The answer to that is never going to be easy, there's a lot of variables. It will depend on how much it costs you to install, how large a system you can install, how long the equipment lasts for, and how much your supplier will pay you for the electricity that you generate. And, of course, what the weather is like—suitable temperature and sunlight to generate power, and how much heating or airconditioning you need to use in your home. Solar power works on the strength of sunlight, not heat; their efficiency drops off when the panels get too hot
All of those things will be different for everyone, and it needs to be pointed out that electricity companies want to earn X million dollars a month from their customers. And if they sell you less electricity, they'll just raise their pricing so they can still earn the same amount from you.
This table, below, is how we've fared (I've only included the years I have full data for). I'd estimate that the equipment using electricity in the house has been fairly consistent over most of the years, only tapering off in the last three years. The electricity totals are a sum of the amount we've imported from the network ignoring the amount we've exported (the imported electricity is comprised of two parts—general supply, and off-peak overnight water heating on a time clock at a lower cost, with the amount of our imported electricity being slightly reduced by the small amount of power we've generated during the day). The bill total is what we've had to pay (the cost of supplied electricity usage minus the payment for any surplus generated electricity returned to the grid). The surplus exported is the solar power generated that we haven't used ourselves. As you can see, our system's contribution to reducing the amount electricity needing to be generated by the utility services is very modest.
|Surplus Exported Electricity
|32¢ to 34¢
|15¢ to 19¢
|16¢ to 20¢
|37¢ to 39¢
|17¢ to 20¢
|39¢ to 45¢
|17¢ to 23¢
|45¢ to 56¢
|18¢ to 27¢
|8¢ to 10¢
|56¢ to 59¢
|25¢ to 34¢
|59¢ to 62¢
|30¢ to 36¢
|12¢ to 16¢
|62¢ to 64¢
|29¢ to 37¢
|13¢ to 16¢
|64¢ to 71¢
|27¢ to 35¢
|13¢ to 15¢
|24¢ to 7¢
|16¢ to 14¢
|83¢ to 69¢
|38¢ to 30¢
|22¢ to 15¢
|14¢ to 12¢
The ranges show where pricing has changed during the year, the reasons are that they've changed pricing, and the pricing changes when the amount of electricity crosses various thresholds (they charge you more as you use more, and pay you less as you generate more).
You can see that after we had a $5000 1.7 kW solar power system installed half-way through 2012, the amount of electricity that we've imported from the supplier has gone down, but the amount we've been paying has increased. We were never on a plan where we would be paid a lot for the electricity we generated, that boat sailed away before we got on board. And South Australia has some of the highest electricity costs.
After 2013 the amount of electricity imported went up again. Once you think you have free electricity, you do get a bit cavelier about not having to be so energy concious. And I suspect the system stopped working as well as it could do within a short period of time (that's another problem with home solar power generation trying to be cost-effective, your system has to be free of expensive failures). Then it starts to go down again as you improve your efforts to reduce your electricity usage. However the bills have gone up as they increased the pricing (that's only partially due to inflation, it's mostly due to them wanting more profits), and your only recourse to that is to have a very expensive larger capacity system with battery storage, so you can be self-powered all day and night. And the question is, can you put in a useful system and it be cost-effective? Or to put that another way, can you afford to pay for 10 to 20 years of electricity upfront in one go?
Two thirds through 2018 shows a change in trend after there being one less person living in the house. And with 2020 we've had quite a sunny year, and halfway through the year I replaced the solar hot water system (that wasn't heating water from the sun very well) with a new system of the same capacity.
A modestly priced (or heavily subsidised) system with a reasonable power output may well be cost effective, for some people. But I've never understood why people have installed home systems worth $20,000+ when they're in an area with a mains supply already available. It'd be very hard to recover those installation costs, you're going to have equipment breakdowns (due to age) around the time you're trying to break even, or make a profit. And some of the suppliers have not been shy about saying they wouldn't allow people to turn their solar systems into a money-making scheme.
There's quite a few flaws with promoting home solar power as a panacea. Most people are not home at day to use their self-generated electricity, so the idea of using power-hungry appliances (like washing machines, heating, airconditioning, etc) from your so-called free power isn't practical. The reality is that probably the only power-hungry device using your solar power during the day is your fridge (they use more power than people think about; if you suddenly get a big bill, check your fridge is running properly). We live in an era of there being more and more electronic appliances running in the household, many of them consuming power all the time, even when you're not using them. Most people don't have battery storage, so they're using mains grid power when they're home after work. You need to be paid a decent export rate for your surplus power to offset your grid usage, but they're not being offered any more. And the utility companies put their prices up if their profits go down.
If we wanted to be greener, and using more solar power than fossil fuels to generate electricity, it would have been far more efficient to subsidise adding massive solar power (as well as wind power, and other non-fuel systems) generation capabilities at the utility companies rather than on individual homes. As populations grew and generation demands increased, the utilities should have been expanding their systems with non-fossil fuel systems.
The solar power racket really pisses me off. There's a whole pile of things wrong with how solar power is implemented in this Country (Australia).
The government pushed people into installing it with bonuses being paid to have an installation, and overly generous payment schemes for the electricity you generate were set up, where you get paid more to generate electicity than it costs you to purchase it (e.g. it'd cost you around 22¢ a kilowatt to use electricity generated by the power company, but you could get paid around 60¢ a kilowatt for what your solar power system generated). Now, in 2020, it's around 40¢ a kilowatt to buy electricity, and we're only paid around 16¢ for what we generate.
While that sounds enticing, only 6¢ to 8¢ of that is paid by the power company, the rest of that is paid by the taxpayer. They've bribed us with our own money (yes, taxes are our money, not theirs). So, you're paying yourself to make electricity, and paying your neighbours, and they're paying you. And, if you don't have solar power, perhaps because you can't afford it, you're paying everyone else this without getting any benefit.
The electricity companies are being scabby about paying you just a pittance. Because they claim that's all that it's really worth, once they factor in their costs of maintaining the system (their generators, wiring, et cetera). While completely ignoring the fact that home solar power owners have paid for their equipment, its installation, and will have to pay for ongoing maintenance.
And, of course, now they get less money from their customers, they've pushed up their prices, because they're interested in making x millions of dollars, and don't ever want their income to drop.
Never mind that for many years, some of them have been arguing for the right to be able to turn off your appliances, because they say we're using too much electricity for them to be able to generate (such as during summer, with everybody's air conditioners running), because they can't be arsed to adequately update their generating capability as the population has increased, and electricity usage increased as a result. We've had decades of power problems due to inadequate power supplies from the power company, they've persistantly mismanaged that situation, and persistently told us to use less power rather than generate an adequate amount.
There is a flaw in the electricity supplier's arguments about us burdening the supply too much with our airconditioning: Electricity use during the day (by business and industry) is far greater than home usage after business hours. And most people are at work during the day and not using their home airconditioning. And oddly, the suppliers only ever whinged about airconditioners using too much power, they never moaned about heating (which typically uses more power than cooling).
As far as I'm concerned, we should be paid the same amount for the electricity that we produce, as what we pay for them to generate, per kilowatt. We wouldn't have had to have the meters changed over, to have separate accounting for incoming versus outgoing power. Nor have all these complicated pricing schemes. Nor have to put up with the power company's scams of demanding you pay them quarterly, while they'll only pay you anually. It should simply work one way or another, crediting you or debiting you the same amount, for how many kilowatts went through the meter, depending on whether you generated more power than you used, or vice versa.
Written by Tim Seifert on 29 Sept 2012, and last updated 19 Feb 2021.