Source: Radio New Zealand
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Falling solar panel prices and the rising cost of power have helped make the decision to put solar on the roof easier for many households.
But once you’ve invested in a system, how can you make sure you get the returns you’re hoping for?
Experts say there are a few things to think about.
First, how much does it cost?
The Energy Efficiency and Conservation Authority (EECA) says under the right conditions, a system would pay itself off for seven to nine years and could be expected to continue generating power for another 20 years.
It said a typical 5kW system would cost about $12,000 installed. Adding batteries would add to the price.
At a conservative estimate, a household with solar would save about $1000 a year on electricity bills. Power from solar could work out about 75 percent cheaper than grid electricity over the life of the system, EECA said.
EECA lead technical adviser James Le Page, the return would vary around the country, partly due to the number of sunshine hours areas had and also the network pricing.
“I’m in Wellington, and the power prices here are quite low … we’re quite near the main trunk line, whereas up in Northland it’s quite expensive. So that does factor into it, but certainly sunshine hours makes a big difference.
“So Nelson, Marlborough, Taranaki and the Hawke’s Bay, those sort of areas, you will be seeing probably better annual returns than say Wellington or Southland, which is down at the lower end there.”
What makes a household a good fit for solar?
EECA said solar would work best when houses had a roof with enough area oriented between Northwest and Northeast with a tilt of 30 degrees or more, where there was good sunlight and minimal shade, the household used a reasonable amount of electricity and when it could shift demand to daylight hours.
North-facing panels produce the highest output, but northwest-facing panels can still have 90 percent of the potential output.
Households with larger electricity bills generally stand to gain the most financially.
Le Page said people would only get the returns they were expecting if they optimised their usage.
“If you just pay for panels and have them installed on your roof and go about your life as before, you’re probably not going to see the returns you’re expecting.
“So it is really important to have that in mind when you’re considering solar, to go, ‘Hey, when this gets on the roof, we’re probably going to just change one or two things around here to really get the most out of it’.”
He said the most important thing was changing the time a household used power.
“For some households, it’s easier said than done. In the modern lifestyle, we’re out all day, come home at night, and at this time of year, the sun’s gone.
“So when the sun is hitting your roof and the panels, you’re going to be generating electricity, and that’s when you want to use it so you can get the best bang for your buck from your system.”
He said people might be able to schedule appliances to come on during the day, which could help.
“You might have an EV plugged in if you’re lucky enough to have an EV and can have that charging during the day as well to take advantage of it.”
Check your power plan
Le Page said people should also check the sort of plan they were on.
“You might find that if you stick with the same retailer forever, which some of us do, your electricity import rates might be too high, and also your solar buyback or export rates might be too low.
“You really want to be investigating with power comparison websites to make sure you’re on the best deal, and then you want to change the economics of how long your payback is going to be on the system and the sort of savings you should expect from it as well.”
He said sometimes having a flat pricing structure, rather than a time-of-use plan, would be a better option for people with solar.
“The reason I say that is because on a time-of-use plan, you would expect that the prices you pay for electricity should be at its lowest during the off-peak times, and that’s kind of during the middle of the day, when you should be generating electricity yourself.
“Now, it depends on your usage… but generally speaking, if you are getting a cheap rate when you’re generating your own electricity, and then when you come home from work, you’re paying premium prices at a time when you’re not generating electricity, you need to buy it back from the grid, then it ends up being more expensive. “
Maintenance matters
Le Page said solar did not require a lot of maintenance, but it could not be completely forgotten about.
“We live in a coastal environment, we live in a windy, dusty environment…bird poo, all sorts of things can build up on your panels over time, and that just impacts their ability to generate as much electricity as possible. So often, you might only need to clean them once a year, but it might be more frequently.
“Often with systems, you’ve got an app … So the day that it gets installed, you can work out how much power it should be able to generate at any given time, given the amount of sun on it. Now, this does go up and down over the year, because in the middle of winter, there’s not as much sun.
“But you should be able to work out from there, hey, something might be wrong here. It’s in full sun, and I’ve got a five-kilowatt system, and it’s putting out three kilowatts. What’s going on here? Is there a problem with one of the panels? Or are they really dirty? Do I need to get them cleaned? And so you can work out, you can troubleshoot from there.”
He said people might also need to keep an eye on shade.
“Solar works this year, but in five years’ time, that horticulture that you haven’t really looked at is now shading half your panels. So you need to keep an eye on that side of things as well, because it will have a huge, huge impact on the amount of generation you can get from the panels.”
Batteries and storage
Batteries allow households to store solar energy generated during the day for evening and early morning periods, which are peak use periods.
EECA said the cost of installing a battery would vary depending on the type and capacity, but was usually between $5000 and $15,000, including GST.
“While there are benefits from installing batteries, they extend payback times on investments for the majority of NZ households. As electricity pricing becomes more time-sensitive and peak pricing increases, batteries will become increasingly valuable.”
Le Page said using a hot water cylinder with a solar diverter or timer could be another way to store excess energy generated during the day. People could choose to heat up their water at times when they might not be using the power being generated.
“If you’ve got an electric hot water cylinder at home, you can think of that as kind of a budget battery in a sense because it stores energy in it, and if you can keep that up during the day, then you’ve got that.
“You don’t have to pay to do it overnight or later on, and you can actually buy diverters when you get a system installed that will make sure that you’re not feeding electricity back to the grid at a low price.”
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– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand