Free new tool launched by Auckland University that gives an economic estimate of the solar panel potential for most Auckland homes

Content supplied by Auckland University

The free online calculator factors in the unique “solar rooftop potential” of half a million Auckland buildings down to one square metre. This potential depends on such things as the roof’s slope and aspect, and shade from surrounding buildings and trees.

A new tool is available to help Auckland households and businesses work out whether it makes financial sense to install solar panels on their roofs.

“Solar generation is rapidly rising in New Zealand, with homes leading the trend. We wanted to offer an educational tool that is impartial and realistic to help people work out if solar is economic for their households or workplaces,” says Dr Kiti Suomalainen, a research fellow at the University of Auckland Business School’s Energy Centre.

New Zealand’s total installed solar capacity rose fivefold over the three years to 2017, and Auckland Council has a goal of 970 MW installed capacity of solar photovoltaics by 2040.

Dr Suomalainen devised the geographical 3D computer modelling behind the calculator. She used LiDAR data from Auckland Council, which is collected by planes emitting light pulses and timing how long it took for the reflected pulse to return to the plane, to construct a digital 3D model of the city with all its buildings and trees and other objects. With this, the solar radiation on individual rooftops could be calculated.

The calculator allows users to zoom in on their rooftop for a colour-coded view of its solar energy potential, which highlights the best spots to place panels.

You can also enter the size and quality solar panel you prefer, how much solar power you would use and how much you would sell back to the grid, and several other values. The calculator gives the total value (savings and revenues minus costs) of the installation over its lifetime. If it is positive, it’s a good investment.

If you want to investigate further, Dr Suomalainen suggests visiting (Sustainable Electricity Association New Zealand) for a directory of accredited solar panel suppliers.

“Self-consumption rate – the percentage of solar power that you use yourself, rather than sell back to the grid – is the main thing that will affect your economics,” she says.

“If you’re at home all day you will probably use more power than someone who is at work or school most of the day. For every kilowatt-hour of solar power you use, you save about 27 cents. The buy-back rate at the moment is around 8 cents – so the more you use, the greater the overall value of your solar generation.”

The calculator is now at a stage where users can test it and report any issues (e.g. mismatch of solar potential and underlying building on the map due to outdated building data). Dr Suomalainen welcomes feedback in order to make the tool as user-friendly and accurate as possible.

Try out the calculator here.

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There are many reasons why private home ownership is superior to our populations being subject to rapaceous speculators. This is a very important one. I expect that privately owned homes will install solar panels at an enormously faster rate than property speculators.

What a wonderful calculator, well done Dr Suomalainen and Auckland University. Just what I needed

Before I comment on this particular app I would like to make the point there are many better designed systems that do far more and are more accurate to provide actual analytical cost benefit analysis. On to this each region may have different lines operators, pay back rates for power, and sunlight generation is increasingly dependent on location,which this app completely ignores. (Such a large proportion of homes that have existed for decades have failed to even be identified or multiple separate standalone buildings are counted as one non existent building that the data is more fraud and fails even to the level of just throwing up google maps on a site.)

This app is so buggy and poor it is almost funny, (if it wasn't so very very sad). They should employ someone who knows how to at least code a basic website to rejig the thing. A junior graduate or even a first year student could do better. It is such poor quality that any useful information is missed due to the garbage data thrown from the garbage code. Hopefully no one paid for this, or if they did I would advise they should get it fixed by anyone else.

Why run this through the business school when even the under graduate engineers could do a much better job, hk even the maths and computer science undergraduates could do better data modelling and UI design. The business school is really for the non technical types who could not be relied on for anything more complex than basic arithmetic functions in excel. It really shows with this app. The failure of the map UI to even use decades out of date data and to use a basic form is laughable. By all means treat this information as you would any other site which gives a basic result from a sqm value without any sensible criteria like property location, effective sunlight times, household electricity use and peak use hours, materials and installation cost etc. It is as useful as a tabloid trying to poke a stick into thinking about solar using the dead dog of this site to show it.

And ...Have a nice day...

Should indicate this is an After Tax return so significantly more attractive.

Very much looking forward to your app. If I can be so bold to ask, please include a smug superiority ranking (with regard to neighbours roofs).

Reading the documentation of the model, conceptually it is sound. However, there are errors in the actual calculator on the website (as of 16/10/2017) which require correction before it is useable. At the moment it substantially overstates the NPV benefit because where it states $/kW investment cost and $/kW maintenance, it is actually reading these figures as the absolute$ value of investment and maintenance costs. Hence the model currently computes a 3kW system costing $3000 per kW, as only costing $3000 (i.e., it fails to multiply the cost per kW by the number of kWs). You can verify if the correction has been made by setting the buy-back and electricity rates =0, the economic life to 1 year and it currently returns a value of -$3,241, whereas this number should be closer to -$9,000. Seems like poor quality checking before website launch.

Should housing NZ fit all new homes with solar panels. Here they are negotiating for mass building of prefab homes by an Irish company.

Should not come as a surprise, we have to outsource parking our cars and picking up our rubbish, for crying out loud. Not much we won't outsource, when all of this stuff could be returning wealth to ourselves.

No. Why should they waste money building more expensive forms of generation than what we currently have? Shouldn't they spend that money on building more houses and upgrading the quality of existing stock rather than mucking around with uneconomic generation?

Yes solar panels are worth it, and why not take advantage of free energy in a 'solar rich' country. They're not that expensive anymore and even Elon Musk has invested in developing this technology further.

I'm surprised it hasn't become a standard requirement in NZ since the UK has been installing roof solar panels in new builds for the last ten years and the weather there isn't quite as sunny.

Tesla's Power Wall Battery pack is a game changer, it is finally arriving here and not just limited to one supplier, very exciting, I would love to go off-grid in central Auckland, but I suppose you would have to time it well, before the Government puts on some sort of tax to prevent everyone benefiting as they want to protect the power companies, big business not your average man on the street.

Actually while the power wall is a more expensive option there are several available low cost options for power storage many of which you can set up yourself. The Tesla power wall and Tesla solar roofs are fashionable but closer and more local operators have already been selling at this level already. You did not have to wait, well not unless you were just in it for the status symbol. It is exactly the mentality of waiting a few years for a Model S, (or a Porsche that cannot be driven out of the garage), that is out of date by the time you get it instead of being an earlier adopter in supporting the local market selling throughout those few years with battery technology that gets better with each iteration and can outstrip the Tesla when you finally get it. Tesla are not even very good at production. So chances are any non Tesla system will have lower maintenance, less replacement cost, and is easier to repair. Even China is outstripping America for solar. Which is not all that hard, and they are better placed to supply to NZ. If all you wanted was the brand then none of the purpose of solar is the reason you are buying. If you actually wanted effective household or business renewable "green" energy then you missed the early adoption boat and might as well get stuck in on research. Much of NZ already joined the bandwagon decades ago. Solar just has not been as cost effective in a wet, hilly, snowy country at the bottom of the world that gets plenty of geothermal, hydro and wind options.

I get the wind option loud and clear.

Many would not get enough sunlight or power output that it is not cost feasible (especially further down south in say a normal winter season). The costs of equipment are outrageous and while an office facility would have higher power usage during the day contrary to a home (so the power storage cost is not as necessary), the actual use varies a lot between types of buildings so again it needs to be cost feasible to do so, (especially since solar has such a high maintenance cost and poor long term resilience). Also many NZ commercial buildings have systems utilizing the more reliable forms of sustainable and environment friendly energy like geothermal, hydro, passive heating and wind. Plus there are some really good thermal energy saving features built into the structural designs. So many buildings are already making use of better systems than solar (which is costly on outlay, maintenance and refit and only one way for green energy). Top that off with most NZ energy being from green sources which are better place for NZ environment anyway, (hydro, wind, geo etc) and it becomes mute. Any system needs to be cost efficient in the long term (including maintenance and refit costs), resilient and appropriate to the NZ environment. Since NZ is already using green energy the tagline of it being "good for the environment" is not a useful point since most NZ energy is good for the environment and many newer buildings are doing sustainable energy designs much better already.

No, they are not economic CJ099. Building wind or geothermal developments is a much cheaper way to generate electricity in our renewable rich country.

The UK primarily have gas, coal or nuclear to provide their energy, as do Australia. In those countries that don't have our good hydro or geothermal resources it makes sense to subsidize solar as a way to become more renewable.

We're already 85% renewable in our electricity generation and new builds in wind, hydro or geothermal are all cheaper than solar. So why on earth would we want to subsidize or enforce the builds of less economic renewables ie solar over and above what we already have?

Makes perfect sense for UK or Aussie and absolutely no sense for us.

I have a grid-tied solar installation that gives me a negative power bill over the year. This means I end up exporting three times more than I use outside of daylight hours. with my energy-efficient house, this means a 5kW system. So, for the cost of this, I have achieved electricity bill independence.

Given that the panels will last 40+ years with little to no maintenance, this means I will probably never pay for electricity in my lifetime. The panels used are guaranteed to lose 1% generation per year. This is less than the increase in the cost of electricity.

One of the best ways to get a high self consumption rate is to run the hot water cylinder directly off the solar panels. I’ve been doing it for more than 2 years now and it works great. Two to three times in winter the water doesn’t get quite hot enough so the HWC ends up running off the grid for about 5 hours per year.

Solarking in Auckland lets you buy the gear youself and DIY it. You can get a complete 2 kw mono system with inverter roof mounts and rails for under $4000. As you say the hot water cylinder is the best way to maximize self consumption, and the best way to achieve that is with a power diverter on your hot water cylinder which is also a fun DIY project.

If you're smart enough to install it and lucky enough to have a north facing roof, then it's worth it.

I have a hot water heat pump that is programmed to run during the middle of the day. This has a double pay-off in that it is most efficient when the external air temperature is higher and it can run on the solar power. Easily out-performs solar hot water and no plumbing to the roof required.

Nice! that's pretty well optimised. I'm convinced that a solar install is also pretty awesome if you have a north facing roof, and if you can remove all of the labour costs, and if you are good with electronics and programming.

I use about half the power the average house uses. So no way would solar be worth it for me.
Most people don't even think about how far away the water cylinder is from the kitchen and bathroom and to have those hot water pipes insulated. For example, in my house if the second person goes into the shower within about 20 mins of the previous one, the water is still hot. You can jump right in immediately. I have old school separate taps in the shower so you can have it dribbling onto you if you want to save power and water.
Also, I have a wood burner supplied by trees on my own property so my power bill does not change much at all from summer through to winter.

I am thinking that the best mixture would be a wood burning fire for heating, gas califonts for water heating and solar for running appliances etc

Installing solar panels on my home wont work too well because there is a row of tall trees on my northern neighbours property that keep my house in shade for much of the day from autumn to late spring. As far as I am aware there is no legislation that helps my situation.

You can't shade a neighbours property with a building , not sure about trees.

If trees on a neighbour's property substantially interfere with your sunlight or amenities, you can apply for a court order directing the neighbour to trim or remove the trees. This is provided for by section 333 of the Property Law Act 2007.

For landlords go go near solar it would have to give some tangible return, either increased rent or improved capital value. At the moment the financial benefit seems marginal at best, or accruing mostly to the tenant. As my godfather told me "don't do it! It's just another thing they can f^*k up"

One big problem for landlords is that, as far as I can tell and I'm not absolutely sure but, solar is not tax depreciable! That's a big deal.

On the plus side Kiwibank is offering a "sustainable energy loan" which gives you $2000 cash back if you borrow $8000 or more for a renewable energy project.

The Nats have sat on their hands on this issue as well. Self generation is a great thing, and best much simpler if you are grid connected as well. But the commercial design of the grid is set up on the idea of huge generato points feeding a mass of very small users.
The future could be that the rooftop generation is a significant portion of the load. Grid needs to be set up for that. And if I set up a hillside of panels at the farm I should be able to pay a minimal amount for the grid to transport it to my townhouse 200 kms away, and to the office elsewhere.
So. A large significant reform of électricity market' so that it serves us, helps the new systems to develop and is not just another toll on us as we send electicity around.

"Self generation is a great thing.."

Only for the individual. Not for the grid. But everyone expects the grid to be maintained as a backup...
Its the opposite of economies to scale.

Haven’t you heard, in New Zealand the benefit to the individual outweighs the detriment to the many.

I see the future as a grid of interconnected islands. Each suburb could be energy-independent by sharing generation, storage and use. The grid is then a backup to connect these islands in case of shortfalls.

With a background in Electronics I have kept an eye on this over the years, yes panels have come down considerably over the years but there are other factors that you cannot put into the calculator, for example you put this in and then decide to move, how long is the electronics in the system going to work before it goes bang and how many people are living in the house ? The more people the better, it pays for itself but with just one or two then forget it even with a simple setup I worked out that doesn't need the electronics that will go bang or simply fail within 5 years. Still would only run solar if I was on an island or in the middle of nowhere and you cannot connect to the grid. Yes I'm sure it has a "feel good" factor but your better to just minimise your usage in many cases with more energy efficient appliances and put LED lighting throughout the house in the places you use it the most.

It's quite possible that the percentage EV's (with respect to the total vehicle fleet) might double every year for the next 10 years. That's exponential growth, imagine what will that do to electricity supply & demand. Many of the inverters are guaranteed for 5 years or more, and the panels should last for 30 years.

This link is to an article about connentting electric cars to the "grid", so that we can have/use a "collectice storage battery".
It makes the argument for solar power/electric cars even more compelling..

I feel amazed to be witnessing the natural transition from fossil fuel cars to electric cars.

But your electric car relies on fossil fuel tyres, roads, chassis, industry ...
Seriously - get a horse.

And then theres the not so clean side of clean energy ...
"Those countries mass-produce “clean energy” solar panels but do not regulate how toxic waste is dumped into the environment. "

Its all marketing spin.

Biological propulsion is less efficient than an electric car for the same amount of work.

Admittedly, we don't all need to be able to travel at 100+km/h so we do too much work now. An electric bike would be a good compromise.

Yes either electric bikes or even mass use of electric golf carts in urban centres would be preferable & far cheaper

Using you car as the storage device in your home system makes some sense, you have to have a battery in the car but I would avoid batteries in the house. Electric sounds great, right up until the point you get the bill for replacing the batteries, they simply don't last. If you look after your petrol driven car you can make the engine last 25 years, the same cannot be said for batteries no matter what you do.

Yes and no, you are only looking at first costs, you need to consider some other aspects ie TCO or total cost of ownership and resilience.

So yes ICE, car will last about 25 years (my one is 21years) but the maintenance costs start to rise and fuel consumption starts to worsen and its risk of costly breakdown and hefty bills increases.

Pure EV, low maintenance, things like no oil, filter changes, no plugs etc to repalce, maintenance costs substantially less.

So lets say you get to 10 years old, in that period how much have you saved in petrol and maintenance? probably more than the cost of a new battery.

Also the way things are going 12+years for a battery still offering 80% seems probable, and by about 2024 the cost of an EV will be the same or less than ICE.

Plus a used car electric battery still has enough life left in it as a house battery. Cheapest EV is a leaf and that comes with a 24kWh battery. Once the range falls to half its new range you still have 12kWh of storage (vs a new powerwall with 14kWh). So the Leaf battery will happily run your lower house loads for several more years.

By far the cheapest " battery " in NZ is additional water behind an existing dam.

Likely to remain so for many years yet.

And excess solar generation from rooftops can be use to re-fill this battery during daylight hours to be used at other peak times. Round trip efficiency of 80% for modern pumped hydro.

If you want to know how much sun (insolation) your site will get per year, I would recommend NIWA'a Solar View (free to use but login needed). This takes into account location, direction and local topography.

Converting the output to actual energy generated is more complicated. The easiest shortcut is to take typical generation for the location from existing users (e.g. 1300kWh/year in Chch) then scaling this by the amount your insolation changes versus an ideal installation in the tool (due north at angle equal to latitude)

NIWAs system and search is pretty good to get a better idea about the kWh/m2 for a given angle and location across a year. It also includes a good way to identify if any proposed site would be useful which opens it up to non & new house roof setups. NZ has such a variation on roof design, even in a given street, that for many the effective roof space would different across the board, (even some roofs which are sloped away from all sun for some design reason). That doesn't even account for apartment owners or those with a body corp who get the extremely short end of the stick. So many would look at other locations or ways they can generate power as a supplemental system.

Makes no sense to me unless the power companies start paying you a decent rate or offset your usage to pump your excess power back into the grid during the day when I'm not home so I can then come home and use free power and my total power bill drops to zero. Its not hard for me to put 4 panels on the roof ( I have the perfect north facing section of roof at over 35 Degrees pitch) and use DC heating in the hot water cylinder but still the payback is too slow if it saves me only $40 to $50 a month. It requires up front cost, maintenance and it can fail. The grid requires no maintenance and if it fails its someone else's problem to fix.For me it would fall into the category of a "Cool Project" to do myself but it wouldn't be to save a whole lot of money.