Why Your Solar Isn’t Covering Your Power Bill (and the Upfront-Cost Trap to Avoid)
If your solar isn’t covering your power bill, it usually comes down to one of three things: the system was made too small to keep the upfront price down, you are exporting cheap power by day and buying it back expensive at night, or your household simply uses more electricity than the panels were ever sized to produce. The good news is that all three are fixable, and once you look at the full 25-year return rather than the day-one price, solar in Adelaide still stacks up strongly.
This guide walks through why the bill is still arriving, the upfront-cost trap that quietly undersizes so many systems, and the real return on investment of solar from the first payment through to the end of its working life.
The upfront-cost trap: why “cheaper” often costs more
When the sticker price feels too high, the easy fix is to buy a smaller system. It saves money today, but it is the single most common reason a home’s solar never covers its bill. A system that only ever produces a fraction of what the household uses can only ever offset a fraction of the bill, no matter how sunny Adelaide gets.
The 6.6 kW system that was the default for years is now often too small for a modern Adelaide home running reverse-cycle air conditioning, electric cooking, a pool pump, working from home and maybe an EV. For many families a 10 kW or larger system has become the sensible starting point. Going small to save a few thousand dollars up front can cost you far more in unmet bills over the next two decades.
“Daytime solar feed-in tariffs are racing towards zero. In some places, they already are.“, Finn Peacock, founder of SolarQuotes
You are exporting cheap and buying back expensive
Here is the part that surprises most homeowners. In South Australia there is no government-set feed-in tariff. Retailers set their own rate, and in 2026 it sits at roughly 5 to 8 cents per kWh, with some plans drifting lower. Meanwhile the power you buy back from the grid in the evening costs around four to six times that.
Your panels produce the most at midday, but your home uses the most after dark when everyone is home, the air conditioning is running and dinner is cooking. Without a battery, you sell that midday surplus for a few cents and rebuy it at night at full retail price. That gap is exactly why the bill keeps coming even with panels on the roof.
| What you do with a kWh of solar | Roughly what it is worth (SA, 2026) |
|---|---|
| Export it to the grid (feed-in tariff) | ~5 to 8 cents per kWh |
| Use it yourself as it is generated (self-consumption) | ~25 to 45 cents per kWh avoided |
| Store it and use it at night (battery) | ~25 to 45 cents per kWh avoided in the evening peak |
The lesson is simple: every kWh you use yourself is worth several times more than one you export. The aim is no longer to sell power to the grid, it is to use as much of your own as possible.
Right-sizing: matching the system to your home
The fix for an undersized system is to size it to your actual usage, not to a price point. Energy.gov.au recommends sizing your system around how much electricity you use and when you use it, because the value is in self-consumption. Pull out your last few power bills, look at your daily kWh and the shape of your usage, and size from there.
| System size | Relative upfront cost | Typical SA generation | Best suited to |
|---|---|---|---|
| 6.6 kW | Lowest | ~26 to 30 kWh per day | Smaller home, modest daytime use |
| 10 kW | Higher, scales with size | ~40+ kWh per day | Family home, AC, working from home |
| 13 kW+ | Highest | ~52+ kWh per day | Large home, pool, EV charging |
Generation is indicative for Adelaide conditions. Always confirm sizing against a real quote for your roof, retailer and usage.
A larger system also produces more in winter and on cloudy days, when a small system can fall short exactly when you need it. And because the federal STC rebate scales with system size, a bigger system is not as much more expensive as the panel count suggests, which is why we usually steer customers away from buying too small.
Add a battery to close the night-time gap
If the problem is paying full price for power after sunset, a battery is the direct answer. It stores your cheap midday surplus and runs the house through the evening peak instead of the grid. With feed-in tariffs so low, that stored energy is now worth far more to you than exporting it ever was.
Batteries used to be hard to justify on price. That changed with the federal Cheaper Home Batteries Program, which from 1 July 2025 takes roughly 30 per cent off the upfront cost of an eligible battery (around 5 kWh to 100 kWh). The program was expanded in December 2025, and the rebate steps down over time from 1 May 2026, so the discount is most generous now.
“Adding the battery to the household helped add about $900 of savings each year.“, Dr Saul Griffith, co-founder of Rewiring Australia
The real ROI: from first payment to end of life
This is where the upfront price gets put in perspective. Solar is not a purchase, it is an investment with a payback date and then a long tail of free returns. South Australia has the fastest payback in the country because we pay some of the highest electricity prices, so every kWh you avoid buying is worth more here.
| Stage | Timeframe | What happens |
|---|---|---|
| Upfront investment | Year 0 | You pay the net cost after the STC rebate (and the battery rebate if fitted) |
| Payback | ~3 to 6 years (SA) | Bill savings repay the cost of the system |
| Free returns | Years ~6 to 25+ | The system keeps generating; panels still produce around 80% or more of original output at 25 years |
| One mid-life cost | ~Year 10 to 15 | Budget once for a single inverter replacement |
Quality panels carry a 25-year performance warranty and degrade only about 0.5 to 1 per cent a year, so they are still doing real work decades in. A well-sized SA system delivers substantial annual savings, which is why typical returns on solar land in the range of 10 to 18 per cent. Put plainly: pay it off in around five years, then enjoy roughly two more decades of largely free power. The expensive choice is the undersized system that never pays you back properly.
How T&K Airpower fits in
Solar lives or dies on getting it right from the start, which is exactly why we supply and install solar and battery systems for Adelaide homes. As licensed local electricians, we size your system to your actual usage rather than to the cheapest sticker price, handle any switchboard upgrade and safety and compliance work the install needs, and wire it all to perform for the full life of the system. Because we also look after your air conditioning and the rest of your home electrical systems, we see the whole energy picture, not just the panels on the roof. We are big believers in getting the electrical foundations right so your investment actually pays you back.
Frequently Asked Questions
Why is my power bill still high even with solar?
Usually because the system is too small for your usage, or because you export cheap midday power and buy it back expensively at night. Right-sizing the system and adding a battery to lift self-consumption are the two biggest levers. Reviewing your last few bills shows which one is hurting you most.
What size solar system do I need?
Size it to your actual electricity use, not to a price. Look at your daily kWh from recent bills and when you use power. A modern Adelaide family home with air conditioning and an EV often needs 10 kW or more, where a 6.6 kW system was once the default. Always confirm with a tailored quote.
How much does solar cost in South Australia?
It depends on system size, your roof, the components and whether you add a battery. The federal STC rebate brings the upfront price down, and larger systems cost more but generate proportionally more, so the cheapest option is rarely the best value. The honest answer is to get a written quote based on your usage, which our team is happy to provide.
Are home batteries worth it now?
With feed-in tariffs in SA down around 5 to 8 cents and the federal Cheaper Home Batteries Program taking roughly 30 per cent off the upfront cost since July 2025, the case is far stronger than it was. A battery turns your cheap daytime surplus into evening power, which is where most of the savings now sit.
How long do solar panels last?
Quality panels typically carry a 25-year performance warranty and keep producing beyond that, degrading only about 0.5 to 1 per cent per year. The main mid-life cost is usually a single inverter replacement at roughly year 10 to 15.
What is the payback period for solar in Adelaide?
South Australia has among the fastest paybacks in the country, commonly around 3 to 6 years, because our electricity prices are high and self-consumed solar offsets them. After payback, the system keeps generating for another two decades, which is where the strong lifetime ROI comes from.
Does T&K Airpower install solar panels?
Yes. We supply and install solar and battery systems for Adelaide homes, and as licensed local electricians we also handle the switchboard, safety and compliance work the install depends on. Give us a call on 08 8296 7888 or contact us for a system sized and quoted around your actual usage.
Ready to make your solar actually cover the bill?
If your solar isn’t covering your bill, or you are weighing up a new system or battery and want it sized and installed properly, our team is happy to help. Call T&K Airpower on 08 8296 7888 or contact us online for straight-talking advice and a quote built around your usage.
T&K Airpower has kept Adelaide homes comfortable since 1996. As authorised warranty agents for Mitsubishi Electric, Temperzone and Hitachi, our licensed, repair-first team brings the same careful, no-pressure approach to solar, batteries and the electrical work behind your energy upgrades.
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