Written by John Williams
Ongoing improvements in technology, price and performance make domestic solar electricity generation one of the few low-carbon energy technologies with the potential to grow to very large scale. And with Auckland enjoying in excess of 2,000 hours of sunlight a year, most of us are in a good position to be able to generate a fair chunk of our annual electricity needs by installing a bank of photovoltaic (PV) panels on our rooftops.
Interestingly, there isn’t much recent data out there about how we consume our energy at home, or the source of that energy. A 10-year analysis report on Household Energy End-use Project (HEEP) from 2006 suggests that space heating accounts for 34%, hot water 29%, with the remainder split between cooking, refrigeration, lighting and other appliances. Electricity accounts for 69% of the total energy (by type) we use in our homes.
Clearly, technology has advanced and building codes have changed since 2006, meaning many of our homes are now warmer and more efficient, but the fact still remains that the majority of the energy we need to power our homes – and increasingly our transport – comes from electricity.
As a starting point for what is a complex decision-making process, I asked Kristy Hoare, managing director of independent solar power quote service provider My Solar Quotes, to go through some of the basics that will help you to make a more informed decision on whether installing a PV system could work for you.
Before You Start
There’s no point in wasting energy, even if you’re generating it for ‘free’, so before you even think about installing a solar power system, you should ensure your home is well insulated (walls, roof, floor, windows, hot water), has an HRV system (if you’re living in an older home), that you have energy-efficient appliances, and have converted to LED lighting.
First up, you will need to assess whether your home is suitable for solar power by looking at the orientation, size and pitch of your roof, plus whether it is shaded by trees and/or buildings, etc.
A north-facing roof with a 25-degree slope is best for solar power in Auckland and the North Island (a 10-degree slope is the minimum). East or west facing will work, too. East-facing solar panels will generate more solar power in the morning and less in the afternoon, and vice versa with west-facing panels.
A bit of shading on the roof is OK. Solar installers can recommend different configurations to make sure the shading doesn't affect the system performance too much. Obviously, a completely shaded roof will not produce any solar power.
You may need to apply for resource consent to install solar panels, especially if you’re living in a special interest or heritage zone, or if there’s a chance the panels will affect height-to-boundary conditions. You will not need a building consent if you fix photovoltaic panels to your roof, or on a frame next to your building. However, if you plan to install photovoltaic panels as your roof cladding, you will need to apply for building consent.
The size of the system you choose will depend on your power consumption, roof space and budget. The average size New Zealand households are currently installing is a 3kW grid connect, solar power system, which typically costs around $9,000 fully installed.
Return on Investment
The return on investment largely depends on how much of the solar power you can consume directly. Using the 3kW system example, if you consume half of your solar power and export half (selling it at 8c/kWh) then your ROI is 8%. If you consume all of the solar power, then your return on investment would be 13%. This doesn't take into account the likelihood that power prices will continue to rise. If power prices keep rising, your return on investment will go up.
Some electricity companies will pay for your excess solar power, including Contact Energy, Genesis, Meridian, Trust Power, Ecotricity and P2 Power. The prices they will pay for your power vary, but average at around 8c per kWh. Trust Power has a new scheme called Solar Buddies, where you can arrange to sell excess solar power to a friend at any price you both agree on. Typically, people are selling to their buddies at a rate of 15-17c per kWh.
There are a lot of different battery options on the market, from small 1.25kW set ups to substantial 14kW systems. Battery systems are expensive – typically around $10,000 for the average household – but prices are expected to drop significantly over the next few years, roughly by 20% each year. Many people opt to install solar power right now, to start saving on their energy bill, then plan on adding a battery system in a couple of years when pricing becomes more favourable.
Solar panels are expected to last more than 25 years, as most come with a 25-year performance warranty. Lithium-ion battery storage units normally have 10-year warranties.
Solar panels will take two years of producing power to pay back the embodied energy of their manufacturing. They are highly recyclable as they mainly consist of glass and aluminium. There are also specialist recycling plants for lithium-ion batteries.
A growing number of people choosing to run electric vehicles (EVs) are also considering solar power, especially if they can charge vehicles during the day when the sun is up. Not only that, new technology from forward-thinking manufacturers, such as Nissan will soon allow homeowners to draw stored electricity from cars to power their homes if they choose.
The EECA (Energy Efficiency and Conservation Authority) has calculated that the fuel running cost of an EV is the equivalent of paying $0.30/L, or approximately 15% of the cost of running an equivalent-sized petrol vehicle. It also commissioned a lifecycle analysis of the environmental impact of EVs compared to internal combustion engine vehicles (petrol and diesel). The report confirmed EVs are better for the New Zealand environment than petrol or diesel-powered vehicles, across the lifecycle of the vehicle as well as in use.
Electric bikes are also becoming more popular with commuters and recreational cyclists looking for an alternative mode of transport. Once you’ve laid out the not insignificant cost of purchasing an eBike – anything from $2,500 to over $10,000 – you can expect to run it for very little in comparison to other modes of transport, with a full charge giving you more than enough juice to get into Auckland’s CBD and back, and costing a matter of a few cents.
Apart from charging it up, the main costs are battery replacement: $200 – $800 (every two-eight years depending on battery), servicing: $50 – $150 per year, plus replacement parts, like tyres and brake pads, but these costs are not substantial.
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