All Night Ultra-Low Electricity Rate and Charging Batteries.

This is also called Energy Arbitrage.

I recently converted my Hydro One electricity billing scheme to their new weekday Ultra Low rates, which are:

• 07:00 — 16:00 12.2 cents/kWh mid-peak
• 16:00 — 21:00 28.6 cents/kWh peak rates
• 21:00 — 23:00 12.2 cents/kWh mid-peak
• 23:00 — 07:00 2.8 cents/kWh Ultra Low rates

It is easy to see that one wants to use electricity after 11 p.m. through 7 a.m. and totally avoid the peak charge times of 4 p.m. through 9 p.m. Further, missing the mid-peak times would be a good idea as well.

Fortunately, I have a system that permits this with ease. I have 40 kWh of Tesla Powerwall home batteries sitting in my basement and batteries in two electric vehicles: a Mitsubishi and a Tesla. I have to handle each of these three batteries differently as the Tesla is on a Tesla Level 1 charger, and the Mitsubishi is on a more powerful FLO Level 2 charger, while the home Powerwall batteries are fully integrated into the Manotick Microgrid. The challenge then was to uniquely integrate these 3 batteries into the microgrid and the Hydro One grid to achieve the lowest cost to electrify and heat our home and routinely drive the two EVs. Fortunately, the last week has been terrible for solar energy due to heavy cloud cover and snow on the arrays. This means that the data presented is not confused with this solar energy source.

My cell phone app helps me keep track of what is happening, and I captured one screen to show what the actual energy picture turned out to be.

This is a 24-hour graph (midnight to midnight) of the actual use of grid-supplied energy. In addition to the three batteries, there is my 24-hour home base load (about 400 Watts demanded by refrigerators, instant on appliances, electric clocks, driveway lights, Christmas decorations, etc.), hot water heating and periodic peaks due to the running of the home ground source heat pump. It was necessary to set software configuration values in the FLO charger, the home batteries and the Tesla vehicle charging software. The above chart is a demonstration of actual performance. Starting at the left side, this automatic system record can be read as:

1. The blue line represents the base load, and the green line is the charging of the home batteries, which started one hour prior to the start of this graph (one hour on the prior day). There is a very significant total draw from the grid of about 12 kW at the ultra-low power rate.
2. The blue line drops out at about 2 a.m. as the home batteries are fully charged.
3. At 3 a.m. the Mitsubishi Level 2 charger kicks in for two hours as this EV battery gets charged. I had intentionally set the FLO charger to a low trickle charge rather than its full charging capacity to ease the charging stress on the Mitsubishi battery to maintain its range and lifetime.  After all, I have all night to do the charging.  There is no urgency.
4. There is about an hour when only the base load is drawing power before the Tesla EV charger kicks in at about 5 a.m. The Tesla vehicle software permits flexible charging such that the vehicle is charged to your desired level by a certain hour when you are heading off to work. The start time for this charging session is determined by the charge level at the start, the charging rate and the level of departure charge you desire. In my case, it is charged to 75% and completed at 7 a.m., just in time for power rates to increase from the ultra-low rate to the mid-peak rate.
5. From 7 a.m. until 11 p.m., there is very little grid interaction, and it is mainly due to the control system checking to see if the grid is still without a power outage. In reality, this is a tiny amount of power draw. The home batteries are supplying all the power requested to run the home electrical circuits and heat the house and hot water. These home batteries are slowly discharging all day.
6. Then we are at 11 p.m., where the home batteries need to be recharged after supplying power to the home (electricity and heating). The charging rate suddenly jumps to about 12 kW at the ultra-low-rate power.
7. The total draw from the grid for the day was 38.1 kWh at the low charge rate of $0.028/kWh for a total cost of $1.07.

When there is even a little bit of solar energy added into the mix, this total cost has been as low as 33 cents for each winter day. In the summer, this daily charge is typically zero to electrify the house, heat/cool the interior, and drive 2 EVs with the excess energy uploaded to the grid as credits that are used to offset the 38.1 kWh in the above winter day example.

The bottom line is that it costs $0.00 with the above example day as the saved credits from the summer have the honour of cancelling the amount shown on the winter monthly billing. In fact, for the entire year, the total money paid to Hydro One is the standard monthly connection fee, with zero for energy consumption. Hence, I say that I drive on sunshine, and my fuel source for the future is very economical as it uses the fusion reaction of the Sun and the core of the Earth.  No burning.   No GHG emissions.  Everything is electrified.

Further, this is a typical performance upgrade to the Manotick Microgrid that is made every year. In this case, there was zero investment money and no new hardware. Yes, it is a cost-avoidance upgrade without any change to the demand or supply of electrical energy.  However, every improvement is not investment free.