Common sense is telling me to try to do things like vacuuming, laundry and cooking at times of maximal sunlight during the day so that more of the electricity I use comes from solar power generators rather than from sources like coal.

Does anyone have any ideas about how somehow quantify how beneficial (or not) this approach is? I'd like to also take into account that doing energy-intensive activities during the evening may increase peak load that is largely going to be met by non-renewable energy sources.

If the benefit is quantifiable it may be easier to convince others to do the same. It may also tell me that this idea is actually rather pointless.

  • Where do you live? Do your friends often get up in the middle of the night to vacuum?
    – Aron
    Commented Jul 19, 2014 at 6:57
  • I guess you're in Australia from your boinc site, but it would be useful to know if that's correct, and ideally which state you're in as that makes a difference.
    – Móż
    Commented Jul 19, 2014 at 12:02
  • Yep, good detective work, I'm currently living in Sydney.
    – eug
    Commented Jul 20, 2014 at 2:15

3 Answers 3


In the purist sense of "the electricity I use was actually generated by a wind farm", your idea is broadly correct. However, unless you actually have solar panels or a wind turbine on your house, that's not how the system actually works.

Broadly, all the electricity generators feed into the national grid (which in Australia covers only Qld-NSW-Vic-SA, but that's 90% of the population). From the grid power gets distributed to whoever needs it and there's a lot of fussing to make sure it all works correctly. But one thing that doesn't happen is segregation of renewable energy to renewable energy customers. Then everyone has an electricity meter, and different retails compete to be the one who bills you for what you use. They buy generated electricity and it's metered on the way in, and they have to balance that against the electricity that they sell. It's no more direct than that.

Think of it like a communal water tank - there's a well, some rooftop collection and a creek all feeding into one tank. Then everyone draws water out of it. If you add your rooftop to the collection there will be more rainwater in the tank and less river water, but there's no way for you to draw just rainwater out of it. The electricity grid works the same way.

Then how are you "broadly correct"? What you shifting your electricity demand to daytime does is push up demand during the day, and reduce it during the night. This does mean that you're helping a tiny bit to push demand towards daylight hours, making solar more suitable. Unfortunately, only a tiny bit unless you get a big campaign going so thousands of people do the same thing. Which doesn't mean that it's pointless, any more than any other single action you can do is. Especially since the cost of doing it is pretty low - a small amount of effort on your part. But it's a small step and most electricity still comes from fossil fuels.

But there are better ways.

If you don't have PV panels, the way to make sure you're using renewable energy is to pay for it. Almost everyone in the first world has the option of paying a little extra on their power bill to get renewable electricity. We chose our electricity provider specifically because they have a "100% wind power" option (and they're not one of the awful companies who are busy fracking and starting up mothballed brown coal plants. Ahem). You can do the same. What that means is that for every unit of electricity you use, your retailer buys one unit from a renewable energy provider. The more you use, the more they buy, and overall, the more renewable energy gets generated. I have friends who really do say "I leave the lights on because buy green power, so the more we use the better". Which is not really correct if you're talking about overall environmental impact, because even "green power" takes resources to build and operate. If you do feel like putting money into building more green power, you're better off donating/investing in the companies directly or buying and keeping Renewable Energy Certificates (RECs - assuming you're in Australia).

The other thing you can do, even if you're renting (green renters), is work to reduce your electricity consumption. The lowest impact electricity is the electricity that doesn't get generated in the first place. LED or compact fluorescent light bulbs, when you replace your whitegoods buy for electricity consumption (and turn them off at the wall when not in use), if you have a PVR or computer that's on all the time, again, when replacing it buy for power consumption. If you're not downloading during the day, turn the modem etc off when you go out. Those things all add up, especially the parasitic loads (our washing machine is very low usage when it's washing, but draws 10W if it's turned on at the wall, even when it's "off" at that machine).

In terms of persuading other people to help, you're on the right track - ask people like sustainability.SE for tips, do some research, then focus on things that you know are likely to be effective. If you can persuade people you know to change their behaviour, great (and there are places online to get tips for that). Or join one of the many groups doing that on a larger scale, from local like the Marrickville Green Living Centre to national organisations of local groups like Clean Up Australia (there will be one in your area!) to straight up activist groups like GetUp or research-activist groups like Beyond Zero Emissions

  • Thanks for all that! Totally agree that the time of day strategy will have a significant impact only if thousands of people do it, hence the need to investigate it further. The other strategies you mentioned are probably even more effective but IMHO they're not so much better as complementary. Even with 100% green power one still creates demand on the fossil fuel sources as you write at the beginning and moving demand to less carbon-intensive periods will not reduce the amount of electricity bought from green generators.
    – eug
    Commented Jul 20, 2014 at 10:10
  • I dunno about complementary so much as shifting demand has a small impact, but for the same effort you could reduce demand by at least that much. Most people only have a finite amount of energy to put into things like this, so it's a question of where best to focus that energy (I've seen a lot of "good idea, just not very effective" efforts). But you're right that moving demand away from peak times reduces the use of peaking generators that are all fossil fuelled (in Australia at least).
    – Móż
    Commented Jul 20, 2014 at 23:37
  • I don't know about electricity in Australia, but in other countries I've lived, electricity demand during peak hours meant coal powered generators being turn on for compensation (and water from hydropower being pumped back uphill during the night). Some sustainable sources of energy (hydropower, windpower) prefer being used all-day evenly, so in a sense just using power during the day can make things worse from the sustainability point of view.
    – Earthliŋ
    Commented Jul 21, 2014 at 17:43
  • 1
    @Earthliŋ Australia's daily peak is 6-8pm at least during weekdays, and peaking plants are currently all fossil fuel. But we have large and increasing home PV generation so the OP's idea has some merit. But measuring demand is becoming harder because of the home PV's that often make only gross import and net usage values available to the network operator (ie, not including internal consumption).
    – Móż
    Commented Jul 21, 2014 at 23:19
  • Also, we are seeing more, longer periods of negative electricity prices due to coal plant inflexibility - the grid operator is actually charging generators for taking their electricity.
    – Móż
    Commented May 17, 2016 at 1:23

You're being quite specific with regard to solar... but in principle, it is possible to move your electricity consumption to minimise its carbon footprint.

Ecotricity (a UK "green" energy supplier) have a web page that shows the current carbon intensity of UK generation1, and gives a red/amber/green indication of whether you should turn stuff on now. If you can find something similar for wherever you live, that's a decent guide as to whether you should turn stuff on now, or wait for a higher proportion of renewables in your generation mix.

1 A number of other people have similar web pages - the raw data for the UK that I think they are calculated from is available at www.bmreports.com.

  • Wow, that's pretty neat although I can't find anything similar for Australia after a quick search.. The UK carbon content is "green" (relatively speaking, ahem) at night time, I suppose because wind & hydro are still running and the higher-carbon generators are not used so much off-peak? Australia also has wind and there's the famous Snowy Mountains hydro scheme near Sydney. Interestingly, another site (realtimecarbon.org) says that it's "experimental only...designed to stimulate debate"
    – eug
    Commented Jul 20, 2014 at 2:21
  • 2
    @eug wind, hydro, solar and nuclear. All of them have near-zero marginal cost (i.e. it costs the same to run them as not run them), so they tend to be used whenever they are available. From a quick search I haven't found anything similar for Aus - I guess it depends on the raw data being made available at sufficient temporal resolution. The best I could find for Aus was aemo.com.au/Electricity/Settlements/…, which only gives daily data.
    – Flyto
    Commented Jul 20, 2014 at 7:22
  • @SimonW good find. I looked but couldn't even find that. And Australia doesn't use nuclear so we can avoid questions about that. Although since we have uranium mines (in a world heritage area, no less!) we can't completely avoid the effects.
    – Móż
    Commented Jul 20, 2014 at 23:41
  • @eug, I would doubt the "greenness" at any given moment is determined by the renewal generation, but rather because some types of fossil fuel generation are greener than others. Presumably, generation used during peak loads is less efficient. Commented Jul 21, 2014 at 4:05
  • @eug not necessarily - I don't know how the system in Australia works, in in the UK the cheapest sources are used first. Often efficiency translates into cheapness, but not always.
    – Flyto
    Commented Jul 21, 2014 at 5:14

Currently, it's very beneficial but this will change in future.

Today, the most important new clean energy sources are wind power and solar power. Hydropower is usually available only in limited quantities, and only in some areas, although there are areas like Norway that have plenty of it.

Both solar and wind are weather dependent. If you are using electricity at times where solar and wind are unavailable or available in a very limited way, you are using fossil fuel produced electricity, most likely a natural gas fired power plant, although some areas may use oil fired power plants and China is still constructing coal power plants.

However, lithium ion batteries are becoming cheap very fast. This means it's more and more economical to charge a large lithium ion battery during daytime when the sun is shining and solar power is plentiful, and discharge it during the night. So very soon it's actually the case that you can use solar power even during the night!

However, lithium ion batteries don't solve the seasonality issue of solar power in high latitudes where there's practically none of it during the winter. Wind power is available during winter too but only when it's windy. If it's winter and it's calm, you can't charge the lithium ion batteries with solar power and the calm period may last so long, even over a week, that lithium ion batteries big enough to last during that period longer than week would be ridiculously expensive.

If you live in an area with near plentiful hydropower with storage pools, on calm winter days clean hydropower would provide the electricity needed.

However, in areas with practically no hydro storage pools like Germany, where there's still a real winter, the electricity would be produced by combined cycle gas turbine power plants during calm winter days.

Those gas turbines will likely eventually be modified to run on hydrogen. Hydrogen can be stored underground like natural gas, be transported in pipelines like natural gas, and be used in turbines designed or modified to work on hydrogen. Hydrogen can be created from water and electricity using electrolysis. Today the electrolysis cells are so expensive (and we still don't have enough wind and solar power to reduce price of electricity to zero during favorable weather) that clean hydrogen isn't cost-competitive with natural gas, but this is rapidly changing due to the falling prices of electrolysis cells, and also due to a certain maniac called Putin who has made natural gas ridiculously expensive in Europe.

So although today it's useful to consume electricity only when either wind or solar power is plentiful at the time of consuming electricity, it won't take long until the situation changes.

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