to Peter Pedals and Chris Nuss from our staff.

1. Sony laptop 3 years old: 28 Watts (W)

2. Dell Inspiron 600M, 40GB drive, 512 MB Ram; 14.5 inch display: 23-25 Watts (40-53W if charging the internal battery).

3. IBM Think Pad: 30 Watts

4. Toshiba: 25 Watts

5. Mac 1 Book 2001: 30 Watts

6. Compaq Presario 700, 20GB drive, 14.5 inch monitor: 28 Watts when running; 40-60 Watts booting up and shutting down; 2.3 Watts on standby.

From this list of measured laptop computer power consumptions, I’d suggest 25-30W is the average range. These power consumptions are measured on the AC side (eg, they do not include inverter losses).

A small number of laptops are designed to work direct off a 12 Volt battery. The vast majority run from 14-20 Volts DC.

Generally there are two options to run your laptop from your solar system – an inverter (such as our 150W X-Power Inverter – INV-014) or from a DC-DC voltage up-converter (APX-010). While we have not extensively tested these two options, it is our feeling that the up-converter would be in the order of 15% more efficient than a small inverter. Running the laptop on its own on a large house inverter may not be very efficient.

To conclude, we’d suggest that a laptop computer would use around 30W off the DC power supply, and say 40-50W after inverter losses. An 80 watt solar panel should easily run a laptop computer all day in say the Brisbane area. A previous article (in our FAQ section) found that most desktop computers will use around 120-140 watts before inverter losses. This depends a bit on the size and type of monitor and how hard the computer is working. Newer desktops with the faster processors may average out to about 200W, unless you have a LCD monitor. An 80 watt solar panel will, on average, only run the desktop computer for a 1-2 hours. So if you are planning on using a computer for say 8 hours a day on a solar system, a laptop could save you purchasing about three to four 80 watt solar panels, 300Ah of increased battery storage, and a larger inverter!

Have a happy new year!