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How quickly do solar panels pay for themselves?


Another one here:

They are partners with Sun Tenants


And here’s another one Digital Solar


We have solar panels. Got them when they cost the earth, but they have almost paid for themselves. We thought it would take about 7 years to repay the cost but it will take about 8. We have less than a year to go. We run two spreadsheets; one records the amount of credit we get from the panels and the other keeps exactly what we generate. Since having the panels we have had to pay a small fee for electricity about twice. That means we are in credit. We are also able to get the higher input payment due to when we had them installed.

We did this because we were just starting retirement and thought it would be a good way to lower our bill.


If you regularly get no bills and only paid for electricity twice in 7 years then they paid for themselves years ago.


Good of you to know without the spreadsheets to know that our solar panels are paid for. I will reiterate they will have paid for themselves in less than a year.


I too am an early solar rooftop adopter paid $10K for a small system 9 years ago and received a government rebate of $8K when they were installed and running so my out of pocket was around $2450 after he extra cost of a smart meter etc was installed.
I do still get a average quarterly bill around $200 but it was prior to the install closer to $350 and without needing a spreadsheet I deduced that they saved me around $600 per year on my previous non solar install power bills and therefore were paid off around year 5.
That is how I can deduce you realistically had them paid off years ago if you have only received a couple of small power bills in 7 years.


Good for you. We didn’t get anything like that in 2011. So your figures don’t relate to us and really you’ve made an assumption.

We actually know how much we have generated in the time as well as how much of it we used and how much we received credit for.


We installed a 10.14kW system on our roof in Canberra nearly two years ago. The feed-in-tariff is insignificant but, based on our electricity bills for the year preceding installation, our system will pay for itself in six years. We are both retired and spend a lot of time at home, and we keep the house liveable 24/7.


In SE Qld, we have had our $14K 5KW solar system for 5½ year, and received just over $7K credit (at 51c/kWh) on our electricity account.

With four of us at home full time using electricity, we export to the grid 23.95% of what we import, with an average of 7.33kWh exported to the grid per day.

If we extrapolate, we can expect the system to pay for itself in 5½ years, for a 11 year cost recovery.


What is the difference?


I was trying to be clear and explaining the figures:
5½ years more to go before we have recovered the cost. A total of 11 years.


It’s got me beat too :wink: If $7k worth of credits have been received and with something like 15kWh/day or more of self consumption, which is esentially free electricity (as in zero marginal cost) instead of paying for grid power, I would think it would be well paid off already.


Choice attempted to answer this question in 2013 , the report is here.

My first question is, given the rapidly changing market, when will these calculations be updated?

My second is about cost trends. In the above report it was said that "the technology is so cheap at the moment. It’s hard to imagine it can stay at this level as it’s not much above the cost price of the gear and the labour costs. " As 5 years have passed has that prediction proved to be accurate?


In April 2016 I bought 16 panels.

In the first year the amount of electricity produced almost exactly matched the amount we used.
Of course the electricity produced is during the day and even though we do as much as we can during the day we also use it during the evening. Consequently, some of the electricity was bought by the WA government.
In WA for normal accounts, we are charged $0.241 per kWh for electricity we buy and are paid $0.07135 per kWh for electricity we sell to the government. For us the financial yield was $884 that year. So on an investment of $6,259 the yield was 14.1%. Not bad because these days it is difficult to get better yields. However, it would mean that (on this basis) it would take seven years to get our money back.
In year two the production of electricity was 4.5% less. Most advice given to us for this was that the panels get dirty and need regular cleaning to keep efficiency up. however, as it would cost me about $150 to have this done then I have to accept the declining performance. So we are looking to get our money back in about eight years. By then hopefully technology will have improved an we can throw these panels away and get better ones.


Why throw them out? They are likely to produce useful output for at least another 20 years. If you need more energy, just add another system or more panels to the existing system if the inverter can handle the extra input.
Did you take into account weather variations to account for the 4.5% reduction in output? The proportion of sunny weather vs overcast could easily account for that difference. In most areas rain is sufficient to keep panels reasonably clean, so long as they are tilted at a sufficient angle.


Let’s hope you are correct. However, I have just checked production for one month in year three (a rather sunny and warm May) and the production has declined from and average of 19 kWh per day down to 9.6 kWh/d. We’ll have to wait and see what will happen but the evidence so far is that the equipment’s production is declining.


A 50% decline in output in 3 years is not normal, assuming your weather has been similar in both comparison months. It indicates there is new panel shading, or perhaps one out of 2 panel strings has no output, maybe due to an isolator problem or corroded connection. Shading of one panel can wipe out almost the entire string’s output in sunny weather, but in overcast weather doesn’t have such a large effect, due to the diffuse light source and lack of dense shadowing (assuming the shadow is not due to something very close to the panel).

What size system is it? How many strings of panels? The inverter should show inputs from each string by scrolling through the menu, and you may be able to determine where the problem is- you need to check several times throughout the day for shadowing issues. Alternatively, if you have decent system monitoring and logging, the problem may be much simpler to pick up.


Hi Gordon

You are right. I was taking these figures from my spreadsheet of the electricity bills.

My view was too simplistic: We have received $7K of credits. The system cost us $14K. So the system was half paid off.

You are right that I didn’t take into account the electricity we used but didn’t export. DUH!


We’ve recently done some analysis on solar payback times exploring the cost of a 5kW solar system and how long will it take to pay itself off.


There’s an amusing anomaly in the NT - an optional ‘switch to six’ plan gives a lower consumption tariff 1800-0600 (overnight) than the FiT and a higher consumption tariff 0600-1800 than the FiT - low tariff applies all weekend as well. So given the occupancy of my home is low to zero during the high tariff rate I’m better off on this scheme using my high consumption devices at night and weekends …

There has also been a lot of schemes and rebates - my payback time on 5Kw is ~2 years at current rates, but that was taking advantage of a significant cash match deal from the Govt …