The 20th century energy system was one-way from generators to households. By focusing only on solar farms, we are, as a recent study said “using new technologies in an old-fashioned way, by centralising power generation in certain locations, in the hands of a few companies”. There are also land use issues with large solar farms, as they take up space that we could be using to grow food or trees (although recent advances in agrivoltaics do look promising). 

Households with solar on their roof will have the cheapest energy available and need to be seen as a critical part of our 21st Century energy system. If solar was added to all our approximately 2.2 million homes we could generate around 40% more electricity. Mid-size solar systems on our 50,000 farms could generate 60% more electricity. 

And we may not need as many new solar farms: academics from Auckland University of Technology pointed out that the 14 biggest rooftops in Auckland would be equivalent to New Zealand’s largest solar farm, while the rooftops of 167 schools and supermarkets would also provide the same amount of energy and be much closer to the point of consumption. 

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Compared to Australia, which has around 35% rooftop solar penetration, it is niche in New Zealand at around 3%, but it is growing as more people realise it is the cheapest form of energy available to New Zealand households and unlocks a lot of savings for electric homes. New Zealand's sunlight resource is similar to the state of Victoria and much better than Germany.

Even if we put a magical power plant in the middle of the country that generated free electricity, it would still be cheaper for customers to have rooftop solar panels because of the costs associated with all the poles and wires and the margins required for those businesses that provide it.

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We will need a lot more renewable energy in the future, but when they talk about big solar and wind farms, they only talk about electricity generation. Generation is less than half the total cost that customers pay. The price of distribution will still keep going up, no matter how much energy supply there is. Rooftop solar cuts out the middleman, by delivering energy from your roof straight into your home; no poles or wires needed, and therefore no distribution costs to pay.

Added to that, the price of grid electricity and fossil fuels is expected to keep going up, while solar basically locks in the price of electricity for decades. That’s why finance is such a key part of the puzzle in making rooftop solar affordable for all New Zealanders. The upfront costs are higher, but the savings are concrete; so we need to give everyone access to the finance to unlock the decades of cost savings and emission reductions.

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The recovery rates of materials in solar panels are already well over 90% and local company Phoeniix Metalman is recovering around 98% of the materials. But even with a massive global roll out of solar, the amount of solar waste the world might plausibly produce up to 2050 is equivalent to the amount of coal ash already produced globally each month. 

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Our explainers Electricity means Efficiency and Closing the Loop provide answers to all the waste questions. The short version is that electrifying everything will massively reduce the overall material and energy requirements of the global energy system. It is the epitome of doing more with less.

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New Zealand’s electricity grid is over 80% renewable and we should rightly be proud of that. But electricity is just part of our energy system. Around 70% of our total energy use comes from fossil fuels because we are so reliant on them for transport, heating and industry. We’re not so renewable when you look at it that way. 

Demand for electricity in New Zealand is expected to double or triple in the next few decades as we electrify our economy (and particularly our transport), and the lowest cost way to provide that to customers is through rooftop solar and batteries. That means customers can play an important role in the energy system, keep water in our hydro dams during winter and reduce the need for fossil fuel electricity generation. 

New Zealand's sunlight resource is similar to the state of Victoria. New Zealand currently has around 3% solar penetration, whereas Victoria is around 35%.

The more rooftop solar there is, the more it benefits the whole community as increased local power generation reduces the costs of power transmission. And in Australia, which has a much larger solar industry, it is also estimated that there are 39 jobs directly supported for every one megawatt of solar installed.

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Any excess solar you’re not using is automatically fed back to the grid (unless you have a battery). The Feed in Tariff or buy-back rate is what your energy retailer is prepared to pay you for the energy fed back. The biggest savings are made if you can use as much solar as you can when it’s produced, so it makes sense to set timers and use appliances and chargers during the daytime. Check different retailers to see their export rates as they vary considerably. Some homes with low-energy requirements can end up with negative power bills (i.e get paid by their electricity company) but most homes will just see a reduction in their bills.  

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. So ask your MP why cost-reflective two-way tariffs are not mandatory.

Monitor: Spend the first few weeks of having solar by using your app (your installer will help set this up) to monitor your energy habits and experiment with ways to match your consumption to the highest solar-producing hours (e.g. doing your weekly EV charge during the day on a Sunday). You might be surprised! 

Load shift: There is a lot of potential to maximise your savings with simple measures such as shifting more of your energy consumption to daylight hours. Use the delayed timer feature on appliances like dishwashers and washing machines, and set timers for hot water systems so they can be heated by cheap solar. If you have an EV, make sure you charge it via solar to enjoy huge energy bill savings.

Get off gas: Once you have solar, it makes more sense to remove gas appliances including your water heater, space heater and cooktop and install efficient, electric appliances. That is likely to be when they need replacing, but it may make sense to do it earlier, especially for health reasons. 

Invest in a battery: The next step is to consider investing in a household battery so the energy from the sun can be stored and also used at peak times. This is especially beneficial for those on time-of-use plans with their retailers as households can reduce peak usage from the grid and their costs. 

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• Inverter type: Microinverters are attached to the back of each panel, while string inverters are all connected. Microinverters are generally more expensive but are more effective and good for shady roofs or complex installations.
• Quality: Invest in high-quality solar panels and components from reputable manufacturers to ensure reliability and longevity. Better quality panels usually have higher efficiency and longer warranties too.
• Future energy use & system size: If you can, choose the biggest system you can afford and will fit on your roof. This is so you can accommodate any future electric needs (eg. electric vehicle). It costs less to install all at once and you can provide more electricity for winter use. To give you an idea, the average solar system on Australian homes is 9 kW, which can meet a household’s energy needs including two EVs.

A solar system requires a smart meter on your main connection, and if your switchboard is old it could also require replacement, but not necessarily. Your installer will tell you if you need upgrades as part of your quote.

In New Zealand, installed solar costs around $2,000/Kw, although it can be a bit more for smaller installs or less for larger installs. This cost also varies by region but installers regularly offer special deals. 

Rooftop solar is the cheapest form of electricity available to New Zealand households because the energy is generated where it is consumed and doesn't need to be transported.

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It used to be thought that solar panels were only good for north-facing roofs. With technological improvements and costs falling, these days it can be economical to put solar panels even on south-facing or shady roofs and many systems are designed with winter in mind. Your installer can advise you.

Solar installers we’ve talked to say there are very few roofs that are unsuitable for solar. 

If you are planning on moving house soon, solar may not make sense, but the average length of time people spend in a house in New Zealand is around seven years, so you can often pay off your solar investment in that time with your bill savings. And while it is difficult to prove, some studies have shown that homes with solar are more attractive to buyers and come at a premium. 

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Our household electrification guides offer a good rundown on how much you can save and how to make it happen. Households that have already installed solar are usually very happy to talk about it. If there is someone in your neighbourhood with panels, ask them about their experience or for recommendations and advice. 

You can also ask us (hello@rewiring.nz) or see if there are any electrification community groups in your area. If you decide to invest, always get a few quotes and keep an eye out for any special offers. 

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The recovery rates of materials in solar panels are already well over 90%. But even with a massive global roll out of solar, the amount of solar waste the world might plausibly produce up to 2050 is equivalent to the amount of coal ash already produced globally each month so it is tiny.

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Our explainers Electricity means Efficiency and Closing the Loop provide answers to many of the questions around materials and resource use. The short version is that electrifying everything will massively reduce our overall material and energy requirements. It is the epitome of doing more with less.

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