Peak pricing: Lessons learned so far

With 49 hours of peak pricing so far this winter (out of a maximum of 100), I've learned a few things. 

First, my basic consumption runs between 4 and 5 kW, as shown in the first two screen grabs from my account on Hydro's web page. The little bump every evening is likely hot water for the shower.

Second, I have been preheating the house prior to a peak event, possibly more than necessary. But the real cost is turning everything back up all at once, with peaks as high as 11 kW. This next screenshot illustrates an extreme example, where the average during the day was about 5.5 kW, but 8 kW in the evening. The 11 kW load right after the evening peak event was due to the house being quite cold, and I will probably not turn everything down so low in the future.

Third, the 2 kW impact of running an oven at 450F for 45 minutes at 18:00 is obvious in this next screenshot. 

Finally I have discovered that several of my thermostats and their associated baseboard heaters never really come into play, at least in the range of outside temperatures encountered so far this year. These are in rooms connected to my large open living area where the doors tend to be open. So rather than 10 thermostats, I really only need to worry about 5. These are the ductless heat pump; a convection unit in the living area; the heated floors in the kitchen and bathroom; and the study, which is in what was originally an unheated coal storage shed and which has two walls exposed to the outside. Leaving the others at 14C does not seem to impact the final temperature in those rooms; and furthermore I can simply shut the doors during a peak event and let the heat pump do it's job on re-opening. 

In other news I have been informed by a colleague of the existence of Hydro-Québec's Hilo program. This offers programmable thermostats that are controllable at a distance via an app on my smart phone. While not relying on Google or Amazon, I would be relying on Hydro's web services remaining functional. As well, it seems they do not yet have remote controllers for heat pumps or for convection units with built-in thermostats; and their system may not be able to control heated floors. So I may only be able to benefit for the single thermostat with baseboard, in the study area. I will dig and report. Stay tuned!

Stop the presses! Hydro-Québec starts thinking about peak pricing

Last fall, Hydro-Québec offered me the opportunity to participate in a pilot project to alter domestic power pricing depending on demand.  

Background

For readers outside Québec: Québecers rely to a very large degree on electricity for home heating and domestic hot water. Modern construction frequently has ducted, forced-air heating systems that can run on a range of energy sources; but my 100-year old row house is typical of older urban neighbourhoods or farmhouses, with no ductwork in the walls or floors: there are baseboard electric heaters in every room. In my case these replaced the pot-bellied coal stove installed when the place was built in about 1920; and I have supplemented it with a ductless heat pump that also serves as an air conditioner in summer.  

Peak power consumption in Quebec therefore arises in the middle of cold snaps in mid-winter, and demand can approach capacity when temperatures are very low. Building new hydro-electric capacity is expensive and increasingly challenging as all the best spots for dams already have dams. (I'm thinking of Site C in BC...) And demand can only increase as reliance on electric vehicles continues to grow. In spite of this, domestic rates have been fixed year round.

New rates for peak hours

The traditional domestic rate, known as Tariff D, is 6.08¢/kWh for the first 40 kWh per day (averaged over a typical billing period), and 9.38¢ for additional kilowatt-hours. In summer, my typical consumption, excluding air conditioning, is well below 40 kWh/d, so my daily demand charge is usually less than $2.43. (There is also a flat fee for connection to the network). 

The new Flex D tariff offers significantly reduced rates from December 1 to March 31, at 4.28¢ and 7.36¢ respectively. But the tradeoff is that Hydro may ask me, in an e-mail prior to 17:00, to cut consumption the following day from 06:00 to 09:00, from 16:00 to 20:00, or both; my demand charge during those periods becomes 50¢/kWh. (The total hours of reduced consumption will not exceed 100 hours, so this won't be more than 14 days, if both periods are requested, over the 4-month winter period.)

Specifics of my home

Having now been through 35 hours of reduced consumption, I can provide some comments. 

First, my 1100 square foot flat in an urban row house is on the ground floor, with an unheated crawl space below and two flats above. So heat loss through the ceiling is low, but the floors tend to be cool. As well, the presence of other row houses on both sides means there are not too many outside walls open to the elements compared to, say, a farmhouse or suburban bungalow. Finally when I renovated a few years ago, I took the opportunity to insulate outside walls (there was nothing but several layers of wood structure and outside brickwork in the past). Post-renovation, the place is a single large open area, with a couple of bedrooms and an office behind doors. Outside doors and windows are 25 years old and were state-of-the-art at the time; one door needs new seals but otherwise it all works well. So the heat losses should be reasonably low. The photo shows the indoor portion of the ductless heat pump on the wall high above a doorway, next to the kitchen cabinets and facing the large open area. 

Baseload

Being retired, and living alone, I have been able to push this as hard as possible. In the fall I established that the baseload in the absence of heating or cooling, which consists of refrigerator, laptop and screen, and lights (all LED since the renovations), is well under 1 kW. (The digital meter increases in 1 kWh increments, so it can take well over an hour for it to increment in this case.) This is illustrated below in an early attempt, where you can see the power use creeping up towards 20h00 as the place cooled down. (I didn't record the thermostat setpoints or temperatures on this occasion).

Maximum savings

By shutting all power to heat and hot water, and by eating prepared meals reheated in the microwave, I've established that I can drop my power level from about 5 kW to about 0.8 kW. Indoor temperature, keeping all doors closed, drops at about 1 degree C per hour. Essentially, starting at 21C, the temperature inside reaches 18C after 3 hours and 17C after 4 hours. This is with a temperature difference between inside and out of about 25C; with a difference of 35 degrees the rate of cooling is closer to 1.6C/h. Some rooms are cooler than others, and dropped faster; the small laundry room, with a large vent pipe connecting the dryer to outside, is a case in point. 

Realistic savings

This level of reduction, from 5 kW to 0.8 kW, is a bit extreme because the house is quite chilly at the end of it, and might not be acceptable to all family members. It also requires foregoing cooking using an electric range during the cold period. But it maximises potential savings which could be as high as $200 over the entire winter if Hydro-Québec wants the full 100 hours. A more realistic scenario is reducing to 1.1 kW, saving closer to $130 for the season, by maintaining some heating; I am also evaluating heating the house to 23C prior to reducing, which will increase my consumption in the cheaper period. I don't have data yet on this option but will evaluate and report the next time we get a really cold period.

Conclusions and recommendations

Overall some thoughts:

• This works if you are at home to adjust thermostats. In particular, as a retiree, getting up at 05:55 to shut everything down was a bit of a pain, to be frank. 
  
• Given the existence of individually controlled baseboard heaters in every room, I have a large number of thermostats (10, to be exact). So this involves running around setting each one; and given the relative thermal capacities and demands of each room, there is not a single setting that works for each. Being an engineer, I've worked up a spreadsheet for this...
  
• Some kind of programmable thermostat would be highly advisable for a family where people are in and out. In fact, being able to slave all the thermostats to a single input would be really nice.
• Using internet-connected thermostats would be helpful, but I recall reading recently that when Google went offline for a couple of hours, some folks with the Google Home app were unable to even turn on a light. How much control do you want to give to Google?
  
• Frequent opening of outside doors will throw all this out. I had workers coming through to install a new garage door, and while the garage is a separate building, I still had to go in and out to let them in, supervise and so on. The temperature decline hit 1.2C/h even though the day was relatively mild. 
• Hot water is potentially a hidden issue. If you take a shower at 05:45, then cut the heat at 06:00, the hot water tank may well be running for sometime after 06:00. Avoid large hot water uses at least an hour prior to the cut-off time, or kill power to it at the circuit breaker.
  
• Of course a dual-heat system, with the ability to switch from electricity to natural gas, will help out. It won't help greenhouse gas emissions if the power supply is all hydro-electric, as it is in Québec.
  
• As illustrated below, using the oven and a couple of stove-top elements for about 45 minutes to make dinner drove the power usage over that hour up to about 3 kW, for an average over the 4-hour period of about 1.35 kW. This turns out to be enough to just about eliminate any savings arising from the lower rate for the rest of the day; but there will continue to be savings from lower rates on other non-event days. 

The current cold snap being over, I'll have more data only once further cold events arise. 

In closing...

Like other provinces, Hydro-Québec will likely be putting some sort of pricing mechanism for residential customers in place at some time in the near future. Let's hope the pilot program teaches them something about the issues, and how to make it more consumer-friendly. At this point, it seems to me that the biggest issue for most people without a dual-heat system will be installing programmable and possibly remote controlled systems so you don't have to be home baby-sitting your system, even if the objective is merely to break even and avoid excessive use during high cost periods.

Stay tuned!