Originally Posted By: gathermewool
Originally Posted By: hattaresguy
The only benefit I see is for a vacation home so you can monitor the heating while your away.
HVAC systems are not designed for large temp swings, in modern houses your spending more energy to let it cool down a few degrees during the day and bring it back up than to just maintain it.
If your looking to reduce your bills add insulation, upgrade windows, and upgrade HVAC equipment.
Why wouldn't they be designed for large swings? My logic for keeping the heat way down at night and while we're at work during the day is two-fold:
1. The larger the delta-T between inside and out, the more heat loss, since heat transfer rises, regardless of insulation, with a higher delta-T. A leakier house with less insulation would see more benefit from letting the temperature droop lower during the day.
2. My old furnace takes time to heat up, as does all of the ducting. The heat coming out of the vents five minutes after the furnace has started is much warmer than at first start up. For this reason, I also have my thermostat hysteresis set at four degrees (i.e., if I set it at 60F, it will cycle between 58 and 62F)
Sure, I'm cold when I get home, but transitioning from 5F outside to 55-60F in the house makes it feel down right balmy, and only gets better when I click on the heat and warm up doubly.
The floors, walls, and every other solid object in the house still sucks up heat even after the thermostat clicks off, but that's what socks and warmer clothes are for. Besides, there are many nights where the thermostat will only need to click on one or two more times before we head to bed, and then it lowers back down to its cold setpoint, so it's not cycling over and over and over to warm up not only the air, but all of the furniture, too, because we don't spend enough time in the living room for it to do so.
At night, I run a little digital-thermostat-controlled ceramic heater, which keeps our room at a toasty 65-68F.
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As an experiment, we've locked our thermostat at 70F while the weather is so cold to determine how many more therms we burn. Our combined electric and gas bill is usually less than $200. With a kid due soon, it might be that we'll be leaving the heat higher throughout the day, so I'll be interested to see whether the bill shoots through the roof or has only a moderate increase....
My HVAC guys understand this better than me but you have to look at a couple of things.
1. How is your house heated, forced hot air responds quickly. Baseboard and if your even older radiators respond very slowly.
2. How old is your house and equipment. Typically I deal in new Energy Star construction so my stuff is very efficient. I turned the heat down in one of my condos I'm building yesterday morning from 66 to 55 and when I left at 3 it was still around 60...average outside temp yesterday was in the single digits. Older inefficient systems like radiators burn a lot of fuel getting all that iron up to temp, they are not designed for temp swings like that.
Everyone's equipment is different, but if you have a fairly modern house your really not going to gain a whole lot playing with the heat. You might save a few bucks if its a big house with lots of unused rooms, but you can do that without a Nest or Lyric, just hit the T stat down as you go out the door and up as you enter.
The last house I built we used Lyric's and again I was not impressed. I suspect if the owner kept the heat at say 68 for a month than played with it for another month the difference in the gas bill would be negligible. I simply view them as another item to fail, or to get hacked and have the heat turned off by an ex wife while your on vacation.
We also used Cree wifi enabled bulbs which are great, a garage door opener you can control with your phone which was also pretty good, and wifi door locks which IMHO also suck.
