All across New Zealand, you can still find traces of decades past in the form of old houses. It’s hard to determine how old the average house is, but a study in 2010 revealed that many dwellings are well over 50 years old (or 60 from today). Homes built between the 1970s and 2010s are expected to make up the majority of the housing stock until 2050 at the latest.
During these years, solar technology had yet to be introduced or hadn’t been widespread. As a result, Kiwi homes back then weren’t designed and built with installing solar power generation systems at a later time in mind. And even if it was, the cost of setting up and maintaining one for home use was beyond what homeowners could afford at the time.
Modern technology has enabled solar systems to be designed for various home designs, including older ones. But before that can happen, the house has to undergo some major design updates. It won’t come cheap, but so will the damage if these changes aren’t made.
Despite its appearance, a solar panel isn’t exactly lightweight. SNZ PAS 6014 states that a standard panel for residential use is 1.8 x 1.2 metres in size and less than 25 kg in weight. The tempered glass is the largest contributor to the overall weight, necessary to shield the photovoltaic (PV) cells from dust and the elements. (1)
Additionally, Building Performance states that a solar installation won’t need a building consent if the solar panel arrays weigh less than 30 kg/m2. The guidelines prefer that the weight be kept within 15 to 20 kg/m2. (2)
Installing a solar power system is essentially asking your roofing system to prop up another roof on top of the current one. It isn’t a problem for metal roofs, which are lightweight but long-lasting, but it’s a different story for heavy ones like clay and slate tiles.
An expert team of residential solar installers typically advises updating the roofing system before any solar installation can begin. Propping up solar panels and their mounts on weak roof beams and trusses is a recipe for a deadly roof collapse. While there haven’t been any notable accounts of such cases, a roof collapse is usually decades in the making.
The installer may also take this opportunity to recommend reorienting the roof for the solar system to maximise solar gain. Given the country’s geographic position, north-facing roofs are the best for the job. That said, you also can’t go wrong with east or west-facing ones.
A solar power system turns a home into a power station (albeit a minor one for its own use, not for the wider community’s). As such, its electrical system has to be able to handle the current flowing from the panels to the inverter, then to the various home appliances and gadgets. A weak link in the system is a fire waiting to happen.
Electrical systems in old homes have components that have either long been phased out or deemed unsuitable for modern usage. Below are some examples.
Solar systems require electrical systems robust enough to handle the flow of solar energy. The energy generated by solar panels flows into the house through a direct current (DC). However, as homes in New Zealand use an alternating current (AC), the system converts its DC power via a power inverter. Some electric appliances convert AC back to DC internally.
Before a solar installation can begin, consider getting an electrician to audit the electrical system. Besides knowing what components are due for replacement, they may ask if you plan to add more electric appliances and electronics. The audit is also crucial if you plan to send solar power back to the grid (via a buyback program).
Modern solar power systems are designed to allow old homes to benefit from savings in energy costs. That said, they require extra steps to ensure they don’t cause more harm to the house than good. It doesn't hurt to ask a solar provider to find out more on how to get started.
1. “Residential solar photovoltaic (PV) and battery storage guideline,” Source: https://www.standards.govt.nz/shop/snz-pas-60142025 (download PDF)
2. “Notes for solar panel arrays: 14.1 to 14.4,” Source: https://www.building.govt.nz/projects-and-consents/planning-a-successful-build/scope-and-design/check-if-you-need-consents/building-work-that-doesnt-need-a-building-consent/technical-requirements-for-exempt-building-work/14-other-structures/notes-for-ground-mounted-solar-panel-arrays-14-1-14-2
3. “Electricity (Safety) Regulations 2010,” Source: https://www.legislation.govt.nz/regulation/public/2010/0036/25.0/DLM2763648.html