I am a little bit unenthusiastic about Nest integration into the Mercedes Benz where it tells Nest to warm up the house prior to arrival. What a waste of energy! Is it so difficult for physical human body to endure some discomfort while the house warms up? Imagine thousands of household doing something similar.
OK, there could be a use-case where the elderly is due to arrive home and needs the house to be at the right temperature for health reasons. But this is clearly not the use case being put forward by Nest. It uses s luxury Mercedes Benz and is spinning it for luxury market.
Wasting/saving energy is not as simple a calculation as that. When energy is at peak use (say in the winter, around 5:30/6:00 when everybody returns from work), it becomes more expensive for energy companies to procure the requisite energy needed. During these peak times, they often have to buy energy from other companies at a higher cost or find less efficient means of generating it (e.g. coal) to meet the demand. Getting an accurate picture of estimated energy demand can actually save a lot of money/energy for customers.
I work at Nest and it may be a little unclear at the moment (we're working on it), but The Nest API does not guarantee that if you send an ETA of 15 minutes (docs: https://developer.nest.com/documentation/eta-guide), the home will heat to the appropriate level in 15 minutes. It's actually filtered through our algorithms to determine the best course of action to not waste energy but also provide the appropriate level of comfort.
I looked into the nest but I don't think it would save me any energy. And I'm wondering if that's actually true for lots of people.
I have a modulating (i.e. change flame level) condensing boiler (the highest efficiency available). I programmed it to run as close to 24/7 as I could, because that way it uses the lowest flame, which is the most efficient flame.
When I tried a setback thermostat when the boiler attempted to rewarm the house it shifted to a higher and therefor less efficient flame. So I gave up on that and let it run on low all the time. So there would be no peak usage by me.
As people shift to more efficient ways to heating I suspect that this will happen to everyone. Not just modulating boilers, but also multi-stage heating with a heat pump. By trying to rapidly heat the home you can't use the heat pump.
It's also true with an A/C - the faster you are trying to cool the larger temperature gradient you need, and therefor you lose efficiency.
It's also true with an A/C - the faster you are trying to cool the larger temperature gradient you need, and therefor you lose efficiency.
I'm not sure that's always correct. The Coefficient of Performance (heat moved/work done, higher COP is better) of an A/C is:
COP = T_hot / (T_hot - T_cold).
T_cold is the inside temp, T_hot is outside of the heat exchanger. The narrow the temperature range, the better the COP. Thus the A/C will actually be more efficient in terms of heat moved per watt while it's cooling a warm house down than when it's already cool.
There's one other factor that applies. The rate of heat transferring into the house is proportional to the temperature difference. Once the house has warmed up, you reach equilibrium. The net heat flow stops, so the total amount of energy you need to remove later stops rising. If you run the A/C all the time, heat is transferring in all the time. So the total amount of heat you need to move back outside in a day increases significantly if you leave the A/C on.
> I programmed it to run as close to 24/7 as I could, because that way it uses the lowest flame, which is the most efficient flame.
The energy loss from your home increases as the differential between inside and outside increases, right? So at night or when you're out, if your house were kept colder, then you'd lose less energy to the outside.
So by keeping your heating running 24/7, you're wasting some energy in the extra energy loss when you're out, right?
How does this compare to the efficiency gain by running your more efficient flame? Have you calculated or measured that you actually save energy overall?
> I work at Nest and it may be a little unclear at the moment (we're working on it), but The Nest API does not guarantee that if you send an ETA of 15 minutes (docs: https://developer.nest.com/documentation/eta-guide), the home will heat to the appropriate level in 15 minutes. It's actually filtered through our algorithms to determine the best course of action to not waste energy but also provide the appropriate level of comfort.
So you're accepting the ETA request not as a demand to obtain a certain temperature, but as a request, and then still taking utility demand information into account. Excellent.
I am not talking about wasting money, I am talking about the actual energy itself as money is more renewable than energy. Once it has been used, it is extremely difficult to get back.
Firstly, the premise of that scenario, is the house is cold while the person is gone. That means SAVING on energy costs by not heating the house unnecessarily while no one is inside, which is the current de facto standard. (Do you turn off the heat when you go to work? I certainly don't)
Secondly, it's silly to object to innovation that allows humanity to be frivolous or wasteful according to their desires. Where do you draw the line? Why have central heating in the first place? Is it that difficult to wear a sweater indoors? If people want to be warm, they will utilize technology to be warm. And if that technology progresses to allow this process to be simple, efficient, and automated, people will use it. And not just those in the luxury market.
Yes I have the heating on a timer and its off when I am at work. I turn it on if its cold and I working from home or its the weekend. I believe this is normal...
Any HVAC system installed or revamped in the past 15 years is likely to have a programmable thermostat. Whether people are using these _correctly_ or not (which as others have touched on here is not necessarily super intuitive, part of the problem Nest is meant to solve), I think attempts of some sort at saving energy with these is pretty common.
Many years ago I instrumented my house using a wireless network of 20 motes we had spare from a research project. One of my conclusions was that the house warmed up and cooled down quite a bit slower than I had assumed. Our heating at the time was on a timed thermostat. I ended up moving the "on" times 30 minutes earlier and the "off" times an hour earlier. We saved energy and had a more pleasant environment.
This was using dumb thermostat technology. If we were back later than usual, the house still got warm. If we stayed up later than normal, the house started to get chilly. Smart thermostats that know what you're doing can help even more, but the less predictable you are, the more the gains from the thermostat being linked to other systems to monitor what you're doing. If you're home the same time every day and go to bed at the same time, the gains will be less.
BTW, I also discovered that our dishwasher warmed the kitchen by 2C. The obvious conclusion was that it was best to use its timer to start it at 4am, so the waste heat has already warmed the kitchen by the time we're up for breakfast.
Millions of thousands of homes today simply leave their thermostat at the same temperature all the time, failing to optimize for the large portions of the day when nobody is home because it's simpler (and they probably don't have a timed thermostat, or they can't figure out how to set it up.)
Imagine thousands of households doing something smarter.
Not sure this is so common in the uk. My heating is almost always off, and if it gets cold we have a timer and a thermostat, so it comes on for an hour in the morning and a couple of hours in the evening.
I have noticed a trend among our friends, (not technical folks), who actually turns off their heating when they go out. It is as common as turning off their lights when they leave the room.
I guess Nest is heading towards this direction, but pre-warming a house very "first-world".
Not to keep harping on the subject (see my comments above), but pre-warming or pre-cooling houses is actually a really great solution to solving our energy problems with algorithms. It's not strictly a "first world" problem.
Imagine a neighborhood of 100 homes where you know all 100 people will return approximately at 6pm in the winter, and they all want 72 degrees. Taking into account the insulation of each home, if you could pre-heat the homes on a rolling schedule (say, heat 25 of them to 75 degrees at 3pm, accounting for 1 degree of heat dissipation per hour, heat another 25 to 74 degrees at 4pm, etc.), you will actually in aggregate save a lot of energy and cost because of inefficiencies in the way we deliver and generate energy during peak times.
That is an interest way of distributing loading of the peak heating requirements. Does Nest have a ability to interact with the other Nest in the neighborhood? Or is it all controlled from a central server?
Not (yet) with other Nests that I'm aware of, but they're making deals with the power companies. Users can get discounts on their bill for allowing the power company to bump energy use down a degree or two during peak times.
Owning a house with central heating / AC that can be controlled by a Nest Thermostat via your household wifi from your smartphone while driving home in your Mercedes is a pretty "first-world" thing.
Especially given that this works best for second homes like a weekend house in Tahoe where it might take a full day to warm up if you left the heat off all week.
When your house is not insulated properly and you live in a cold climate, it's actually better to not turn the heat off completely. It takes more energy to warm a stone cold house than to keep it at approx. 62 degrees.
A simple, programmable thermostat will make up for the purchase within the first year of service.
This is not true. It might seem that way because of how long it takes your house to warm up. There is no momentum or stiction with heat transfer. When the inside of your house is warmer than the outside you are losing some amount of heat to the outside proportional to the difference. Any heat you add to maintain that difference when you are not home is wasted. As long as you can tolerate a stone cold house when you return, your best efficiency is to just turn the heat off. This is assuming you have an on-off heating system, someone mentioned a throttling system is more efficient at a low flame rate so that made it better to leave the heat on low all the time. I am skeptical of that claim but don't have enough information
It seems intuitive that heat exchanger eff increases with decreased flow rate. Also air handling is always best done as slowly as possible, because you're trying to move air, not make noise and turbulence. There doesn't seem to be any intuitive reason to think eff would be higher at low rates unless its doing something insane like varying fuel/air ratios to get a desired heat flow or some kind of slow PWM with repeated ignition losses. Real furnaces don't work like that, so...
My otherwise boring furnace is variable speed and the longer its on, the faster it runs. It's really roaring after about 30 minutes. Its more than a decade old, this is pretty old COTS tech. My first zillion BTU cost me somewhat less than my last zillion BTU in any heating cycle.
I live in a cold northern climate with great insulation and low heating bills and a variable speed furnace and the house is basically never empty (spouse and I work at home often enough, etc). The whole "nest" idea doesn't work financially for me although it is interesting to watch.
That was me, with the throttling system. It's called modulation, and is very common in Europe.
While there is no momentum in heat transfer, the walls of your house store heat. If you're away long enough to allow your house to cool down it will take more fuel than it would to keep it at a reasonable temperature. Also, this is much, much more comfortable than to arrive in a stone cold house, only to open a window 30 minutes later because of the blazing heat.
I'm not saying it's always better to keep a certain temperature, though. It depends on the time that you're away, the insulation of your house, the outside temperature, the efficiency of your boiler, etcetera. But, having lived in houses with ordinary thermostats and non-modulating boilers and houses with programmable thermostats and modulating boilers I can tell you this: I'm not going back to the old stuff. The indoor climate is so much better now!
We have a thermostat in our house that has a weekly programme: it turns the heat on in the morning, then off at 7:30 when everyone is at work/school, back on at 16:30 so that the house is heated when we get back home from work/school, and off again at 22:30 around bedtime. During weekends it heats during the day and is off during the night.
There was never any question on using this system; everyone I know has this, unless they live in a really old house or an apartment block with common heating. It's a standard for heating systems called OpenTherm.
Is this really that uncommon, or is this a European thing?
We have similar in the UK.
I bought the Nest thermostat originally but could not see how to make it work for me.
I like the shineyness and am a big home automation fan (I have mostly LightwaveRF 433mhz sockets and switches and some hand rolled code connected to google calendars https://github.com/pauly/lightwaverf) but am going to wait a while before buying into this.
I'm in the same boat as you (Western US here). I've had a programmable digital thermostat for at least 10 years, and many newer apartments have them already installed.
I can't believe more people don't know about these things. They predate the Nest by 5-10 years.
People tend to waste energy when they're cold - it's the false savings of turning off the air-conditioner.
You think you can bear it - until you absolutely can't, and immediately turn it to the highest setting you can because damn it you want it warm now.
Then it's warm (or too hot) and you turn it off to cool down faster and...rinse repeat.
For most people it's far more efficient to turn the air conditioner on to a given temperature setting, so when they enter a room they don't have any immediate reaction to "make it warmer or colder". We are exceptionally bad at judging these things in the moment.
For summer, we're lucky enough to live an a near-coastal region where 90 degree days are usually followed by 60-degree nights with decent evening winds - we used the AC 3-4 times this summer instead of the whole house fan (to avoid pulling in neighbor's BBQ smoke), but for the rest the fan is adequate.
In Winter, we use space heaters (new ceramic ones that start outputting heat in 10 seconds that are kid safe to touch) in the bedrooms and a very low central heat.
Of course we have over-standard insulation and trees nearby - anyone in a top floor of an apartment complex will most certainly be using AC almost every summer day (but probably not shivering at all during winters).
> Is it so difficult for physical human body to endure some discomfort while the house warms up?
A person driving a Mercedes-Benz is probably not one to care about saving the half a dollar in energy consumption to pre-heat the living space. So, it's not difficult, but not not-difficult, either.
OK, there could be a use-case where the elderly is due to arrive home and needs the house to be at the right temperature for health reasons. But this is clearly not the use case being put forward by Nest. It uses s luxury Mercedes Benz and is spinning it for luxury market.