27 February 2015

Why we've gone solar - photovoltaic power in NZ

They aren't pretty from the back - although I quite like them from the front - but there is a great beauty to photovoltaic panels.  We had twelve installed on our Hamilton roof just before Christmas, and they were switched on in early January (the delay was due to a wait for an electrical inspection).

The cost 

Just before we signed up for the panels, the main electricity companies dropped the price they pay to homeowners feeding power back into the grid. The drop was huge. We already knew, then, that this might not be a money earner for us.

The system cost $12,000 for a 3 kW system. Others will pay less for the same; we had the most difficult type of roof (concrete tile on one part, and tilt mounts on another) which hiked the installation fees, and we chose a more expensive microinverter system that cost an extra $2,000. Blame my house vanity for that. I didn't want the huge box that the cheaper string inverter system required in the house. (It can go outside the house if you have space near the switchboard.)

Our motivation

Despite the price, we decided to put our money where our mouths are, and chose not to think too hard about how quickly the cost would be refunded to us in the form of cheaper electricity bills (the payback period). If we think clean local electricity generation is a great idea, then we need to support the industry. If everyone stopped having systems installed because it didn't pay financially, the companies would go out of business. The great thing about solar panels is that they are on your roof where everyone can see them - you are advertising your principles. (Fortunately ours face the road.)

Plus, my husband loves them. He feels the same way about our panels as he does about his stack of firewood in the shed, and lying in front of a roaring fire on a cold winter night.

How we manage our electricity use

We had a short honeymoon period of having an old electricity metre that was wound backwards when we were generating more electricity than we used. It was brilliant. We even watched it continue to wind backwards when we switched on our heat pump as an air conditioner in the middle of a 28 degree day, then swing to spinning forwards when we boiled the jug. We got a rough idea of how much each appliance drew from the grid, and played around with things so there was as much backward winding as possible.

Now our import/expert metre is set up, we will be paid 7 cents per kW hour of electricity we feed back into the grid in summer, and 10 cents per kW hour in winter. We pay about 35 cents for each kW hour we buy in from the grid. So it makes sense to use as much of our required electricity as possible during the sunny middle of the day. We started generating about 7 am during the height of summer - although at that hour the amount was trifling - and it kept up for at least 12 hours on a sunny day. Now autumn is coming, the production hours are shorter.

So the dishwasher and washing machine should be switched on when the sun has climbed high, and if we get organised enough some cooking is also done then. It also pays not to use too many appliances at once - it's best to let the washing machine finish before doing the vacuuming, and finish the vacuuming before switching on the dishwasher. That way we know all our electricity is free; we won't use more than we are generating and have to commit that evil act of buying in pricey electricity from the grid.

Of course, that degree of management isn't always possible. We just do what we can comfortably fit into our routine.

Our clever move

Well, maybe it's not supremely clever, but instead of having all of our panels facing due north to maximise electricity production, we had three installed on a west-facing section of our roof. We generate less overall electricity this way, but we generate more in the late afternoon/early evening than we would with all north-facing panels. This, of course, is when we are more likely to be cooking the evening meal, so the generated electricity will be used, rather than sold earlier in the day for 7 cents and bought back in the evening for 35 cents.

Storing electricity

Ah, everyone wants to store what they generate at lunchtime so they can use it later. We can't do that yet - the batteries cost way too much - but we hope to be able to add that into our system one day.

The electricity bill

A snapshot from our first post-solar electricity bill.
Sorry the pic is so tiny: click on it for a bigger view.

Heh heh heh. We got a thrill when we received our first post-solar electricity bill. Here's a snapshot of it. Can you see the orange bar for this February, representing how much grid electricity we used? That's the almost invisible bar to the far right of the graph. It is minuscule. We generated more than we used, and got a credit to our account.

This did include a couple of weeks of the windback honeymoon mentioned above, when we were essentially getting a dollar's discount for every dollar's worth we generated. Plus it was an outstandingly sunny summer. I don't know if this lovely negative amount will happen again.

It definitely helps at this point to forget we paid $12,000 to be able to get this credit! But this is the first month of many more...

Our solar supplier

In case you're wondering, we bought our system from www.whatpowercrisis.co.nz. They were great.

Update for the following month's bill

In the following (also sunny) month, we used $60 worth of electricity. Before we got the panels, it used to be about $150 worth, so we're obviously doing a good job of using the electricity we generate while the sun's shining. Happily, we also exported about $30 worth, so our bill this month was $30 odd. Nice.

1 comment :

  1. Everyone is willing to have a solar panel of own. It may takes a big amount for the initial installation but it will save you a lot on your electricity requirement. It can also ultimately help in managing the electricity use. Switching to solar will also help in reducing the environmental pollution. You can also store electricity and save a lot on the electric bill.


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