Premium monocrystalline solar cells using 60-96 cells and N-type IBC silicon, with 335-360W ratings and 20-22% efficiency are the panels to buy and yes, they are the most expensive.
Solar panels lose power generation efficiency over time and due to heat. You will see a much-touted 25-year ‘performance’ warranty on most panels. Read the fine print.
Most panels have 5-10-year manufacturing defects (failure) warranties, but under Australian Consumer Law, the warranty is the installer’s liability. They are frequently not around long enough to honour it.
Then there is the so-called ‘performance’ warranty that panels will still produce say X% of the efficiency at 10 years and Y% at 25 years. Cheap panels might be 60% of the efficiency at 10 years and 30% at 25 years – ditto.
Good panels should have 90% of the efficiency rating at ten years and 80% at 25 years.
To put all that in perspective (using standard 1 x 1.65m panels)
- 10 x 250W cheap panels produce about 2.5kW now and 1.25kW at ten years
- 10 x 360W good panels produce about 3.6kW now and 3.15kW at ten years.
So, if you wanted a 10kW system, you are going to need 40 cheap panels (that will not output 10kW after ten years) or 27 good ones that will.
There is a good overview of panel type here.
What about inverters?
A lower-cost solar only inverter lasts from 5-10 years (usually with a 5-year warranty and about $500 to replace). Many cheap installers use under-sized inverters (ironically called ‘over-clocking’ and they will dazzle you with science saying that is OK). You need perfect-sized inverters.
And battery technology is moving to AC Coupling, meaning that you don’t need a special solar/battery hybrid inverter – just a grid-connected inverter. This is the way to go, and yes, it costs a little more for these batteries but it provides you with redundancy in your energy system. If the battery inverter fails, you still have the solar inverter functioning to keep your bills low while you replace it.
How an AC Coupled battery system works – the example is Tesla PowerWall 2, but there are many others.
My advice – try solar first and add AC Coupling batteries later if Emberpulse shows that you will financially benefit.
Also, beware there are often deliberately hidden costs that the cheap advertisers do not tell you until you have signed up. For example, you will need a smart meter, your main power board may need upgrading or replacement, electricity cabling may need to be rerouted or replaced, and the installation may be difficult needing custom mounting frames.
And you may be convinced to install a more expensive hybrid solar/battery inverter that you may not ever use. All this can add thousands to the cost making payback far longer. My advice, install solar today with a standard, correctly sized solar inverter, ensure the wiring is set up to easily add a battery and separate battery inverter later when the time is right.
Now to batteries
Battery ratings are in kWh – in other words, they can deliver X kW for an hour. Let’s say that is 10kWh or 10,000 watts for one-hour, 5000 watts for two-hours, 2500 watts for four-hours etc. The amount of energy from the battery is also limited by inverter connected and battery type. So, ensure these are performance-matched.
To put that in perspective a 2500W heater (or oven/cooktop) will almost exhaust it in four hours!
kWh are like litres in a fuel tank. Then you need to know how much fuel you use to match your needs. If your house has a V8 power need at night, you may require larger kWh batteries and solar systems to ensure you can both charge the battery enough and have enough storage for overnight usage.