Grid connect solar problems – what vendors may not reveal

by | Aug 1, 2020 | Articles, Household Solar, SS

Grid connect solar problems

Grid connect solar problems include, false promotion and vendor claims, incompetent installation etc. Here’s what vendors may not tell you.

Q. Must solar panels be at an exact angle?

A local installer says my existing 1.5 kW system’s modules must be at exactly the same angle as my latitude. They are only a few degrees out). He say he can fix them for $1000 – so most days they’ll produce a lot more. Is this a scam?

A. Yes. He’s after your money!. In most areas plus/minus 5º makes less than 1% or so change. It may, however, result in a bit more in summer than winter – or vice versa. Less than that will make next to no change. It is, however, desirable to have them face more or less into the sun around midday. But, here again a few degrees does not matter.

Q Grid connect solar problems – do I need after-sales service?

My installer seeks $250 a year for ‘servicing and tuning’ my 1.5 kW grid connect system. Do I really need that?

A. This too is a scam. Installed solar needs no servicing, let alone ‘tuning’. Unless the modules are truly dirty, there is likewise no need to clean them. Occasional rain does the job. Our own grid connect systems (north of Sydney) remains unwashed since 2010. There is no measurable loss.

Q. Grid connect solar problems – do I need a tracking system?

I live in the south of Australia where the sun is much ‘lower in the sky’ in winter. My installer advise using a $5000 (plus $1000 installation) tracking system for my proposed 1.5 kW grid-connect system. He claims it will save the amount of solar capacity otherwise needed by about 30%. Is this true?

A. What he claims is true. But what he has not revealed is a lot!

Tracking systems are costly and need ongoing servicing. It is hugely cheaper to accept that loss. You can add another 450 watts more solar capacity for a probable $1250! And zero maintenance.  Find another installer.

Q. Grid connect solar problems – how do I work out the grid-connect size I need?

I’d like to install enough grid-connect solar to halve my existing power bill. Installers say they need to calculate how much electricity is used and quote accordingly. Is there any way I can tell if they are selling me more than I need.

A. This is routine practice. The best way to start, however, is to reduce existing usage. We slashed the previous owner’s 31 kWh a day to 4.1 kWh a day summer and 6 kWh in winter.

It costs some money up front, however, savings are huge over time. That alone will fix that ‘halving’ you seek. Adding solar then – and only then, will drop it yet further. It is not feasible to explain how in an article. The first third of my book Solar Success shows exactly how to do it. It includes actual examples (including our own). Unless you do this, the installer will scale the system to existing usage.

Q.Grid connect solar problems – is it true that most grid-connect system produce less than claimed?

My 2.4 kW grid-connect solar system has only produced the claimed input twice (for a few hours) within a now five years. The most I get is 2.2 kW. It’s often less. Should I ask for a rebate?

A.  Solar module reality is, to put it mildly, curious. It can only produce the promoted output under laboratory conditions. Such conditions do not replicate typical usage. The output you have is typical.

A solar module’s output in typical usage is shown in makers’ technical literature. It is even revealed on the back of most solar modules (but out of sight once installed.) It can be seen (below). The test laboratory claims (also use for promotion!) are in column 2. The ‘real-life’ output is that in the third column. Here, a nominally 120 watt module is shown as having a typical output of 87 watts.

Solar warning

As seen in the above example, the most probable output of this solar module is ‘120 watt’ solar module is 87 watts. That 47 degrees C is not ambient temperature it is of the cells under hot glass.

I do not know of anyone taking legal action re this. But all installers I have discussed this with agree my statement is correct. Their installation reports (needed for rebate claims) often reveal that ‘true’ output. My own does.

Q. Grid connect solar problems – optimising tariff rebates

My 2.4 kW grid-connect solar system about 7 kW hours/day in winter, and about 15 kW hours/day in summer. Our home uses about 21 kW hours/day year round (we have gas heating). The rebate only cuts our electricity bill by about $100 a year! Is there anything I can do about this?

A. The enquirer and her partner are away from home all day. They currently pay 27 cents per kW hour during the day, and 67 cents per kW hour during the evening. They export almost all they generate for a few a unit, and pay 67 cents per unit for virtually all they use.

Most electricity companies, however have a flat rate. This is typically half the peak rate. Switching to that alone halves their bill. More can be saved by programming the dishwasher to run at about 11 am. Likewise the washing machine at about 1 pm. (See also below.)

Q. Grid connect solar problems – time shifting energy input

As I use most electricity at night, is it worth adding battery back-up to my grid-connect solar system.

A. Some grid-connect systems have in-built provision for this. If not it’s possible but costly.

Another approach is independent mini-systems, each of a small battery charger and battery, plus a stand-alone inverter.  This is legal in Australia providing the inverters are ‘stand-alone’ units with one or more outlet socket/s. Appliances plug directly into the inverter (via a multi-outlet power board if desired). Use only ‘electrically isolated’ inverters.

The grid acts as a ‘virtual battery’ for short term high current loads. Run these close to midday via their time switches. That enables them to run from solar power otherwise exported and paid for at a low price. My book Solar Success covers such issues in depth.

The electrically knowledgeable can legally do this themselves. No installation is required so cost is low.

Such inverters must absolutely NOT be connected in any way to 230 volt mains fixed wiring.
Inverter jaycar mi5704

Appliances (230 volts ac) may be legally plugged directly into stand-alone inverters such as this 12 volt 800 watt unit from Jaycar. Pic: Jaycar.

Q. Taking grid-connect totally off-grid – is it worth doing?

I have a 3.6 kW grid-connect system. On most days I have more input than I use. Is it worth disconnecting from mains (grid) power so it becomes a stand-alone (battery) system?

A. You can do this, but it currently only makes financial sense if you are paying over $1.30 a unit (a unit is 1.0 kW hour). It also necessitates installing an inverter made for stand-alone use.

Right now it makes more financial sense to retain the mains (grid) supply for cooking and heating etc (as a virtual battery). Use use solar and a battery bank for semi-continuous and continuous light loads, like refrigeration, entertainment, computer, and LED lighting etc. The approach suggested above is a better solution financially for some years yet.

Q. Can a grid-connect system produce peaks in excess of that claimed?

I have a home very close to the sea. Sometimes the output shown on the energy monitor jumps to way over the claimed system output (but only for a few minutes). How is that possible – and what causes it?

A. This can indeed happen. It is, as you say, usually for only a very short time. It adds only a little to the daily input and occurs where a nearby surface is reflective (as an expanse of water or light sand). Sunlight is received directly by the solar modules, but some is then reflected upward from that nearby surface. If there is light white scattered cloud, that cloud may then reflect that energy down again such that it is received again by the solar modules. The increase may be as high as 20%-35% but there is usually no real gain as the scattered cloud also reduces solar input from time to time.

The solar array (above) on the roof of the author’s home at Church Point, NSW, has the effect described above. Sunlight is reflected back up from Pittwater – about 50 metres away.

The issues raised here, plus many more, are covered in depth in the author’s book Solar Success. It sells globally and has literally saved buyers thousands of dollars on their installations. My book Solar That Really Works relates to solar for cabins and RVs. My other books are the all-new Caravan & Motorhome Book, Caravan & Motorhome Electrics, and the Camper Trailer Book. For information about the author please Click on Bio.

Collyn Rivers is a semi-retired automobile research engineer.  He is the author of seven books, five of which are about making RVs and solar work optimally.

Solar Success

Whether you’re building a new home or adding solar to an existing structure, this is the one book you can’t afford to be without.

eBook versions

Paperback version

Any bookshop, whether online or bricks and mortar, can order copies of Solar Success.  Just ask.
ISBN: 978-0-6487945-4-7

Solar Success

Whether you’re building a new home or adding solar to an existing structure, this is the one book you can’t afford to be without.

eBook versions

Paperback version

Any bookshop, whether online or bricks and mortar, can order copies of Solar Success.  Just ask.
ISBN: 978-0-6487945-4-7