Newsletter Archive

E-News Issue #79

5 January 2005

January Specials

We have two specials for you this month. You can always access these monthly specials by clicking on the Special Icon on our website.

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 (extract from our book Energy from Nature) on our Cables & Fuses FAQ page.

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

Using a Laptop Computer on a Solar System

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, Iā€™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 ā€“ an inverter (such as our 150W X-Power Inverter ā€“ 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!

Cheers from Dave and all the RPC crew.

Dave Lambert (Director)

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We install solar systems in Northern NSW and Southern QLD.


QLD:
Gold Coast (from Coolangatta to Southport), Nerang and Hinterland (Beaudesert) and out West (Warwick, Stanthorpe, Killarney)


NSW:
Northern NSW (Tweed Heads to Yamba, including Evans Head, Byron Bay and Ballina); the Far North Coast Hinterland (Grafton via Lismore to Murwillumbah) and out West (Casino to Tenterfield, including Drake and Tabulam, as well as Woodenbong and Bonalbo)

For larger system we also go up to Brisbane or down to Coffs Harbour and even Glen Innes. Other places by arrangement.