worthwhile for extra tilt cost on 5deg roof?bris

[ls_leong]

I am trying to work out whether it is worthwhile to pay the extra money to tilt solar panels on my roof.

I am looking at getting 11 x 225wSuntech panels, with German SMA inverter =2.475kw system (grid connected).
Cost of system = $7598 installed after all rebates/RECS etc (and includes $100 for extra 10m cabling/ conduit and $185 for meter isolation links, which they said I needed after coming out to look at my roof/meterbox, and 2 storey house extra safety costs of installation).

Cost of aluminium tilts would be additional cost of $1622 to withstand 240km/hr winds= total system cost $9220

I live in Brisbane(ideal roof pitch apparently 27deg), and have a large almost flat completely unshaded northeast facing roof, tin construction, 50 yrs old, which has 5 deg pitch which the installer measured. (Is an unusual slight inverted V shaped roof with a box gutter, but essentially roof space of that orientation is not an issue)

I use 12.5kwh/day at the moment , with electric hot water and electric stove. I am also going to get solar hot water, so expect my energy use will reduce a bit more.

The sales guy told me that with lattitudes above byron bay, the energy loss by not having tilt is small and would take 16 yrs to cover the cost of the tilts.
Other solar guys I have spoken to have said that the dust can accumulate at that level of tilt and its worth paying for tilt.

My other concern is storms and the system being ripped off the roof (though my suncorp ins. does cover panels)

Also the other additional cost is the electrician thought my meter box may have asbestos and might have an extra cost for energex to fit the meter. Has anyone just bought a new meter box to house the new meter and connect to the old box or a box to house the new meter and the inverter (is very much under cover under verandah).

(my main aim in going solar is the cleaner energy side of things, as hoping to set the house up in a very sustainable way)

Any advice would be very much appreciated.
Louise

[francisscott22]

At first it can really be costly. It's more like an investment for the long time ahead and being earth friendly.

[c*p]

Hi Louise. The old cost-benefit analysis. At a tilt of 5deg NE, your system would produce about 92% of what it would produce if tilted at the optimum angle (you're correct at about 27deg) true North (reference: CEC (Clean Energy Council) PV System Design Guidelines). In fact, with such a low tilt of 5deg, there is little difference in performance up to about 70deg away from North. I am not sure of the effect of such a low tilt reducing the self-cleaning, which underpins the recommendation that panels are tilted typically more than 10deg. If you are energetic, you could check the self-cleaning by investigating how dusty or dirty your roof is. Try cleaning a small area. How much cleaner does it look? How dirty is the water and cleaning cloth? Are you up to occasionally cleaning your panels if you decide the self cleaning at 5deg is not sufficient?

Another consideration is that tilting BELOW the optimum angle increases the SUMMER output, but reduces the Winter output by a bit more, hence the lower overall output. If your panels were tilted ABOVE the 27deg optimum, then you would increase the WINTER output. Thus if you use more power in Summer relative to Winter (by airconditioning, for example) the lower tilt is better for power-balancing. If you want to maximise your export of power, to get the biggest feed in benefit (but I am not sure what power contracts are available in Brisbane), then you seek to make your panels produce most when your usage is least.

What is the cost of the power difference?
By the CEC Consumer Guide, a 2.5kW system in Brisbane will produce about 10.5kWh per day on average. With usage reductions by going to solar hot water, and possibly other efficiency measures (gas stove?), you will come close to netting off your electricity usage. The 10.5kWh/day is about 3,800kWh over a year. By not tilting your panels, you will lose about 8% of this output, or about 300kWh. So how much does 300kWh cost you? This depends on your supply contract. At 35c/kWh, a typical peak rate (in Melbourne), this is just over $100. If it all (an extreme assumption, not likely) comes off your possible export of power, at 68c/kWh (Premium Feed In Tariff), the cost is a bit over $200.

Another option to compensate for not tilting, might be to simply buy an extra panel, if your inverter can manage this. You'd have to check with your installer. Buying 12 panels instead of 11 represents an increase in system size of about 9%, which more than offsets the decrease by not tilting. The cost of the extra panel might be $800 or so, plus a bit of additional framing ... again, you'd have to ask your installer about this. It may well be cheaper than the tilt framing, less subject to storm, and possibly more aesthetic. c*p