Wednesday, February 21, 2018

First electricity bill after installing solar PV

Just over five months ago we installed 3.3kW of solar electric panels on the house. I've just received the first bill for a three month period with panels.

Our usage compared to the same period in the year before was down 46% plus we got a feed in credit of $82.

Last quarter our bill was $318, this time it's $226. Note that the included supply charge is $76.

We spent $6,000 on the system so at this rate it will take 15 years to pay for itself if electricity stays at the same price and you don't count interest on that amount.

Our usage has changed over summer in that we've used air-conditioning more on hot sunny afternoons where it's now virtually free and that's an improvement in comfort. I expect that the quarter we're in now will have a more dramatic saving as it includes the hottest part of the year here.

This graph shows usage and generation on a typical sunny day:

This graph shows a series of days of generation and direct usage:

A battery would dramatically increase the amount we use directly but at current prices I can't see it paying for itself for decades by which time the battery's life would be over.

Despite the long payback time of our system, I'm happy to have it and feel that it will add to the sale price of the house when the time comes.

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