Welcome to Stewart Island & Sails Ashore +64 3 219 1151 tait@sailsashore.co.nz

First Guests

We have the firsts guests of the season with us as I type this. So interesting to look at the impact they have on our energy usage.

This last month with just Iris and I here, we’ve dropped around 25% of total battery storage over night   … this is 6 kwh (units). Longer days mean the system will charge much later in the afternoon, and start much earlier in the morning, and of course early evening/breakfast power usage is thus carried by production, rather than storage. Our guests have added another 10 to 15% to overnight usage. Probably mainly because we run the boiler overnight, just in case they need central heating, or have super long showers…… generally they don’t, but we don’t take the risk.

Two Years Production/Consumption Data

We are not quite two years on solar, and the figures are quite interesting. To date our direct consumption …. panels to house … is 8884 kwh (units), and our battery supplied consumption is 6097 kwh, thus a total of 14981 kwh.

This total at local power authority charge of $0.85/unit is $12,734. Add to this the connection fee which we don’t pay as we are off grid of $2,380, gives a total electrical return to us of $15,114.11, or $755 per month. This may seem quite high, but we are all electric cooking ….. no LPG

Some of the consumption is running a heat pump, and also a back up 3 kw element in our domestic hot water cylinder. Thus saving diesel in our furnace. On cold nights we do run our furnace, as our hot water storage is insufficient to heat our home. But even so we have cut our diesel consumption to 30% of previous.

The projected returns on investment over all is well on track to be at least 13%.

Over Supply

We have no way to quantify just how much power we could produce if we could store our total production but  our batteries seem to reach 100% capacity by 0900 on a fine morning this time of year, and if cloudy by 1230. The excess unused capacity is significant. So much so that we are seriously considering a PHEV to replace our diesel powered SUV when it finally dies.

If Wishes were Facts

The big issue with a solar system such is ours is storage. Li batteries are expensive. But the technology is getting there, and from what I have read leading edge hydrogen storage could now store sufficient energy in a 3 cubic metre container to run our home for 2 months, without any external input whatsoever. All our domestic hot water and central heating  could then be met by heat pumps and so would make our home and transport completely free of non-renewable energy.