reducing the co2 footprint is regarded as preferable to (and should be done prior to) increasing the footprint and adding an energy co-generation(solar panels i.e) to reduce the bills
consumed energy is a function of instant outputted power, effeciency of the used appliance and time the appliance was switched on. So first, one should buy appliances with high energy efficiency ratings, then automation can be used to reduce either the time of operation or intensity(power level, dimming etc) needed, or both.
In the guide i mentioned, there are a number of tactics described, like:
using roller shutters to keep just as much light as needed in a room, but reducing the need for aircon use
automatic dimming of lights to produce just as much light as needed
creating an “at home” and “away” and “on vacation” differentiation between workings of the automation system
when at home, presence detection in all main rooms, and decreasing of the delta of temperature between outside and heating/cooling set-point inside, when there is noone in a room
You will get the biggest impact on energy usage if you understand what is using most of the energy and focus on that first. It makes no sense to optimize your lights if your HVAC is consuming 80% of your total energy usage.
Beyond that what you can do will depend on the situation. There have already been several ideas mentioned here which boil down to these options:
only power a device when it’s needed
lower/raise the setting on the device so it consumes a little less energy
use other means to achieve the same goal (e.g. rollershades to avoid the heat rather than solely relying on the AC, improving the insulation, etc.)
replace the device with one that consumes less power (note, replacing a perfectly fine and working device with a new one may have negative ecological impacts that overwhelm the impact of the energy savings, new is not always better all things considered).
In my experience, the third option usually has the biggest impact over all compared to the others. But at that point you are outside the realm of automation and into the realm of good building practices and renovation.
In the realm of automation, good presence detection is going to be key. If you have fine control over your house on a room by room basis (e.g. each room has it’s own climate control, lighting, etc) then the more fine grained the presence detection the better (i.e. down to which room is occupied). Though I suspect this leads to diminishing returns for the amount of effort expended.
I started with moving a smart metering around all that always-on / most used devices to get a comfortable long term measurement of energy consumption.
And then replaced devices with high consumpions like old network switches or monitors.
It is a bit of an issue to replace functional devices, but if the energy cut is high enough it should be worth it in the long term.
And some of the older always-on (or standby) devices where really of the roof.
The monitor e.g. I sold to someone not using it 40h a week where the high consumption rate had lesser impact.
And as mentioned a total consumption overview does help a lot to prioritize actions.
So you can focus effort where it matters.
I am still missing 33% of our consumption. Most of it should be cooking/baking which I am not able to measure yet.
Last was replacing the old sat-tv-switch to a passive one. Should reduce about 3% of our annual consumption. So the small things can start to matter if you addressed all the big issues.
You have to do some maths, if a new device could help you to save money.
In my case i got a 25 year old freezer for free from a coworker when we moved into our new house. I installed a sonoff pow for measuring the power consumption for 2 years now and i can say, if i would buy a new freezer with the best power consumption class (in germany A+++), i can save money in about 15-20 years…
So it would be a very bad idea to remove this old “power hungry” freezer as long as it is running without problems.