Absolutely. Rooftop solar is the cheapest delivered electricity available to New Zealand households and finding ways to use it during the day is what is likely to save the most money on your electricity bills because you can avoid higher grid prices. 

On average, a solar install will cost 13c per unit of electricity, including upfront costs and interest on a loan. The average for a unit from the grid is around 35c, so there's a big gap.

Using solar to heat your water is the best thing you can do as that accounts for around 30% of an average home’s electricity use, and more if there are lots of people in the house. 

Those with a resistive electric cylinder and solar can basically use it as a ‘thermal battery’ and time it to heat during the day (some set their cylinders to overheat) and, if needed, on cheap night rates. This ends up being similar to the lifetime costs of a hot water heat pump. 

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Solar can also run other appliances in the house during the day so, if you can, it pays to set timers for things like dishwashers, washing machines and, if your house isn't too draughty, heaters. Any excess can be exported to reduce your electricity bill further, so nothing is wasted (shop around for the best deal on exports as they vary).

If you have an EV and it is at home for a least a few hours a week during the day, you already have a battery, so it makes a lot of economic sense to direct the solar into your car. Electricity from home is the cheapest fuel, and solar is the cheapest electricity.

Batteries are not yet an economic slam dunk in New Zealand and are primarily for resilience, but they are fun to tinker with, prices continue to fall, and Electricity Authority changes to rules that offer fairer prices for exporting at peak will improve the numbers. 

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Good batteries are important when you’re moving big hunks of metal, but when they’re depleted and not fit for driving, they can still work well for stationery energy storage and this is a crucial part of the transition to renewables.

Redwood Materials, the massive battery recycling company started by ex-Tesla Chief Technology Officer JB Straubel, recently claimed a record after it put 792 individual EV battery packs together and produced 63 megawatt hours for a small data centre that was set up alongside. 

In New Zealand, 'second life batteries' have been used at fast charging stations to limit stress on the grid.

If they can’t be used to store energy, the materials in these batteries are highly recyclable. For EV lithium-ion batteries, it is already the case that recycling can achieve >90% extraction of lithium, cobalt, nickel, and manganese [11]. Best-in-class recovery rates are as high as >99.6% for cobalt and nickel, and >95% for lithium [12]. Unlike fossil fuels, which are burned and need to be replenished, these materials are more like strategic assets. 

This is why we said in our Closing the Loop explainer that we need to approach the energy transition with a circular mindset, not a linear one. We also need strong regulation and incentives to improve recycling rates of metals and minerals, including strengthening product stewardship rules. 

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While batteries are individually small, they add up. As an example, just 120,000 homes (or five percent of New Zealand households) with a medium-sized battery could potentially reduce the peak load as much as our largest hydro power station, Manapouri. While these batteries would not hold as much energy as Manapouri, they could output the same amount of power for an hour or two when the system really needs it. 

Every home with a battery basically removes themselves from peak, and it could potentially remove their neighbours from peak, too. 

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If you want to completely go off grid you will need a very large solar and battery system to cover all your energy needs and you can face particular challenges such as town planning regulations. There are a lot of benefits for most New Zealanders remaining connected to a grid system, so we are not advocating that homes go off grid, but having solar and a battery ensures you have more resilience, control and independence whilst grid connected.

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Yes. 95% of a lithium battery has the potential to be recycled. Our explainer Closing the Loop shows that the renewable energy transition is a big opportunity to create a more circular economy. By 2050, more than half of the demand for materials like cobalt, graphite, and lithium could be met by recycled secondary supply. Others expect this to occur even earlier.

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Yes. New Zealand has strict standards that apply to batteries including the location and installation. If these are followed, the risk of fires is extremely low. 

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Most lithium-ion batteries are warrantied for around ten years, but some now have warranties for 15 years. How long they last depends on the conditions, where it is stored and how it is used. 

Smart energy management systems that monitor and control the charging and discharging of your solar battery can enhance efficiency and prolong battery life. 

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A 5 kWh battery is between $6,000 to $7,500, while a 15kWh battery is between $14,000 to $18,000. 

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It depends what your motivations are. It’s a firm ‘yes’ if you are keen to reduce your household emissions, improve your energy resilience and create an all electric home. If you are primarily concerned by the return on investment, unlike solar (which is an economic slam dunk for most homes today), batteries aren’t a clear call just yet, but those economics are improving every day and battery prices continue to drop by more than expected. 

It may well make financial sense if you are on a time of use rate for your electricity (where the cost varies throughout the day) or can join a plan where you can export energy at peak times and be rewarded for it, like those offered by Octopus Energy and Flick.

Rewiring Aotearoa is advocating strongly for batteries to become more "bankable" by levelling the playing field and paying customers that export energy at peak times, something we call Symmetrical Export Tariffs. This would show the true value of a battery and help to speed up the payback period and adoption.

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