Solar panel installation questions

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362 posts

Ultimate Geek
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#2046712 1-Jul-2018 10:59

That's changed the whole picture for me!

Not sure there are other cases it might be possible, but even if my whole roof covered with solar panel (7-8kW), they will hardly cover half of my May monthly usage (940 kWh) during winter months.

Then I will probably get hot water gassed and might be cooking as well before even consider solar, otherwise currently the plan is solar and using time-shift or better diverter to offset 30% plus of hot water bill into solar, then battery, but better to get gas into the equation, otherwise sloar plus battery not going to fly as what's the point of go solar but still paying back hefty fees during winter and not really off-grid event spend money get battery installed.

How much cost for bottled gas for heating, I was looking at pipe gas heating (not really off-grid I know), but fixed charges, and monthly fees, doesn't looks like really saving for me? Plus I need pay got get my house connected with gas even my street is connected.

MichaelNZ:

pstar008:

Nah, that's cheating, you can't go wrong with that guess, it's so obvious ...

Think about it, go with gas will make PV solution and eventually off-grid much cheaper.

But as you guessed again, I think I am going to stick with PV route, simple because I believe it is the future, but again, as you said: gas can be part of PV solutions, which never really stick to me until now. Thanks for that!

You must use an alternative energy source for heating if you ever plan to go offgrid.

PV does not produce enough power year round to replace electricity for high demand uses.

Gas is the easiest because it works year round, is a lot of energy for it's storage space and does not require a permit to install.

It's also on-demand - a definite benefit in the warmer months.

pstar008

362 posts

Ultimate Geek
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#2046721 1-Jul-2018 11:26

For anyone have bit of time to know how optimizer works for SolarEdge inverter, which seems like the market leader, and they do have a 25 years warranty, which does sounds good.

The SolarEdge power optimizer is a DC - DC power optimizer integrated into each module, replacing the junction box.

https://www.solaredge.com/sites/default/files/se_application_fixed_string_voltage.pdf

So the optimizer figure out the right output DC voltage, and to the inverter all output from optimizers will be in a string. There is no MPPT in their inverter and no micro-inverter involved.

Aredwood

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#2046754 1-Jul-2018 12:58

Electric heating via heatpumps will still be a lot cheaper than bottled gas. And probably still cheaper than piped gas. Still use gas for cooking. As it is very difficult to time Shift cooking. And if there is a power cut, you can still cook.

Hot water via electricity might still be cheaper than bottled gas, if you have night rate power available. Although gas hot water will most likely reduce your power consumption enough, that you will then qualify for the low user plans.

Don't assume that power prices will always rise. My current power price is less than 5c per unit higher than what it was 11 years ago. And some of that was due to the GST rate increase. Also there could be structural pricing changes to how power is billed. Imagine if say daily fees increased to around $5 per day. And per unit costs dropped to half their current price or even lower. Average households would still pay approx the same amount per year for power. But goodbye to savings from having solar panels.

MichaelNZ

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#2046755 1-Jul-2018 13:06

Decide what your long-term options are. Both @Aredwood and myself are correct, even though we contridict each other - because it comes down to what you want to achieve.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers | ZL2NET

Aredwood

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#2046787 1-Jul-2018 14:15

If you want to go off grid. It is far cheaper to offload as much of your power usage to other energy sources. And invest in energy efficiency. Than it is to build a bigger off grid power system.

While if you remain on grid. The low user rates mean that is only costs you 33c per day to stay connected. While the artificially high unit rates on the low user plans inflate your savings from solar. And also mean that you can make good savings by shifting major usage items to gas. (indirect subsidy for emitting more carbon dioxide).

A lot depends on what pricing plans are available for power and gas in your area. So you are therefore making a large gamble that those plans won't change. And an even larger gamble since you will be borrowing against your mortgage to fund the installation. While simply paying off the mortgage is equivalent to earning your mortgage interest rate on an investment. After tax, which is also completely risk free.

Still consider scenarios such as needing to replace your hot water cylinder. Or needing a new car. Is gas hot water a better option, maybe a much larger hot water cylinder heated by night rate power. Consider getting an electric car. If you use electric resistance heaters, consider getting heatpumps.

The cheapest time to upgrade is always when the old system/ item needs replacing anyway.

raytaylor

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#2046821 1-Jul-2018 14:24

I have talked to a number of the local solar installers around here and it seems that on new house builds where they are installing a new hot water system (not retrofitting), then the solar installers are suggesting you go with an electric heat pump based hot water system as you get the 3x the efficiency (because its a heat pump), and can run it during the day on solar.

This makes it more efficient than solar water tubes and cheaper per litre of heated water than LPG/gas, while effectively making the best use of your dump load - more litres heated than a resistive element for the same amount of power fed in.

Solar usually never works out if you take a typical roof and then ask it to heat water using PV and a resistive hot water tank. It does make sense if you have a heat pump cylinder to make better use of the PV, gas so that you dont use the PV at all for water heating, or an evacuated tube panel again so you dont use the PV for water heating. Though with EV tubes you often need to use mains to boost the water temp even though the EV tubes will do most of the work.

In fact if you are just looking at cutting down your power bill, then water is really the first thing you should be looking at in a retrofit before solar PV as water heating is your biggest power consumer.

And gas is not environmentally friendly so should be ruled out. If you do happen to want to be environmentally friendly, stay with mains electricity because 90% of it comes from renewable power.

Ray Taylor

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MichaelNZ

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#2046823 1-Jul-2018 14:28

From what I have read in other online discussions - some people have been unhappy with heatpump hot water heating. Gas is proven to work well thoughout New Zealand and has widespread adoption. I can personally attest it does what it advertises. If you go this route, Rinnai has the best reputation and is Japanese made.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers | ZL2NET

pstar008

362 posts

Ultimate Geek
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#2046825 1-Jul-2018 14:38

Wow, the discussion take detour I never thought of! But looks like PV plan is on hold. Probably sort out the hot water first, might then consider a minimum PV system for a third of my usage to maximum ROI.

Aredwood

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#2046870 1-Jul-2018 15:34

Solar hot water has its own problems. Main one being managing excess heat. I have solar hot water myself, and had numerous problems until I installed a heat dump system. Although solar hot water scales up to larger sizes far better than solar PV.

Heatpump hot water is never as efficient as heatpump room heating. Simply due to the far larger temp rise required. I reckon that a COP of 3 is a bit unrealistic for heatpump hot water.

Gas is actually better for the environment for cooking and other similar tasks that have to be done at peak usage times. As there is still gas, coal, (and sometimes diesel) generation in use at peak times. And it is far more efficient to burn gas in your stove. Than it is to burn it in a power station, turn it into electricity, transport that electricity to your house. Only to turn it back into heat.

Hot water is completely different. As it can be heated with night rate power or solar. Using the cylinder like a battery. And electric hot water can also help power network stability via ripple control.

pstar008

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Ultimate Geek
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#2046880 1-Jul-2018 17:03

I can easily imagine once solar go popular, the electricity provider will figure out a way to make solar user on grid paying more for been solar and consume less electricity, or simply drop the pay back rate.

On the other hand, I did some personal research a couple of years back on electricity generation from a consumer point of view, and looks like New Zealand had very limited options to expending power generation in the future, thus, the cost of generation electricity are unlikely to drop, hence up is the only way. But of course the cost is only a portion what we consumer getting charged.

Aredwood: Electric heating via heatpumps will still be a lot cheaper than bottled gas. And probably still cheaper than piped gas. Still use gas for cooking. As it is very difficult to time Shift cooking. And if there is a power cut, you can still cook.

Hot water via electricity might still be cheaper than bottled gas, if you have night rate power available. Although gas hot water will most likely reduce your power consumption enough, that you will then qualify for the low user plans.

Don't assume that power prices will always rise. My current power price is less than 5c per unit higher than what it was 11 years ago. And some of that was due to the GST rate increase. Also there could be structural pricing changes to how power is billed. Imagine if say daily fees increased to around $5 per day. And per unit costs dropped to half their current price or even lower. Average households would still pay approx the same amount per year for power. But goodbye to savings from having solar panels.

MichaelNZ

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#2046927 1-Jul-2018 17:43

pstar008:

I can easily imagine once solar go popular, the electricity provider will figure out a way to make solar user on grid paying more for been solar and consume less electricity, or simply drop the pay back rate.

It's already happened. I remember when FIT (feed in tarrif) was 17c per unit and solar companies were touting it as a profit making exercise.

In summary here are the options for solar. There is no other viable angle.

1. Get a grid tied system to subsidise what you personally use in real time (ie: if you use power during the day)

-or-

2. Go off the grid. But this won't save you money.

Not Labour Party nor the Green Party not the corporate activists at Greenpeace and SEANZ will do anything for you. In this world self-sufficiency is what you own and control. So be sure of what you are doing, why you are doing it, and whether it's realistic. In terms of assessing the later, the only way to know for sure is to chat about it (as you are doing here) with people who actually have notches on their belts, as opposed to wishful thinking and pipe dreams.

Solar power is one of those things which attracts dreamers and BS artists. But thankfully, the advice on GZ seems to be pretty realistic.

WFH Linux Systems and Networks Engineer in the Internet industry | Specialising in Mikrotik | APNIC member | Open to job offers | ZL2NET

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kotuku4

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Ultimate Geek
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#2047326 2-Jul-2018 11:21

I have solar PV 4.9 kW 20x245w pannels and grid tied 4.8 inverter installed 2013, recently upgraded to a larger 270l hot water cyliner and changed hot water timer to hot water diverter. Very happy with this set up.

I had no idea how much PV to install, and went for as much as I could at the time, probably about 3kW would have been optimal. And you may be able to expand later.

Before I installed I upgraded my house over time, with additional ceiling insultation, heat pump, double glazed windows. Have always been low power user.

I am considering battery storage as cost is dropping, but it is still expensive. And my power bills amount to around five hundred dollars a year with winter use heat pump and some hot water heating, family of five, modest sized house with one bathroom. We do get power trust rebates of around $300 per year which keep the cost down. I really do hate to pay for power, mostly fixed daily and other charges. Off grid is not logical unless you are at a site and have to pay significant money to get power lines or cables installed and connected.

One of the reasons for all of the above is the environment. Return on investment for any solar is hard to justify, with PV it is a long term solution. You have your own power generation, but have paid in advance for your power. Export buy back rates have been slashed since my install. I consider it paid for now.

We don't have reticulated gas in my location, and I would not ever consider gas. I investigated solar hot water and heat pump options, but not happy with the cost or the durbility/ lifespan of the equipment based on advice for several plumbers/ installers.

I have a hobby 12v sytem in spearate garage that I need to make better use of, just for tool charging and a radio. Using old batteries, could use a decent deep cycle battery. Would like to put up a small 100-300w wind turbine just for fun, possibly a vertical axis version. I have an e-bike and tools, not sure if I should get 12v chargers or an basic 12v to 240 volt inverter for charging.

An electric car is on the wish list too.

The power diverter I use is a Paladin, it was cheap and it is not smart. The installer I found usually installers Immersun units for around $1500.

gooki

33 posts

Geek
+1 received by user: 4

#2091449 16-Sep-2018 14:05

Hi, I know this thread is getting a bit old, but thought I'd chip in.

We installed 4.5kw of solar on our roof, 5kw inverter and a power diverter for hot water at the end of August 2017.

In the last 12 months our power diverter, diverted $450 worth of solar power into our hot water cylinder.

Our total electricity saving over the last 12 months is approx $1,000.

Our total system cost was $10,500. However we haven't paid a cent for it yet, thanks to 21 months no interest, no repayments.

My $10,000 has returned $1,700 over the last year by staying invested. Add the $1,000 in free electricity and our total cost is down to $7,800. By the time I have to pay for it, I expect our out of pocket cost to be below $7,000.

This will give us a payback period of approx 7 years.

Hammerer

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#2091469 16-Sep-2018 15:09

Your solar return in some parts of NZ can vary by 25% from year to year. In my locale the sunshine hours have varied by up to 20% from the previous year with a consequent impact on payback periods.

It is good that the overall trend is upwards but his year the sunshine hours for June were up in Auckland and down in Wellington and Christchurch as shown in a graphic in this Herald article: https://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=12081553

Aredwood

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#2091726 17-Sep-2018 02:06

gooki: Hi, I know this thread is getting a bit old, but thought I'd chip in.

We installed 4.5kw of solar on our roof, 5kw inverter and a power diverter for hot water at the end of August 2017.

In the last 12 months our power diverter, diverted $450 worth of solar power into our hot water cylinder.

Our total electricity saving over the last 12 months is approx $1,000.

Our total system cost was $10,500. However we haven't paid a cent for it yet, thanks to 21 months no interest, no repayments.

My $10,000 has returned $1,700 over the last year by staying invested. Add the $1,000 in free electricity and our total cost is down to $7,800. By the time I have to pay for it, I expect our out of pocket cost to be below $7,000.

This will give us a payback period of approx 7 years.

Did you get a quote from a company that doesn't offer finance? As those interest free deals definitely have a cost to the company that you purchased the system from.

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