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Scott Willis

Hi Phil,
I do have some data that I should be pulling together in any case for BRCT, but in the meantime, rule of thumb we have is that a low user household should aim for approx. 2kW array, while a high user household should aim for a 4kW array.
There are many variables to consider:
– Is anyone home during the day? If so, it enables a higher percentage of solar electricity to be used when it is being generated, offsetting any bought off the grid.
– Will the homeowner also incorporate timers and other bits of kit to move load around?
– Is the homeowner willing to make changes to their lifestyle to make the most of the solar? (the answer to this is always yes actually – everyone does it when they see the benefits it has).
– What space do they have for solar? Roof space and aspect may be a limiting element, but some homes have space to ground mount or sheds, garages, etc.

FYI, in our community we range from about 38% to 58% (roughly) of solar electricity generated being used on-site at the household. I know in our own house we are over 50%, but that’s because we pay attention to appliances and my wife works from home.

One of the biggest motivators people have at present comes from the market: there is no point exporting more that 5kWh of solar electricity per day, so unless you are rich and green and just want to do good for the environment, you should aim to build a system that will match, roughly, your demand and try to keep within the 5kWh export threshold (Meridian). However I should point out that the market is a political construct and if there is a Green/Labour government after the election we are likely to see greater market certainty and ease for small scale generators.

So I guess what I’m saying is, the infrastructure is costly and a fixed asset, but the market is mutable – so don’t limit options. Strategically, this means from my perspective: build to match today’s consumption, prepare to clip on more when conditions improve. This involves consideration of how to add in extra ‘strings’, selection (and life-span) of inverter or panels with micro-inverters, etc. I think I’m making it sound more complicated than it really is…

What we all have to confront in NZ is an electricity market that doesn’t really want distributed solar and so what is happening is that solar installations and homes with solar are increasingly working organically to grow the percentage of solar electricity used within the home – either through staggering appliance draw, or through adding in storage as well (minor as yet outside of the Vector zone, but becoming much simpler).

When we get our information into a sensible format I’ll provide it here.