Sunny side to solar power
A new app suggests solar power’s biggest value may come when a property is resold, writes Catherine Harris.
Homeowner Carol Petrie needs no convincing about whether solar power pays for itself – she has cut her power bill in half. ‘‘I own about a 90-squaremetre house, it’s just me there, but I do have a spa pool and my power bill before solar, I was getting a bit stressed out.
‘‘My power bill was around $250 to $280 a month, which for me on my own was crazy. Now my power bill is averaging about $130 a month.’’
Petrie paid about $7000 for the installation.
‘‘A lot of people go, oh it takes X number of years to get your money back but for me, I had that mindset that I’d saved up the money and everything going forward was a saving.’’
She works away from home but the panels provide her daytime energy needs such as pumping water from a tank, weekend washes and the spa pool.
A diverter keeps her water hot. ‘‘I don’t have the battery, that’s in my plans in the future so I can store the power and use it at night.’’
With winter coming and lockdown having focused minds more on home, solar power is a talking point again.
Technology is getting cheaper but the biggest question around solar power remains how long the panels will take to pay themselves off.
At the moment, panels are a small part of the energy picture. The most recent data from the Ministry of Business, Innovation and Employment shows solar power rooftop capacity jumped 29 per cent in 2018. But, even so, there are only 21,037 residential ‘‘connections’’ with solar power, creating 75MW or just 0.3 per cent of all generation.
And while 40 per cent of New Zealand’s power is renewable, the biggest contributors are not solar, but geothermal, hydro power and wind.
It’s not the stellar future solar hoped for. In 2009, a report commissioned for the then Ministry of Economic Development on solar energy pictured solar energy would be costeffective by 2020, and a good alternative to diesel.
It believed that by now, solar would need ‘‘robust regulation’’, particularly as electric vehicles got under way. A decade later, electric vehicles are here but solar energy is still a marginal energy source for most households, although it is creeping into commercial property.
Fortunately, there are a variety of apps to help consumers decide whether solar panels are cost-effective.
The newest is property website Homes.co.nz’s solar estimate feature. Particularly useful for potential home buyers wondering about the sunniest part of a section, the feature shows a roof’s solar savings potential using a thermal image of the house.
The calculator also puts a dollar figure on the energy savings that one could make based on its sunshine hours.
So far the feature has been rolled out to cover almost half a million Wellington and Auckland homes. The median saving for a house in Auckland is $1140 and $1050 a year in Wellington.
‘‘We made some conservative assumptions to not overpromise in this space, but I guess what it does show is even in Wellington, where people moan about the weather, it’s actually a very valid place to install solar systems,’’ Homes.co.nz’s chief data officer Tom Lintern says.
However, the real saving might come when the house is sold. Based on a sample set of houses using a 3KW Harrison solar power system, Homes.co.nz found that the properties made 4.4 per cent, or $35,000, more than other comparable properties nearby.
The estimate does not include the cost of installation, which can be $4900 to $10,000-plus for a Harrison system, but Lintern says a property’s resale value should be considered.
‘‘It might be six or seven years [to break even] but what we want to do is shift the conversation to yes, you are going to make power savings each year but also you’re going to add value to your house.’’
Matt Lythe, of Lynker Analytics, which did the geospatial analysis, says the heat maps take into account the size, angle and orientation of the roof, as well as shadows from nearby trees, buildings and hills.
‘‘The heat maps allow you to understand where on your roof might be best suited to solar panels and also how you compare to your neighbours.’’
Another more established gauge of solar savings is on the Energy Efficiency and Conservation Authority website – the solar calculator.
Making the most of the sunshine hours is the key to solar power success. Batteries that store that power have improved but are still comparatively expensive. So while solar panels may not provide all a household’s energy needs, it may offset them.
‘‘Whether or not solar is costeffective for an individual household depends on a range of factors, including the orientation of the house, hours of sunshine, whether the homeowners are in the home during the day, and shading on the house,’’ EECA chief executive Andrew Caseley says.
The changes to EECA’s calculator now reflect differences in regional electricity pricing, and take into account, ‘‘load shifting’’ – which accounts for where households can change the time of day they use appliances for greater effect.
While solar has many fans, it also has its critics. There have been complaints in the past about fly-by-night installers, customers locked into contracts to their disadvantage, and questions over what happens when people sell their homes.
One solar panel user was being paid at about 8c/KWh for the energy he fed back into the grid, but was buying it back at night at 22c/KWh, an equation that EECA says has caught many people out.
Consumer NZ research found that the most cost-effective place to have a solar kit was in Hawke’s Bay, where it estimated the $6845 cost of installation took only 13 years to repay.
However, Phil Harrison, general manager of Harrisons Energy Solutions, says Consumer NZ’s breakeven cost is no longer accurate.
‘‘The payback periods will vary depending on the location and how you’re using the power but the payback is sitting somewhere between eight and 12 years.’’
He says some homes do get little sun and, for them, solar is not going to save them money. But for most, ‘‘the numbers stack up nicely and there’s a lot of things to take into account with solar, that’s why solar calculators can be a bit misleading. You really need to get a proper onsite quote.’’
The great hope for solar is storage. Batteries have become more commonplace in the past two years, but at just under $10,000 to $15,000, they are still not cheap. However, not everyone who buys a battery has a financial imperative in mind, Harrison says.
‘‘A lot of people put it in for control reasons, that they can now utilise all the power they’re generating.’’
Where solar is giving ‘‘exceptional’’ returns is commercial property, Harrison says, ‘‘because you’re utilising all that power during the day’’.
Commercially, the country’s single largest solar array, was at Yealands Estate winery in Marlborough, producing 412kW.
But that may soon be eclipsed by the 6000sqm of panels on Foodstuff’s distribution centre near Auckland airport and Marsden Point’s plans for a huge solar farm.
Seanz, the Sustainable Energy Association of New Zealand, represents the solar power industry and also has a calculator, the ‘‘solar optimiser’’.
To combat the problem of using more energy at night or in winter, solar installers recommend various technologies that enable load shifting, so that more electricity is used during the middle of the day.
Seanz’s research between 2013 and 2016 showed that median households saved about $647 a year.
‘‘It might be six or seven years [to break even] but what we want to do is shift the conversation to yes, you are going to make power savings each year but also you’re going to add value to your house.’’ Tom Lintern, Homes.co.nz’s chief data officer