We’ve finally bought our solar system

We refined our load list, and got the load down to 21 kWhr usage in winter (assuming the tropical fish come with us – when they’re gone, we should be down to 16 kWhr!), and went out for quote.

We got four quotes – one from a local solar company, who mainly do rooftop solar, but have done some off-grid, and 2 companies that specializes in off-grid, and one large company that does a lot of things, but bought up a local solar company. Happy to give names if interested.

In preparing the list, I did not put in our full planned summer usage – from previous experience, when we did, the indicative quotes gave us way more batteries – their sizing is based on a certain percentage of power being used overnight. Since we do not plan to use the AC at night, I did not want its use in summer to increase the battery size, so left it out to make things easier.

	Vendor 1	Vendor 2	Vendor 3	Vendor 4
Solar panels	36 x 370 Jinko Solar Tiger TR	36 x 370W Winaico	31 x 390 W Hyundai	60 x  345W JA
Solar Inverter	2 x SMA SB6.0	1xFronius 8.2.1 & 1x Fronius 3.0.1	1 x 802 kW Fronius	2 x 8-2.1 kW Fronius
Battery Inverter	2 x SMA SI8.0H	Selectronic SP PRO SPMC482	Selectronic SP PRO SPMC482	2 x Selectronic SP PRO SPMC482
Batteries	2 x BYD Premium LVL 15.4 (30.4kWhr)	2 x BYD Premium LVL 15.4 (30.4kWhr)	Power Plus Eco (28kWhr)	2 x BYD Premium LVL 15.4 (30.4kWhr)
Generator	10kVA Blue Diamond silenced diesel	Not offered. Will wire in.	10kVA PR Power	Not offered
Price	$70k	$73k	$68k	$97k

While Vendor 3 (large company) was the low bid, we discounted them immediately. They designed the system, according to their documentation for 20 kW, hence the lower number of solar panels, and less capacity in the solar inverter. They also selected the Power Plus Eco battery, rather than the Power Plus Premium. The Eco batteries are warranted for 60% capacity after 10 years, vs 80% for the Premium. So that wasn’t any good either. It all would have required upgrade. The generator has a Kubota engine, so that was good. They picked quality suppliers, but then shortchanged to produce a low bid. Don’t like the tactic – it might fool some people.

Vendor 4 was a last minute inclusion after I’d read good things about them on line. They didn’t want a load list, just talked to me on the phone, and then came up with their bid – very odd. 20kW system, instead of 13kW. So obviously loads more expensive. I found the experience a little patronising, so discounted them. We certainly would have been happy with the system, just not the cost. And it wouldn’t have fit on the shed.

Vendors 1 & 2 were the folk who I had got my indicative quotes from when we were planning the house. Vendor 2 is really knowledgeable and specializes in off-grid. After some discussions, they did reconfigure the system with different panels and a few other mods to come in at a lower price than Vendor 1, but that was without the generator, so still around $5k -$10k more expensive overall. The gear they proposed is arguably better quality, so you could see where the money went.

But ultimately, the question was, was Vendor 1 equipment good enough? The Selectronic, from what I can see is pretty much the best you can get – it copes with supplying power surges better than anything else, has a great warranty and is Australian. The Sunny Island is good. Sunny Boy vs Fronius? Both good. Winaico generally rated better than Jinko, but Jinko OK.

What I really liked about Vendor 1 was that we had two solar inverters and two battery inverters – no single point failure. One of the inverters dies, and we may need to cut back our power usage a bit, but all the essential services are still going to work. And the equipment was all good quality, right up there, just not quite the best, from my research on line. And of course with 12 kW in each inverter set, without even looking at surge capacity, we should not have any constraints on simultaneous use of appliances.

The Power Plus LiFe Premium are arguably the better batteries, and somewhat simpler since they don’t need a BMS, although the Battery Test Centre did have some trouble with them. But, again likely to have added cost, so we elected to stay with the BYD.

Was local support worth anything? If they were just a one man band, I would say it was a negative – if you have a problem while he’s on holiday, you’re in trouble. But they have a couple of offices and are big in the area so we’re not relying on one person. So local is a plus. We took references from some folk they had installed offgrid system for and they were glowing. So not just well-reputed for rooftop solar.

The generator from Vendor 1 could be an issue. I’d have liked a Kubota engine or similar, but they were upto $8k more expensive, when I got separate quotes. We decided it was worth saving the money – we really shouldn’t have to use it much, if at all (particularly once the fish go). We’ve actually bought a cheapy 8kVA petrol generator to provide power to the tradies building the house, so if push comes to shove – a backup for the backup…. We didn’t want the tradies to use the diesel – running a diesel generator on low load for a prolonged period will destroy it. And we don’t want to install the whole system until just before we move in, because of insurance issues with no one living on site. A cheap petrol generator (trade spec) is much cheaper than insurance.

So, with one mod, we opted for Vendor 1. We’ve actually gone for fewer, larger Jinko panels – the warranty is only 12 years instead of 20, but it means we can get another 5kW of panels onto the shed roof, and save $1k. And in 12 years, who knows what solar panels will look like – but I’m sure they’ll be cheaper and better than now.

We want the expansion space, so we can add panels to charge our future electric cars…. And of course, the generator will be redundant then because we’ll use the cars as backup batteries.

So nice to have finally decided and placed the order. I’ll know hopefully in about 6 months how it all works.