What electricity we are not using in our own home, you might be using. We have provided about $73 worth of electricity in the first month to the New Zealand grid.

The first thing people ask me when I tell them what we've done is, "How long before it has paid for itself?" My honest answer is, "I've no idea."

My thinking is not to try and prove what is going to happen in the future or make it all about money. The technology has been around long enough, and the price of the panels has been coming down long enough for me to get started and put a stake in the ground. We are doing our bit. With one proviso, we are going to wait another couple of years to see if the price of batteries is going to come down before we put them in.

So we have to use the electricity as we generate it, or we have to sell it to the grid. This has changed the way we use electricity in our household of three people. We have installed simple-to-use timers on both our hot water cylinders. One of them comes on at 9:30 am while the other bigger one comes on at 11:00 am and stays on until 4:00 pm. Our hot water cylinders act like batteries, storing the energy during the day and releasing it at night and the morning when we have our showers.

We time the dishwasher and clothes washing machines, both with their own water heating systems, to come on at mid-day when we are most likely to be generating electricity.

All in all, it is fun and the whole household is contributing to the effort. We have immediately bought our power bill down from around $230 per month to around $50 and April is not the top month for generating power; April is only the 8^th best month of the year for solar generation in Dunedin.

We have learned some interesting things about solar power generation -

• The real cost of electric power in New Zealand is not in the generation; we get 7 cents a kWh for supplying electricity to Trust Power which reflects the cost of alternative generation for the power companies. A significant cost of electric power for the New Zealand consumer is the cost of transporting the electricity from whence it was generated to the end consumer. The rumour is that 30% of the electricity is lost in generating power in the South Island and transporting it to Auckland. If true, what a waste. If it was generated where it was used, on Auckland roofs, that would be sensible.
• The economics of selling power to the grid at 7 cents per kWh but paying 25 cents per kWh for using power from the grid means that it is not economic to sell power, but it is hugely economic to not use the expensive stuff if we can help it. It is all about using the power we generate ourselves or storing it in hot water cylinders or batteries.
• Dunedin is as good as anywhere for generating solar electricity. Panels have become very sensitive to low light and this is important over the winter.
• The panels work pretty well on a cloudy day, especially if there is a ray of sunshine anywhere in the vicinity. The light pierces the cloud and bounces off the water in the harbour and back off the cloud layer and back off the water again. We possibly get to use the same rays of sunshine over and over!
• The solar panels generate electricity in direct current DC, and we have an inverter that takes the DC and converts it to alternating current or AC for the house and grid. Our array is capable of generating 6.6 kW of DC which is easily enough current to kill a person should they grab the wrong thing.

One way of looking at the capital spend in putting the solar panels on the roof (around $18,000 for our system) is to see it as forced savings. When I am retired my expenses will be lower at a time when my income has reduced. I delayed the consumption of that original capital years ago and I am reaping the financial rewards at a time when I will appreciate it. I use the same argument for my wine cellar too. Any pre-paying of expenses prior to retirement has to be a good thing?

We are having a great time as a family learning to live with solar power generation. Obviously we will be better off with batteries when we get them, and we are looking to up-grade our hybrid car to a plug-in hybrid so we can charge our vehicle off the roof too.

And climate change may even help.