However, a separate analysis published in 2020 of data from 20,000 Ecobee smart thermostats in the US found that users sometimes overrode their device's schedule in a way that used less energy. So manual interventions, overall, were not as costly as expected. The study was part-funded by Ecobee.
Smart thermostats may struggle when users expect them to do all the work for them, suggests the lead author of the second study, Brent Huchuk, who now works for tech firm PassiveLogic. According to him, someone who is good at tweaking their own system is likely to do better than a smart thermostat.
"It's pretty hard to beat someone who's actively managing [their] heating and cooling schedule," he says.
"No shit, Sherlock?" as I have seen it put somewhere else!
2.0 kW/4.62 MWh pa in Ripples, 4.5 kWp W-facing pv, 9.5 kWh batt
30 solar thermal tubes, 2MWh pa in Stockport, plus Congleton and Kinlochbervie Hydros,
Most travel by bike, walking or bus/train. Veg, fruit - and Bees!
I can safely say that our recently fitted smart thermostat does save us money.
I couldn't figure out the scheduling on our old dumb one, so it operated at whatever my wife set it to, and I'd have to prod at the temperature to try to turn the temp down. The other issue was our living room zone would be set on a timer on the old system. Now we just have it on a very low temperature, using 30 minute boost when needed.
I can't get my head around why anyone would assume that "smart" anything will automatically save any money at all. If people want their homes heated to, say, 21°C, then it makes not a jot of difference to the cost if they use a smart thermostat, a dumb thermostat or no thermostat at all, the only way they are going to save money is to either reduce their heat losses or accept a lower room temperature.
Seems to be a daft obsession with connected devices being the best thing since sliced bread and the answer to all our woes, when the reality is that they increase overall global energy consumption, as all these smart devices both use power and increase the power used by all the servers that allow them to function.
25 off 250W Perlight solar panels, installed 2014, with a 6kW PowerOne inverter, about 6,000kWh/year generated
6 off Pylontech US3000C batteries, with a Sofar ME3000SP inverter
In that article the headline "My energy efficient home didn’t keep my family warm" is misleading because it's obvious from the content that it was definitely not an "energy efficient home", as insulation was missing and there was a lot of thermal bridging.
The headline should have been "building firm cheats and misleads customer", because that's what has really happened. The reality was that this woman's house was crap and badly built, as are very many new builds, as developers have been cheating and ignoring the regulations for decades (Grenfell Tower renovation is an example).
Successive governments have done sod all to actually stop developers lying, cheating and ignoring building regulations, if anything they have made it a great deal easier for them to do this, by privatising building control (so developers can just buy approval) and taking away all the independent checks on compliance with regs, or even checks that advertising claims for building products are accurate (most aren't in reality I found).
25 off 250W Perlight solar panels, installed 2014, with a 6kW PowerOne inverter, about 6,000kWh/year generated
6 off Pylontech US3000C batteries, with a Sofar ME3000SP inverter
I’m only operating the heating for 30 minutes in the morning, so the external temp sensor on the weather compensation is switched off, as I just want the heating on for 30 mins.
We have the Honeywell Evo Home wireless TRVs so effectively each rad is a zone. All set at 16degs so heating effectively off most of the time
Put a jumper on is my mantra!
Interestingly, manually adjusting a rad to 18degs sees it come on. Probably not the best use of an ASHP but we dont have underfloor yet so heating individual rooms as needed has to suffice for now
14Kw Mitsubishi Ecodan ASHP
22 x JA Solar 455W Mono Perc Half Cell Silvers
Solis 8.0Kw 5G Dual MPPT Inverter
13.5Kw Tesla Powerwall
Zappi 2 Charger
iBoost
I suspect that changing my heating controller from a simple thermostat and 24hr timeswitch to a programmable one has saved me a little money but it's more an improvement in convenience & comfort -I no longer have to manually override during the day at weekends or when I'm working from home. I can also now set a holiday mode so a) the house doesn't get too cold when I'm away and b) it can be back up to temperature just before my scheduled return.
I'd hope that a 'smart' thermostat would do some of the scheduling automatically.
My house (80's timber frame) has a fairly low 'thermal mass' so responds quite quickly to heating, a (more common) block built house isn't going to respond so well and will naturally keep a more constant temperature -no point in your house staying warm for a couple of hours after you've left for work.
Be interesting to know for sure whether a house with a long decrement delay construction is more or less costly to run than a house with a short decrement delay construction. My experience suggests that having a long decrement delay is better overall.
Our old house was a 1980's block and brick built one, that I upgraded a fair bit with decent double glazing, loads more loft insulation and cavity wall insulation. It had a very short decrement delay, just a couple of hours or so, and consequently would heat up very quickly in sunny weather and cool down very quickly in cold weather. It was generally not very comfortable, as there was always a wide variation in temperature from one room to another, in addition to the big swings in temperature with the weather. We'd keep the living room at a comfortable temperature, but the other rooms were always cooler, just to save energy. One thing I noticed was that this meant we kept the living room at a higher temperature that I think we needed, as the relative coolness of the little used rooms seemed to emphasise the need to keep the living room warm.
This house is is 100% timber construction, even the majority of the insulation is timber, in the form of cellulose. Consequently it has a long decrement delay, around 36 to 48 hours, so is very slow to heat up in hot weather and slow to cool down in cold weather. A neighbour, who spends a lot of time in the village church, likened the feel of our house in summer to the church, which is a massive Norman stone built affair. It also has very much lower heat losses than our old house, because of the much better airtightness, the heat recovery ventilation system, the absence of thermal bridging and the better insulation.
It's impossible to have much of a temperature differential from room to room, at best we manage to keep the unheated bedrooms maybe a degree or two cooler than the rooms on the ground floor. We find the house is comfortable with the ground floor rooms around a degree cooler than our old house, and I believe this is at least partly due to the more even temperature throughout the house. Means we don't bother to close doors downstairs, unless for other reasons, like reducing noise transmission from room to room.
It's also not practical to have zoned heating here, or to have the heating only on at times when we're in, as if we turn the heating off and let the house get cold it will take a day or two to get it back up to temperature. The heating costs are low, so this doesn't really matter. Running flat out, in the coldest weather we've had in the years we've lived here, the electricity for heating the house (at today's prices) costs around £1.13 per day. The average heating cost through winter is a lot lower than that, around £0.40 per day. If this winter heating season is similar to previous years our total heating bill for the year will be around £56, so very cheap, really. Being a pensioner I get the Winter Fuel Payment, and that is massively more than our entire annual heating bill, even with the big jump in prices this year. Hardly seems worth investing in expensive gadgets to try and reduce the heating bill, TBH.
25 off 250W Perlight solar panels, installed 2014, with a 6kW PowerOne inverter, about 6,000kWh/year generated
6 off Pylontech US3000C batteries, with a Sofar ME3000SP inverter
I think it's down to lifestyle. If you're at home all day then a long decrement delay costs you nothing (and keeps the place more comfortable with less temperature swing), if you're out at work all day then a cooler house is losing less heat.
Interesting that your 1980's block & brick house had a short decrement delay - guess that's down to poor insulation. Mine is timber frame so won't store much heat but also has 1980's insulation (apart from DG and more loft insulation) so loses it relatively quickly. I guess with passive house levels of insulation the heat loss is very slow regardless of the construction material.
Long decrement delay is definitely a bonus for summer heatwaves.
A few years back we had the cottage insulated with external wall insulation, the effects were dramatic to say the least and we also have a long thermal decay period even though the upstairs windows are always open all year around (gale force wind days we close them, but they are never closed for temperature) so we are nowhere close to being airtight. The walls are solid stone with a minimum thickness of 2.5 to 3ft, the loft is insulated to 750mm depth.
As you say we were approximately 2 to 3 weeks before we started feeling the heat in the house during the summer heat wave and overnight in winter we don't seem to lose much and at present its common to come downstairs and find the thermostat is still in the low 20's or high 19.x's
