PV payback time and whether to upgrade

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Re: PV payback time and whether to upgrade

Postby ads » Wed Jun 11, 2014 6:23 pm

Just an update on my inverter. It's an SMA 1700, which I'm guessing is rated for 1.7kW. That means I could probably overload it a bit with a 2kW system (replacing the Kaneka panels with new panels and keeping the inverter). Then after the feed in tariff ends I could upgrade further if I wanted to by adding a new inverter and more panels.
3.12kW grid connect PV system (REC 260s, SMA 1700). Half N, half tilted west
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14,000L rainwater tank
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Located near Fremantle, WA
Blog: http://sustainaburb.blogspot.com.au/
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Re: PV payback time and whether to upgrade

Postby Benny » Fri Jun 13, 2014 1:14 pm

I guess it depends on your motivation/plans ads.
If you have spare cash and want to generate as much PV power as possible, go for it - the more PV generation the better for the environment.
We don't use much electricity <8u/day - although that will go up a lot now we have an electric car. I was thinking of leaving the current system as is until the 40c FiT runs out, then just change the whole system over to say a 5kW system. Maybe storage will be a reasonable price by then ? I thought I should try to get a reasonable life of use out of the current panels as I think it might be hard to sell them. Maybe donate to a school or something with big roof area - but then the cost of installation might not make it worth while ?
Have you done any kind of economic analysis ? How much extra will you get/earn from the extra 500W vs the cost of purchase + installation ?
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Re: PV payback time and whether to upgrade

Postby ads » Fri Jun 13, 2014 1:36 pm

My main motivation is that I don't want to be paying big bills when I'm not earning money down the track, plus the environmental reasons too.

We use about 5.5kWh a day on average BTW, so we're fairly low users.

Re economics I've found out the following:

I can keep the FIT as long as I use the same inverter.
I can overload the SB1700 inverter with 2.8kW of PV, some facing west and some north.
Total installed cost will be about $2,500 after rebates.
The system will generate 2MW more per year than the current system.
2MW with FIT is about $1,000 a year, so payback in 2.5 years.

I think it's better economically to change the system now whilst I can get the FIT since it reduces the payback time drastically.
3.12kW grid connect PV system (REC 260s, SMA 1700). Half N, half tilted west
Solahart thermosiphon solar hot water, 180L
14,000L rainwater tank
Greyflow grey water system
Located near Fremantle, WA
Blog: http://sustainaburb.blogspot.com.au/
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Re: PV payback time and whether to upgrade

Postby Benny » Fri Jun 13, 2014 6:14 pm

Thats good thinking ads and I agree with your calculations.
Have you thought about how the N and W arrays will connect in to the inverter ? Does it have 2 MPPT trackers ?
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Re: PV payback time and whether to upgrade

Postby ads » Fri Jun 13, 2014 6:19 pm

I'm not too sure about the technical points. I've just been told by someone who knows that 2 strings of 7x200W panels will work with that inverter.
3.12kW grid connect PV system (REC 260s, SMA 1700). Half N, half tilted west
Solahart thermosiphon solar hot water, 180L
14,000L rainwater tank
Greyflow grey water system
Located near Fremantle, WA
Blog: http://sustainaburb.blogspot.com.au/
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Re: PV payback time and whether to upgrade

Postby davidg » Fri Jun 13, 2014 9:17 pm

ads wrote:I've just been told by someone who knows that 2 strings of 7x200W panels will work with that inverter.

A bit more to it, but put simply though , yes it will work..
Hybrid & Off-grid Systems - You could store Sun to use later- I Do!
SELECTRONIC SPMC-482 7.5kW, 7.2kW's of Arrays

with AC-Coupled Grid-Connected Inverters,
1100Ah 48V Bank

Auto Backup Genset
PVOutput Stats

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Re: PV payback time and whether to upgrade

Postby ads » Tue Oct 21, 2014 1:40 pm

Just an update on this topic. I sold the old Kanekas for $900, a great price for 1.1kW (bought by someone who needed the same panels to upgrade his own system).

Then we had 12 * REC 260PEs installed, 6 facing west, 6 facing north. That's 3.12kW on the SMA 1700. It's all working well and the payback time should be around 2 years (cost $4,600 including removal of old panels). Then we'll have 4 more years of FIT until we go back to the reality of getting screwed for power fed to the grid. Even then we should still have negative bills (credits).
3.12kW grid connect PV system (REC 260s, SMA 1700). Half N, half tilted west
Solahart thermosiphon solar hot water, 180L
14,000L rainwater tank
Greyflow grey water system
Located near Fremantle, WA
Blog: http://sustainaburb.blogspot.com.au/
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Location: near Fremantle, WA

Re: PV payback time and whether to upgrade

Postby ads » Tue Oct 21, 2014 2:08 pm

My payback calcs were wrong in the last message. Assuming an extra 2MW produced per year at 50c/kWh is $1,000 a year. Payback will be around 4.5 years. The higher price compared to my original quote was due to extras: removal of old panels, new racks, new conduits, tilts for west facing array, pricier panels, 2 extra DC isolators.

Another bonus was being able to relocate our SHW system higher up the roof to give less winter shading.
3.12kW grid connect PV system (REC 260s, SMA 1700). Half N, half tilted west
Solahart thermosiphon solar hot water, 180L
14,000L rainwater tank
Greyflow grey water system
Located near Fremantle, WA
Blog: http://sustainaburb.blogspot.com.au/
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Posts: 33
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Location: near Fremantle, WA

Re: PV payback time and whether to upgrade

Postby Benny » Tue Oct 21, 2014 3:01 pm

Good work ads. I see you're in Freo - so you're sure that as long as you don't change the inverter you keep the 50c FiT here in WA ?
Have you checked to see if you have any clipping on the inverter ? If I could get $900 for my 1.5kW Kaneka array I might do the same thing although I only have a 1.5kW SMA inverter and installation might be more as its a 2nd storey roof.
Be interesting to see if any automatic routines at Synergy pick up your extra generation - or did you tel them all about what you were doing ?
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Re: PV payback time and whether to upgrade

Postby ads » Tue Oct 21, 2014 3:22 pm

I'm pretty certain that I keep the FIT, I'll let you know when I get my next bill. I doubt Synergy will pick it up, it will be interesting to see if they come to check on the inverter though...

I assume there will be clipping, but I don't have any way to measure this really. All I do is take weekly readings of the meter and inverter and chuck it in an Excel spreadsheet, fairly basic. If you check my blog every now and again I'll be posting some results on there, probably in 12 months for the new array.
3.12kW grid connect PV system (REC 260s, SMA 1700). Half N, half tilted west
Solahart thermosiphon solar hot water, 180L
14,000L rainwater tank
Greyflow grey water system
Located near Fremantle, WA
Blog: http://sustainaburb.blogspot.com.au/
ads
Solar Fanatic
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Posts: 33
Joined: Thu Sep 23, 2010 3:43 pm
Location: near Fremantle, WA

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