Can I get by with only solar in my motorhome?
The short answer is yes, but it depends on your expected usage. We run entirely on solar even with an electric fridge, computer, microwave etc., but then we've got a very large system. Our rig has 8 x 64w panels which is OK in summer/hot areas but often not enough down south and/or in the winter so we sometimes run a generator as a backup.

We recently added two 120w panels, they live on the Landcruiser roof and can be used for the 'cruiser batteries, or plugged into the motorhome.

We're carefull about our power consumption but don't skimp on the use of appliances. However if you are prepared to be more frugal you can easily live without a generator and with a smaller system.

How much will a solar system cost?
Of course it depends on the size so let's look at the two extemes.

• small system - 1 panel, 1 battery, simple regulator, small inverter. About $1,500.
• large system - 8 panels, 8 batteries, smart regulator, large inverter. About $15,000.

How fast can I charge my house batteries?
As a rule of thumb, at one tenth their rating. For example if you have a 500ah battery bank you can charge it at 50 amps.

What this means is that you cannot simply put a massive generator in the rig to charge the batteries in 5 minutes.

How much of a battery's capacity can I use?
As I understand it a normal deep cycle battery should not be discharged to more than 50% of its rating but keeping it above 80% is preferred. Discharging too much and too many times will damage the battery. What this means is that your 100ah battery is really just a 20ah battery.

The newer AGM batteries do not have this limitation. They can apparently sustain hundreds (even thousands) of deep discharges without failure.

Is it worth the effort to tilt the solar panels to the optimal angle?
No, the extra hardware required to allow the panels to tilt is probably not worth the extra current achieved by having the panels perpendicular to the sun's rays.

Once again though you should think about your lifestyle. If you spend a lot of time in the South and/or winter months the sun will have a much lower angle and tilting the panels becomes more reasonable.

However mosty people buy a motorhome to spend more time in the warmer northern climates. The sun is much higher in the sky as you approach the tropics so there is even less argument for tilting.

Having said that, tilting and rotating does make quite a difference, it's just that normally the hardware involved is normally too difficult to implement.

What about a removable panel so I can park in the shade?
This is a common technique used by four wheel drivers and owners of smaller campers. It's fair enough as a method of increasing the efficiency of one or two panels and we do just that with the Landcruiser, but there is always the risk of theft.

Larger rigs can usually have several panels so I think this technique is not practical for them.

When calculating usage how many hours of sunlight should I assume?
The industry standard is about 5 hours per day. This is probably too little for summer in Kakadu and too much for a winter's day in Tasmania.

For example in Perth you will get nearly 8 hours in January. While in Launceston, if you blink you'll miss the 2.5 hours of sunlight available in June.

One anomaly is that most far north locations get more sunlight in winter, presumably because of the high amount of cloud during the wet season. This may be a good argument for using the new Unisol broad-spectrum panels that are supposed to be more efficient in overcast conditions.

Can I run air conditioning from a solar system?
Yes, but not for very long. If you have a large enough invertor you could run the air conditioner for a short while but they use far too much power (about 1500-3000w) to be run from batteries for long.

Naturally this depends on the size of your battery bank but to give you an idea--using a very large battery bank of 8 185ah batteries weighing in at about 400kgs, and assuming a max allowable 20% discharge, you could run the airconditioner for about 1-2 hours. That's not counting your other appliances.

In short, if you intend to bush camp then be prepared to run the generator or go without airconditioning.