top of page
  • Writer's pictureMike Casey

Our Renewable Energy System - Lets Deep Dive

At some point this week, we expect to have a large article written about us in the Otago Daily Times. I thought I would be proactive and provide much more of a deep dive into our system, energy and cost savings, so that other farmers and growers can determine whether some (or all) of our electrification journey can be applied to their businesses.

To provide some context, here is a sample gallery of all the equipment that we use on our orchard. From the 45kW solar array to the 120kWh battery array, the inverters and all the electrical machinery and appliances that we use.

Top Left: Forest Lodge Orchard Shed Top Middle: Shed with electric equipment and solar panels on roof

Top Right: The CerboGX controller we use to control our import and export to the grid Middle Left: 6 Quattro Inverters, 2 per phase, so that we can power all our electric frost fighting from our 120kWh battery array. Battery Array of BYD 48v LVL 15.4 batteries inside workbench.

Middle Middle: One of our two 30kW frost fighting fans imported from South Africa

Middle Right: Our 18.5kW submersible pump (inside bore) with pump shed and fertigation tanks

Bottom Left: An example of our future Monarch Tractor imported from California

Bottom Middle: Our 40 year old electric forklift Bottom Right: Borrowing our mate's Tesla to tow our most recent harvest down to the pack house.

If you would like to see our electrification in action, the gate is always open. Our philosophy is simply to show others what we have done and answer questions as best we can. We are all trying to wade through the inevitable transition from fossil fuels to electric technology.

The Payback on Electrification

Note: We are attempting to be as transparent as possible. Where we can we are using actual data, and where this is not possible we need to make assumptions. Some of these assumptions might be disputable but hopefully this will provide a base from which to build your own electrification case.

Here is the theoretical breakdown of our expenditure across key business functions with different sources of energy. Remember every farm is different, and so is every farmer so you might want to use different hours or different consumption rates to draw your own conclusions.

Fossil fuel (diesel/petrol)

Frost Fighting - 100 hours a season

Irrigation - 350 hours a season

Vehicle - 50kms a day

Tractor and Orchard Vehicles - 350 hours of use

Line Charges - single phase connection vs 130 kVA connection

Fossil fuel (diesel/petrol)






Electric (grid)






Grid + Batteries + Solar






Assumptions made

  • Diesel $2.70 p/L

  • Power 30c p/kWh

  • Power cost with solar and batteries 0.05c p/kWh average

  • 90hp tractor (10 litres per hour)

  • Two 30kW AGI electric frost fighting fans compared to two 2 blade fans consuming 40L of diesel per hour.

What is clearly evident is that the major savings in energy costs come from transitioning off fossil fuels directly onto electric technology. The savings from a solar and battery array are smaller but still significant. One thing is certain, solar and battery payback is cannibalised if you continue to burn fossil fuels.

Electrical equipment usually comes at a higher cost. In our case, we had to spend just over $100k NZD to upgrade our connection to the grid, our switchboard and harmonics to make this possible. Below is a table showing the additional capital cost associated with each business function.

Capital cost

Frost fighting

















Incremental cost of capital






And from these figures, we can work out the number of years of savings required for each business function (assuming diesel stays at $2.70 per litre and power stays at 30c per kWh).

​Payback Period

Frost Fighting




Incremental Capital

Under 2 years

Under 5 years

Under 2 years

​Under 12 years

​Total Capital

​Under 9 years

Under 11 years

​7 years

​21 years

The key reason "Equipment" is so expensive and has such a long payback period is that the electric tractor is one of the first in the world and must be imported from California. This, like the pay back on EVs, is expected to drop in the years ahead as prices fall.

Payback on Solar and Batteries.

We spent $216k to install our solar and battery array. This is a considerable amount of capital, and the requirements will vary dramatically from farm to farm.

We have built our system in stages over the past 24 months and therefore, unfortunately we cannot provide a full breakdown of our annual production and consumption. But we can do it over the last 6 month period.

If we were solely connected to the grid on our 130kva connection, we would have had a total energy bill of $9295 (based on 30c a kWh) in the last 6 months. We would have also had a $6000 line charge. Total costs being ~ $15000

  • Our actual consumption charges were only $1137 over the last 6 months based on our power bills.

  • We had export revenue of $1508 from power we added to the grid

  • Total line charges of $1761

So over the last 6 months, we saved ~$13,500 in energy costs from our system. In winter, we will produce less power, but we will also use less power without the need to irrigate or do extensive orchard work, so it's probably reasonable to assume a total annual saving of ~$25,000.

A total payback period of 8-9 years.

Not bad considering we expect our batteries to last 10 years and our solar panels to last 25 years.

Aurora has been incredibly helpful in working with us to help us reduce our burden on the grid, and therefore drastically reduce our line charges by only taking power during off peak times, and actively exporting power we have stored during peak times.

236 views0 comments


bottom of page