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Power bill reduction  

How much should my electricity bill go down with solar?

A typical 6.6kW solar install makes an average of 30kWh (units) per day

If you self-consume 10kWh of that 30kWh production it will save you 10 x 28.83 cents (current price of power from Synergy inc GST).

The other 20kWh would be exported back to Synergy who will pay you 7.135 cents per kWh.

Therefore (10 x 28.83) + (20 x 7.135) = $4.31 a day, or $263 per typical two monthly bill or $1,573 a year.

Most people will spend between $3,000 and $5,000 on their 6.6kW solar installation so they get their money back in 2 to 3 years.

You have a 1 in 1,000 chance (99.9%) of having a single panel failures over 25 years according to the NREL report on panel failure rates over time.

You might have to factor in spending another $2,000 in ten to fifteen years time on a second inverter to get you to 25 years.

Speculating how much power prices will rise over time, factoring in feed in tariffs, and battery storage price reductions, or battery subsidies is a foolish game, but even the most conservative estimate would suggest that you'll make $30,000 profit/bill savings from todays 6.6kW solar installation over 25 long as you stay in your home that long to enjoy the benefits.

Self Consumption of your solar production.
The more solar power you consume at the same time it is being made, the more you save.
On average panels on an East facing roof hit their peak production at 9am, North at 11am, and West at 12pm

North, West or East facing panels have pretty much entirely finished by 4pm.

We frequently get customers who say things like "My average use is 25 units a day, so if the solar makes 30kWh that will mean I have zero power bills."

What they forget is that their use is spread throughout the day and night whereas solar is only producing while the sun is shining brightly.

Unless you have a battery to store your surplus day time production for use at night, your surplus power flows immeadiately out to the grid and you get paid a quarter of it's value when you buy it back later on.

There's also the approx $1 a day charge that Synergy have snuck in recently that means even if you don't buy any power from Synergy at all, you still have to pay the daily charge.