Zero Energy House
We're still connected to the grid like any other home, but at certain times of the day generate more energy than we need and sell this via the grid to an electricity retailer.
At other times we generate less than we need and buy electricity from the same retailer. To achieve Zero Energy, over the course of a year these must balance out so that we generate as much as we use.
This then needs to be compared against system cost. The system we chose to install was a relatively expensive, roof-integrated solution. We chose this partly for aesthetic reasons, and partly because we wanted to demonstrate what can be achieved with the latest solar solution design.
A standard system with the same rated output (4.16kWp), however, would achieve the same performance and therefore deliver the same value.
Such systems are available today for around $12,500. Adding that to a 25-year mortgage along with the rest of the housebuild cost would result in additional mortgage payments of $962 a year.
With the first year value and cost being basically equal, this shows a PV system this size on a house with this energy profile can pay for itself from the first year of operation. Then, in subsequent years, as energy prices increase (and assuming feed-in tariffs remain) the annual cost of the system stays the same but the value it delivers (by avoiding increasingly expensive imported electricity) will increase - the system then starts to return a profit.