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Topic # 161741 18-Jan-2015 12:32
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A friend of mine told me he's keen to get solar power for his house, I thought I'd run it past people here to see if they had any thoughts or useful advice. I can get proper details if anyone's interested.

The house is in a Wellington suburb, on a peak, with a perfect north facing roof. The house has four adults and two kids, including two hot water cylinders and a spa pool, with people occasionally home during the weekdays and home most weekends. An electric car is a possibility in the future, the idea being to charge it on the weekends for a weeks commuting. They're not thinking about storage batteries right now, but might think about that in a few years, so they system will be designed to accept them later. Their power bill is fairly high, from memory they said around $300 - $400 in summer and $600 in winter - TBC. It's an older house, relined, double glazed downstairs where it's a self contained living area, but single glazed upstairs where the main living / sleeping area is.

The system will has some kind of a gizmo (I forgot what he called it) which channels the power into heating the hot water during the day, preventing them heating in the evening - though I guess there could be an override button somewhere. So while there's no power storage the water heating is storage of a sort.

The panels and install are costing around $12K for 20 panels (no idea of brand/spec) and $1500 for the power router thingy.

Does solar sound like a good option/solution to reduce their power bills?

Edit - it's a 4kw system from Harrisons and the device thingy is an "immersion hot water device" that sends power where you want it to go.




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  Reply # 1216905 18-Jan-2015 12:49
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Have a look at http://www.geekzone.co.nz/forums.asp?forumid=73&topicid=160637 and http://www.geekzone.co.nz/forums.asp?forumid=73&topicid=153861 The biggest factor in how much they will save, is how much power they can use directly. As this means you are effectively getting paid at retail rates for your solar. Also you need to check if they only have a single meter. Or if they have multiple meters / phases. As you will loose alot of savings if you are exporting power through 1 meter while you are importing power at the same time through a second meter. Alot of people with 3 phase power have been caught by this. As they only have single phase solar inverters.





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  Reply # 1216928 18-Jan-2015 13:53
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I would only get solar to cover what I can use for sure during the day at the moment. Sell back isn't a guaranteed thing to base your figures on.

1.5kw on my shed should do it. Maybe 2kw to allow for getting the pool back working again.




Richard rich.ms



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  Reply # 1216969 18-Jan-2015 15:07
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Yeah I've read those threads. Just curious about experience/thoughts for this situation.

I've updated the first post with slightly more information.




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  Reply # 1217024 18-Jan-2015 17:26
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Personally I'd swap the hot water tanks for either solar assisted jobiess, or ditch them entirely for gas on demand hot water before going for solar electric.

I'm on the Vector Sun Genie setup (4kW of panels and a 10kWh lithium battery) and that's working out quite well. Plus we have an on-demand gas hot water heater, and I'm thinking of getting an on the roof solar heater for the water as well once enough pennies are saved.

Past 30 days my house has used 597kWh, of that 369kWh was from the solar panels and battery and then another 225kWh was exported back to the grid, so I pulled 228kWh from the grid.

House of 2 adults and 3 kids, 4 of those people have hardly any regard for saving power and run aircon, fans, lights, water pump practically all the time! :-)







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  Reply # 1221714 25-Jan-2015 09:31
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We installed a 2kw system to cover our day time usuage and also have solar hot water.  We have generated 310 kwh for the month  and imported 60 kwh from the grid.  As for the solar hot water we have not imported anything for that and according to the controller on average water in the cylinder is at a temp of around 80 degrees C.  This setup works for us well and certainly covers all our daily power needs.  When we initially looked at having the system installed being the typical male I thought bigger was better, however our solar consultant from the company we used looked at our overall power usuage and suggested this size pv setup. We have 8 solar panels on the roof with a 2.5kw SMA Inverter.

We are also looking at the Immursun as well to suck up the remainder of what we export but need to do a bit more research about it before commiting.  Along with the solar hot water we have a wetback as well on the woodburner which covers our winter hot water usuage so not too sure if the investment would be worth it at this stage as we are fortunate and have plenty of firewood to cover our winter heating needs.

We run all our appliances during the day including the aircon and still manage to export but it is not a lot 

I know people talk about buy back rates reducing, but for us its about using what we generate rather than sending it back to the grid, and that is where the saving is made in your overall monthly power bill.  Im happy the solar consultant from the company we used talked me down in size it saved a few dollars and this size certainly works for us.

We are a family of 2 adults 1 child and 1 teenager, but when the weekend rolls around during the school year our house swells to 2 adults 1 child and 3 teenagers along with numerous friends of the kids the rock on in and the system copes.

Picture of whats on Our Roof 

Solar on our roof

Thanks 



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  Reply # 1221742 25-Jan-2015 10:31
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Thanks N, that's really interesting/useful.

btw here's the proper image you tried to link - something went wrong when you did it.





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  Reply # 1221771 25-Jan-2015 11:09
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Many thanks for sorting the photo out and all most welcome for the info 

Thanks 

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  Reply # 1221782 25-Jan-2015 11:34
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Forgot to mention their is a website where you can view solar output data www.pvoutput.org.  There are systems in Wellington that upload their generation data frequently during the day.  Do a search for Wellington Solar that is one system uploading data, along with a few others 

Hope that helps 

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  Reply # 1222903 27-Jan-2015 01:46
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Its more efficient to use photovoltaic (electric) solar panels to run a heat pump hot water cylinder than it is to capture heat directly from the sun.
The immersion device sounds like a standard element to me- which isnt as efficient.

Although sellback in the future isnt guaranteed, the excess power would be more than enough to fill the hot water needs, and sell back some rather than just use it all on a less efficient way to heat the water.

I have heard of installers designing the heat pump systems to take warm air from the attic, rather than putting them outside which makes them super more efficient as the attic can get upwards of 40 degrees, so it uses very little energy to transfer that into the water cylinder - taking you over half way to your 60 degree goal, rather than extract heat from 20 degree air outside at only a third of the goal.




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  Reply # 1222926 27-Jan-2015 07:32
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Some good ideas there Ray, but then you have to spend the extra $4K or $6K (can't find prices online) for the heat pump hot water heater - in addition to the $12K hot water. Of course my friend has two hot water cylinders and a spa pool, so he'd need two and the spa wouldn't have one. They have heat pumps, so in summer they might choose to run the heat pump to cool when there's excess power generation.

My ceiling cavity is getting up to 45 degrees at the moment, but in winter it's a lower temperature even on sunny days. Putting in ducting to get that much air out of there would be interesting, given the main unit needs to be outdoors and it blows a lot of air through. I know heat exchange ventilation systems can use that air, personally I'm just changing my ventilation system to prevent it using ceiling cavity air as my 100 year old house has really poor air quality up there.




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  Reply # 1222944 27-Jan-2015 07:54
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I have not had much experience with photovoltaic but we had solar hot water on the roof in our last place it saved lots on the power bill.  Our bill used to be between $100 in the summer and $150 in the winter.

Our new place has electric hot water and the bill is $200 - $250.  So it appeared that the solar hot water saved around $100 per month on the power bill.







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  Reply # 1222945 27-Jan-2015 07:59
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What city CyberHub - when I mentioned solar hot water someone said it wasn't warm enough in Wellington.




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  Reply # 1222948 27-Jan-2015 08:09
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A big problem with trying to run heat pumps using solar generated electricity is you cannot guarantee the power being delivered. So if the sun goes behind a cloud then the solar will drop suddenly and your heat pump will begin importing from the grid. Since you can't switch heat pumps on/off rapidly they are generally not the best choice for solar PV diversion.

That is why a HWC element is so good, you can have it flicking on/off as rapidly as you like with no ill effect. 



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  Reply # 1222950 27-Jan-2015 08:11
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That's probably why my friend is doing it, three cylinders and a spa is a lot of water to heat. Any excess can be running the fridge such, exporting a little to the grid if there's any power leftover.




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  Reply # 1222954 27-Jan-2015 08:19
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I think one key thing if that you should never rely on $ selling to the grid when looking at your business case. Electricity companies are acting out of kindness paying you significantly more for electricity than they're paying elsewhere most of the time.

You've also got to factor in the grid was never designed to have multiple ingress points, and eventually you will reach a point where a grid can no longer have more electricity fed into it locally because it will cause voltage instability, and more importantly once power is generated it HAS to be used somewhere, whether that be consumption, or loss due to distance.

I've seen a number of people comment lately that "they should just fix the grid to overcome these problems" which poses the question of why a lines company would want to invest money into completely redesigning our electricity grid. Surely in the real world it'd be home owners who contributed if they want to get money back? :)

Once battery capacity pricing drops solar will be a game changer.




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