Solar Power FAQ

Solar Power FAQ:

We get asked literally hundreds of questions about solar panels and general alternative power solutions so I thought I should start writing them down in one place with some answers.

Most of these are just quick answers for specific customers so may not cover off on exactly what you might be after but better than no information at all!


Happy reading!

(Note: the most recent questions are at the top of the page -so you can check back from time to time for updates.)

Q: I am enquiring about a off-grid system for a 3 bedroom house situated in New Zealand to cater for a family of 2 adults and 4 children and a monthly power consumption of 650 units.

On estimated costs: generally to install a solar power off-grid system to provide 3 kwh/day would cost about $30,000 incl GST (the ruld of thumb is $10,000/kwh of daily use. We recently did a system in ChCh that was $55,000 for 6kwh/day. So as you get into the larger systems the relative cost drops a bit.

Based on 650 kwh/month you would need a system that could produce 21 units per day. This would need a proper engineering design to be done but estimated cost would be around $160-180k. However, if you were to stay connected to the grid and install a grid-tie system then you could produce 8000 units per year with a 6kw array that would only cost around $30k installed. You would still be paying lines charges and still be connected to the grid but the cost/benefit is much better (unless you are paying huge lines charges). If your lines charges are over $80/month and if you think that you can get your power consumption down then an off-grid system becomes an alternative that is well worth looking into. The biggest way of reducing your power consumption is by not using and electricity for heating. this can easily be achieved by using bottled gas or solid fuel burners (which can also heat your water during the winter.)


Q: Perhaps you can help me. In talking to various people regarding solar panels. some have suggested that mono crystalline panels are much more efficient in cloudy conditions. Others seem to think that there might be a slight difference but not significant with the advances in multicrystalline panels. Any comment?

A: Thanks for your email. There is not a huge amount of practical difference in Mono Vs Poly PV panels in our cooler climate. We use Mono because of the higher efficiency that means we can get the same output for about 14% less area and panel weight than the same Poly panel. The poly panels perform better in hotter climates (40deg and up) so when roof space is not a concern these are often used.


Q: Are we correct in assuming that the grid-tie import/export meter would replace only our existing uncontrolled power meter (ie controlled power wouldn't be covered by the solar system), or do you normally replace the controlled meter as well and then have no controlled power from the grid? (Note: "Controlled power" means hot water, or storage heating that is turned off by the power companies to reduce the load on their network during peak times - you pay less for the electricity on a controlled circuit.)

A: We went straight to Meridian for this, here is their response: "...the anytime meter is swapped over for the import export meter and the controlled meter just stays in place with the same rates."
This means that you still benefit from the cheaper rates because your hot water is still run through the controlled meter while your solar only connects onto the Anytime meter so your electricity savings are made at the highest rate.


Q: We have a quote for a system that is cheaper than yours, what is the difference?

A: In a word: Quality. But that dosn't matter if you are not worried about the system lasting the long haul, however when it comes to solar power it is the last years of the system's life that are the most valuable. This is because the power prices are higher so the power generated by your panels is worth more to you, a lot more! Read more about quality here....

Read more about Returns over Time here...

Q: Also, talking to some of the solar vendors at the Fieldays they reckon Meridian's one-for-one power pricing will end at the end of the year, so they reckon to try and size the system so that it covers all of your day time use and that way you're not counting on selling power back to the grid. What are your thoughts?


A: I have heard all sorts of opinions (even some from their own staff) on what Meridian Energy might be doing in the future with their feed-in tariffs. I spoke with one of their staff members about a month ago who said that there was talk of them reducing their feed-in tariffs to exclude the lines charges, but then just at the fieldays I heard that Meridian have decided not to pull back on their feed-in rates for now, so who knows!?

The whole billing system is a little more complex than just a straight credit/payment on every kwh that is fed back into the grid from system. Each retailer has a slightly different way of wording it and I guess, implementing it. Some of them account for every unit sold and purchased and others tally it all up at the end of each month and others tie the month's credit over to the next month. I have normally advised customers to change to Meridian straight away but I am recently suggesting that they run for the first few months with their existing retailer to get real-life information on how they operate.

Which ever Retailer you go with, I don't think any of them will guarantee their feed-in rates for any great length of time, but I do think that the growing number of Distributed Generation customers will soon represent a large enough segment of the market to be an influence in the future feed-in rates for all the retailers. At the end of the day you are right to be thinking about generating less than the total amount of power that you use, we always recommend this because even Meridian won't pay retail for power from a net supplier, but dropping right back to just your daytime use level is not necessary because you still get a credit on that extra little bit of power you produce over your daytime use, although it may not be 1:1 it still makes a huge difference to the end result (reduced power bill). There are also ways that we can pull some of your power usage from night time to daytime through the use of some simple but smart automation. Time clocks can be put onto freezers and sometimes fridges and any other appliances can be operated during daylight hours through timeclocks or just manually. We do this with a lot of our off-grid customers to help save on battery useage.


Q: Do you sell the New Zealand Solar Panels using the Dye?

A: Wayne Campbell was the guy who was experimenting with the dye PV technology back in 2007. I have not heard of any advancements to market on this as yet but it is very interesting (and good to see this tech still coming out of NZ!) A lot of the latest tech that does make it to market is still very expensive ($ per watt output) and generally if there is no pressing need to use it most people will go for the Return on Investment over the "new tech" products.


Q: What does solar cost for a commercial building?

A: As far as cost goes - it is an open ended question and is only limited by your budget and roof area. The average returns on our systems (when customers use our importing partnership) are between 10-12%P/A for the first decade - that's about an 8 - 10 year payback. Then because of power price increases the return climbs quite sharply from there. The larger systems return the best because they take relatively shorter amount of effort to install and you get slightly better pricing for purchasing more panels. With a commercial system you can also claim depreciation on the equipment (as of 1012 this is at about 16% P/A but best to check this with your accountant)


Q: I want to take the fridge/freezer off main grid.

A: To take your fridge/freezer off the grid I would need the energy data on this (there should be an eco-star type rating on it that tells you how many Kwh it uses in a year) - from this we can advise how many panels you need. The best way though is not to install panels, chargers, batteries and an inverter (unless you have no grid connection to start with) but just panels and a gri-tie inverter - this means that when your fridge is not running but the panels are still in full sunlight that the excess power can be pushed back into the grid or used in other areas of your home.