[oliyoung]

As an Australian, the lack of anxiety and guilt you get when you're using 10-12 hours of air conditioning in the middle of summer and not paying for a cent of it because your solar panels are covering is worth more than anything

[dhotson]

Yeah totally, nice to be able to put the AC/heater on "for free". I even got a negative power bill once!

In my specific case, I barely use much power so home solar covers basically all of the usage, my bill is dominated by the daily charge, so the usage component is practically irrelevant to me.

[AtlasBarfed]

Why shouldn't that be true practically every consumer home in the world?

Yes, grid scale deployments are cheaper, but I'm generally guessing a lot of the grid scale solar deployments do not price in the grid infrastructure adaptation costs, and I'm not even talking about grid storage.

Consumer rooftop solar is fundamentally democratic: it reduces reliance on centralized institutions for power delivery, Make society a lot more resilient in bad weather and other emergency situations, insulates everyday people from wild variations and petroleum and other consumable energy availability.

Combined with plug-in hybrid electric vehicles, it would enable electrification of 80 and 90% of daily driving without grid infrastructure costs.

[brabel]

> Why shouldn't that be true practically every consumer home in the world?

Here in Sweden nearly all of the electricity bill you pay is concentrated on the winter months when there is literally zero sunshine. Even then solar is popular here. I calculated that installing solar would take around 10 years or more to pay for itself, but I have very little hope to stay in the same house all that time so for me it seemed like a bad investment.

That said, if you live in places where it’s sunny most of the time even in winter, like Australia, then solar is absolutely great, just don’t assume most places are like that.

[ghiculescu]

10 year ROI is what I got quoted on a solar setup. I live in Queensland. It’s very sunny here.

[brabel]

Wow your current electricity must be really expensive... or your solar setup is?? Also the calculation was done by the company selling it, I'm pretty sure that was far too optimistic.

[jazoom]

That actually sounds pessimistic to me. My ROI for 18kW solar plus 42kWh battery will be under 3 years.

- Expensive electricity

- Government subsidy for solar and battery

- Much sunshine

- 3 hours free charging daily

Nearly $5000 yearly bill gone. $14000 installation cost post rebate.

[brabel]

With a calculation like that I'd buy solar in a heart beat!

But as I said, my main concern is my winter bill, which I know by asking people who own solar in the region, is almost the same with solar since there's no sun at all (it's not that it's cloudy, it's that the entire day duration is like 4 hours - under which you barely feel any sun heat and in practice the solar output is exactly zero on the worst month and near zero for 4 or so months). Hence the very long ROI here, but I agree that for Queensland, 10 years would be a bit too long if you dimension the solar array properly.

[AtlasBarfed]

You are mere hundreds of miles from cheap Chinese panel manufacturing. The Chinese are going to pump manufacturing oversupply for likely a decade more.

10 years roi is mass scale corruption

[grey-area]

You should still feel some guilt for the heat pollution your air conditioning causes for those outside your house, esp. in an urban area.

[lnsru]

Can you please elaborate more on pollution from air conditioning equipment and heat pumps. I was thinking they are closed systems.

[grey-area]

Sorry autocorrect changed heat pollution to ‘what pollution’, I’ve fixed that now.

There is some impact on others, particularly those without ac.

[CalRobert]

If you’re using rooftop solar then presumably the net heat generated by your aircon is the same as the amount your roof is no longer absorbing. Otherwise you just described a perpetual motion machine?

[grey-area]

I imagine that absorption by the roof or panels is around the same - however the aircon moves heat from inside to outside, so you are moving heat outside for other people to deal with. In an isolated house it makes little difference. If every building has aircon in a city it does impact outside temperatures and adds to the heat island effect.

[CalRobert]

Right, but energy that would have heated the roof goes towards powering the aircon (which likely is on the roof itself), which then emits the same amount of heat, no?

Say a roof is absorbing 10000 watts. You install solar panels that absorb 2000 watts, used to power an airco. You now have your roof absorbing 8000 watts (released as heat) and ann airco absorbing (using) 2000 watts (also released as heat). Am I wrong? Seems like a conservation of energy problem. And you get a cooler roof so less airco demand too!

[brabel]

In a country like Australia where building density is extremely low that’s a negligible problem?!

[grey-area]

Sure if building density is low in your area and you have no nearby neighbours it probably doesn’t matter, you’d just be heating your surroundings a little.

[yurishimo]

Or, we could lobby politicians to actually improve the lives of their constituents by making climate control appliances so affordable and ubiquitous that it's no longer an issue and we can stop accidental deaths attributed to heat. More green spaces can also help mitigate the impact.

The reality is that a lot of old western europe was built for a climate that no longer exists. Houses are built to prioritize holding on to heat and rebuilding entire cities is definitely not possible if we're already bickering so much about adding heat pumps.

Yes, heat pumps may create a rise in temperatures in cities, but there are other things we can do as a society to also lower temperatures as to create a net-neutral impact.

[grey-area]

Schemes like the Paris central cooling one are interesting here - there are other possible solutions in cities too.

And sure yes combined with other measures AC can be a net good.

[CalRobert]

This is heat that would have escaped the house anyway

[grey-area]

No, air conditioning units generate heat (that is how they cool!) and do contribute to local warming. Without AC the house reaches equilibrium with outside. With AC the house is cooled and that heat has to go somewhere.

[scheeseman486]

They don't generate heat in the sense that heat is generated from nothing. If the AC is being powered by solar, then the energy that is powering the heat pump has already hit the earth and has become part of that system. The energy that would otherwise have hit the roofing and been radiated is more focused around the radiators, but as soon as that dissipates into the air the difference to the local climate isn't any different.

If the roof was white and reflective then a lot more of that light would be reflected, but most roofing isn't.

Your logic isn't really compatible with the laws of thermodynamics.

[grey-area]

Solar energy is not just infrared, and infrared is not what is used by PV solar. So not it’s not equivalent and anyway doesn’t in any way impact the extra heating effect of a new heat source on the ground.

Instead of generate heat you could say they move heat if you like, from inside to outside.

[scheeseman486]

All absorbed light gets turned into heat, infrared or otherwise (I'm not sure why you brought up IR?); solar panels catch some of that spectrum. I'm not sure what argument you're trying to make here, particularly given the second paragraph seems to contradict the first; "extra heating effect" (from where does this "extra" come from?) vs "you could say they move heat if you like" which yeah, not really about what I like, that's just how physics works, can't get any more fundamental than the law of conservation of energy.

You said that AC/heat pumps "generate" heat and if they were powered by fossil fuels, in an roundabout way they do. But if they're driven by solar, there's no long-trapped energy being expelled and therefore no "extra" energy added to the system beyond what the sun is providing.

[CalRobert]

Right, but assuming conservation of energy holds then the net should stay the same, right? Unless solar panels have lower albedo than the roof they’re sitting on (considering how many roofs are flat black tar that seems unlikely…)

[oliyoung]

that's inconsequential to keeping my family cool on the third 43c degree day in a week