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

Solar Power Replacing Diesel Generated Electricity


Sails Ashore & Kowhai Lane both solar powered

Ulva Island Landing


As Close to Pristine as any place in New Zealand the public has access to

Sails Ashore Vegetable Garden

The Power of Compost

Our Stewart Island Environment

        …………   And where we are in it

Our aim is to give our guests the best possible experience with the least possible impact on the local community and environment.

We are committed to sustainable tourism and a sustainable lifestyle.

Stewart Island presents us with an ever-changing cycle as the seasons progress.

It always annoys us that we can only share the current season with our guests and so they miss out on the special things that happen over the rest of the year.

So we have decided to have an occasional diary of the things we notice around the village and on Ulva Island.

Stewart Island Environment

Just living in this world has an impact on the environment around us. We guess the trick is to keep our impact as small as possible. That’s not necessarily easy on Stewart Island as the Island is to such a large extent dependant on non renewable energy sources. The Island runs almost literally on diesel fuel, firstly for transport to and from the mainland, secondly the Islands electric power is diesel generated as there are no suitable rivers for hydro power and thirdly we use diesel for all our domestic hot water and central heating as it is the most cost efficient method available to us.

But for us that started to change in 2021. A guest was telling us about his conversion to PV  (Photo Voltaic). I suggested that Warkworth was somewhat closer to the sun in mid winter than was Stewart Island. But he told us that panel efficiency had improved in recent years and even grey days gave a significant out put. I build a small crude solar logger, and by July that year was convinced that it might just be a “go-er”

And so now both Sails Ashore and Kowhai Lane Lodges are Solar Powered.

Here is the story …………

Sails Ashore has two separate arrays… each one 7.04 kw, so just over 14 kw total

Each has is own dedicated inverter feeding our home and also a 24kw Lithium Ion storage battery. We are now completely “off grid”. In the event of several “dark” days we can top up our batteries with our generator set. Our historic consumption averages around 20 units per day over summer, and 15 units per day in winter. Sails Ashore is fully electric for cooking, having an induction hob and an electric oven
The project started when a guest told me of their solar experiences, and convinced me to at least have a look with an open mind.  So in the winter of 2021 I built a solar logger to record what we might expect in the way of solar energy, and from that I decided there might be 2 or at most 3 days a month over our winter period when we would “run dry”, and need a couple of hours gen set top up.. That was based on a 7kw array. This was installed and commissioned in November that year. We decided after a month of running this first array me might be just a little bit “light” and so added another 3kw. A couple of hours of bright sunshine being enough to bring the system up to full battery capacity. And even on a dull day we are producing around 2.5Kw which is enough to keep the system happy. This extra capacity also allows us to use excess generated capacity to heat our domestic hot water. This of course significantly reduces our diesel fuel consumption in our hot water furnace. Initially I had to monitor this and switch the electric hot water on manually when battery storage reaches 95%. And off again when the battery drops below this figure. I found a programable voltage sensitive relay online and it automates that function and works just fine. I monitored our hot water boilers run time, and showed a diesel saving of over 50%.  With the increasing cost of diesel we decided to install an air to water heat pump of 8kw output, and over the summer, with guests in the house we dropped our diesel consumption for domestic hot water and central heating to 25% of what we would have expected previously.  The extra load encouraged us to expand our panels on the second array to a total of 7kw. The difference is quite noticeable.

Generator Back Up

July 2023 has been quite wet and dark, and we’ve run the generator more than expected. But the total is still acceptable averaging over the previous 12 months just 8 minutes per day… this equates to less than a cup of diesel per day.   Initial issues with output of less than half of our gen sets rated output and at the same time panel inverters shutting down when running the generator have been sorted. Frequency “droop” when the generator was under load was the issue. We now have proper synchronisation and are getting a good 4.5 kw output, and the panels staying on line. This will have significant impact in reducing gen set run time. Today is the 2nd Feb 2024, and it’s been 180 days since we last ran our generator.

We massivly over produce electricity over summer and even on bright winter days and if we could store that I am confident we could be completely diesel free, possible even to being able to run a plug in hybrid car.

At present we calculate the return to us is around 18% on capital invested


Our Solar Blog Links in sequence :…………

Solar & Guests                                          19th Nov 2023
Gen Set Issues                                          19th Aug 2023
SIESA Renegs                                           12th Aug 2023
Solar Update                                              24th May 2023
Autumn, Energy, Sealions and things     22 April 2023
Red Admirals and Power                          12 September 2022
First Frost                                                  17 June 2022
Community Power on Stewart Island       1 May 2022
Solar Power & Spuds                                 5 Feb 2022
Sails Ashore is Solar Powered               12 November 2021
Energy on Stewart Island                         7 August 2021





Installing the second array on Sails Ashore Roof

For fire safety we built a small shed to house the batteries and electronics

The heart of the beast
Red units are solar inverters and the yellow the battery manager and inverter.
The white units are the 24kw Li battery system

Panels on Kowhai Lane roof

Management. What we see.
This is our 1st 7kw array production graph at midday, 27th March


Management. What we see.
This is our 2nd 7kw array production graph at midday, 27th March



Management. What we see.
Battery Storage 27th March. Showing a charge of 5.95 kw.


Economic Return as of 02-February-2024
Diesel Savings is the result of electricity replacing diesel for hot water 



Management. What we see.
We can access this overview via any internet connection


Kowhai Lane

Once we had commissioned the system our daughter Anne was so impressed with our first full months electricity bill she decided not to wait until spring but to have 5kw installed on Kowhai Lane Lodge as soon as possible. ( At that stage we were still partially grid ties). And it was installed by Tansley Electrical when they put our second array up. Kowhai Lane is quite different to Sails Ashore in that it is “Grid Tied” Feeding excess electricity into the local power system, and drawing from the system when demand exceeds P/V supply. This makes sense, as there are significant periods when the property is empty, both during the day when guests are out enjoying the Island, and of course when the house is unoccupied.
The timing of the project was quite fortunate, as Tansley’s manager told us when we ordered we had the last of a shipment, and the next would be 22% higher cost.

Electrical Power Consumption since November 2021

The heading link will show Sails Ashore power consumption since it was commissioned in November 2021. The “Total” figure is the Kilowatt Hours (KwH) consumed
Please note that this is what we used, rather than what we could have produced. On a bright day our batteries will be fully recharged in 2 hours. Overnight use varies between 25% of total storage in summer to around 40% in winter. Once our batteries are full we divert 2 kw into our water heating heat pump  and 3 kw into our hot water system, which, in summer means we burn no diesel in our furnace unless we have guests in house. Then, we might run the furnace for 3 or 4 hours in the evening. In Winter we may run our furnace in the evenings for domestic heat,

When we were on the local grid we averaged around 14 to 15 units per day. We are now averaging around 23 units per day.

Sails Ashore and the Stewart Island Environment

Sails Ashore was designed to make full use of passive solar energy. The sun room faces north and with full double glazed windows towards the sun and full wall, ceiling and underfloor insulation through out ensures we keep heating costs to a minimum. . Stewart Island is a bit marginal for solar water heating, but newer technology is very interesting and may now make it viable. Quite apart from the conservation aspect of fuel minimisation the rapidly increasing costs of liquid fuel certainly focuses our thinking on efficient use of energy.

We sort all domestic waste and recycle wherever possible. A large compost bin and worm farm deals with garden and food waste and also contributes to our organic garden and glass house fertility. In addition we collect lawn clippings from the local community lawn mower, this in total turns into around 6 cubic metres annually. We grow as much of our vegetable requirements as possible.

We are now changing to  LCD light bulbs , replacing even our older fluorescent bulbs, as although the energy savings are minimal, the vastly superior life expectancy makes this a “no brainer” . We have timers and dimmers on appropriate circuits.

All our domestic water is collected from our roof, stored in large tanks, UV treated and micro filtered before use, exactly as “Stewart Island Rain” bottled drinking water is prepared. And Stewart Island Rain won NZ’s boutique bottled drinking water competition so it’s pretty good water to drink.

Sails Ashore

Facing north, with sheltering trees to the south and west and full state of the art insulation minimises heating costs

Waste Management

Iris and her worm farm. Apart from onions and citrus which can kill the worms, all our kitchen scraps end up here.

Fresh Compost and worms

We make around 6 cu metres each year.

Planting out our glasshouse

Tomatoes and grapes would just be a dream without a glasshouse.

Rakiura Environment Trust

Like many places in New Zealand, Stewart Island has it’s share of introduced mammalian pests. In particular rats, opossums and feral cats are to be found around the village, as well as the wider Island environment. A local trust has taken on the task of trapping and poisoning these pests within the village and in particular the Ackers Point area.

The result has been quite impressive with so far this year almost a 1000 rats being trapped. Stewart Island Robins have been reintroduced to Ackers Point and the ultimate aim is to release Saddlebacks. Neither species can survive with rats.

We have noticed and with our guests enjoy increased bird life in our garden. The work of the trust can only improve this for the enjoyment of all.

As well as bird life we are noticing a significant increase in small plants such as orchids within the trapped area. Many of which are difficult to find further back in the forest. We service one line of some 30 odd traps based around Observation Rock and down as far as the Post Office.

Quite apart from the bird life rats are a problem for any householder and as well can do significant damage in a vegetable garden. This winter we have not noticed any rat sign for the first time ever around Sails Ashore or Kowhai Lane and “our” trap has caught only two.

The trust is funded entirely by donations and although there is a paid staff member, much of the work is done by volunteers. We have post cards by Gilbert van Reenen on sale and all profits from this go to the trust and in addition many guests ask to make a cash donation. Thus helping enable the work continue.

Both Kowhai Lane & Sails Ashore are honoured to each sponsor 5 hectares of Habitat Restoration

The trust has commissioned a study to investigate the possibility of eradicating rats, feral cats and opossums from all of Stewart Island.

It makes very interesting and thought provoking reading and with the success of Ulva Island showing the way is perhaps the future for Stewart Island.


Stewart Island Electricity is generated using diesel fuel

Sails Ashore is Solar Powered

 But we now produce 100 % of our electrical needs, and are completely "Off Grid", Excess electricity is used to heat our domestic hot water and central heating system and this has cut our non renewable heating fuel usage to around 20% of pre solar.. All cooking is electric, no more LPG.  See More .......

Kowhai Lane is also Solar powered,

Kowhai Lane is "Grid Tied" Excess production is used to heat water. Production beyond the house requirements is exported, thus cutting diesel use in the wider grid. At night Kowhai Lane Lodge receives power from the grid.

Like Sails Ashore, all cooking is electric,,,,, No LPG



Sails Ashore, Kowhai Lane & Sails Tours

11 View Street,
Stewart Island, 9846

+64 3 219 1151
Email: tait@sailsashore.co.nz
Web: www.sailsashore.co.nz