Archives 2024

How I reduced Electricity Demand Charges while charging two Tesla Electric Vehicles

Our electricity provider recently introduced a new Electricity Peak Demand Charge ($3.75/kW). This charge is based on the highest average 15-minutes of usage during our entire billing period.

We own two electric vehicles (EVs). We purchase all of our electricity from the electric company (e.g. we do NOT currently have solar panels). We have a home energy monitor (IotaWatt) that allows me to view our peak usage (kW) for the entire home with and without EV charging.

Here is a breakdown of our total 32kW peak usage ($120/mo peak demand fee):

  • Home: 12kW peak usage
  • Vehicle 1: 10kW peak usage (40A@240V)
  • Vehicle 2: 10kW peak usage (40A@240V)

Tesla Solutions

If you have 2+ Tesla Wall Connectors, use Group Power Management (GPM) to configure your wall connectors to limit their combined power consumption.

For our two vehicles, this setting reduces our peak demand from 32kW ($120/mo) to 22kW ($82.50/mo). This is a savings of $37.50/mo.

We were able to configure “Group Power Management” in our two Tesla Wall Connectors (3rd generation) to limit their combined usage to 40A@240V (10kW) rather than allowing each vehicle to charge at 40A. Up to 6 Tesla Wall Connectors can coordinate using DPM. Other chargers have similar features.

If you have 1 Tesla Wall Connector, use Dynamic Power Management (DPM) to configure your wall connector to throttle vehicle charging usage based on total home energy usage.

If we only had one Tesla Wall Connector, DPM could easily reduce our peak demand from 22kW ($82.50/mo) down to our household peak of 12kW ($45/mo). This would be a savings of $37.50/mo.

Tesla Wall Connector (3rd generation) supports “Dynamic Power Management“, which “adjusts charge rate in real-time based on the available power in your electrical panel”. DPM requires a specific home energy monitor (sold separately) be installed in your electric panel to monitor available power. This is a great solution to prevent EV charging from increasing your household peak demand. Unfortunately, DPM only supports a single Tesla Wall Connector at this time.

Open Source Solutions

If you have 2+ Tesla Wall Connectors (2nd generation), you can use open-source software to achieve Dynamic Power Management (DPM) across multiple wall connectors.

Several open-source projects are able to perform Dynamic Power Management with older Tesla Wall Connectors (2nd generation) but do not currently support the latest Tesla Wall Connector (3rd generation).

If you don’t mind a DIY solution and are familiar with Raspberry Pi and Linux, consider using one of these software projects to manage your total household usage to reduce your demand charge and/or to consume all available solar panel electricity generation. These projects can read your current home energy usage from several different home energy monitors and adjust wall connector power output in real-time to keep your total power consumption (kW) below a configured amount.

Custom Solution

If you have 2+ Tesla Wall Connectors, you can build custom API integrations to read home energy usage and adjust your Tesla vehicle charging rate.

This is my current solution until the open-source projects above support the latest Tesla Wall Connector (3rd generation). This reduces our peak demand from 32kW ($120/mo) down to our household peak of 12kW ($45/mo). This is a savings of $75/mo.

First, I setup an automation to automatically reduce my charging rate to a very low value (e.g. 5A) when each vehicle arrives at home and increase my charging rate to the max value (e.g. 40A) when each vehicle leaves home. Tessie can also perform this automation. This prevents each vehicle from causing a large peak before the following integration magic can begin.

My API integration reads real-time home energy usage from an IotaWatt home energy monitor API on my home network, then adjusts vehicle charging rates between 2A-40A using the vehicle API in the cloud.

Example: If I want to limit total home usage to 12kW and my home energy monitor reports total home usage (minus EV usage) is currently 2kW, the integration will make 10kW available to one vehicle or 5kW available to two vehicles.

The level of sophistication will depend on your imagination. Here are a few ideas:

  • Confirm how many vehicles are located at home and connected to Tesla Wall Connectors. Allocate the available power between each vehicle (e.g. 10kW available can be allocated to two vehicles evenly as 5kW per vehicle).
  • Calculate the % battery needing to be charged (e.g. desired SoC % – current SoC %) for each vehicle. Allocate the available power so the vehicle that needs larger total charge receives a larger % of the available power (e.g. 10kW available could be allocated as 2.5kW to Vehicle A needing to increase SoC from 60% to 80% plus 7.5kW to Vehicle B needing to increase SoC from 20% to 80%). This would help SoC % of Vehicle B recover more quickly.
  • Similar to prior example, but allocate available power to vehicle with lowest SoC %. When vehicle two vehicles have same lowest SoC %, allocate equal amount of available power to both. This helps ensure the vehicle with the lowest SoC % recovers as quickly as possible, but would require a buffer of 1-2% to prevent constantly starting/stopping charging on one vehicle if the vehicles have different capacity batteries.

NOTE: If you are managing a Tesla vehicle, consider using TeslaFi API or Tessie API since those platforms perform proper sleeping between requests. Otherwise, you will find that your battery state of charge decreases by several % per day when the car is idle because you keep waking up the computer.

Unfortunately, any of the following outages can cause your API integration to fail:

  • Home network outage
  • Home Internet outage
  • TeslaFi or Tessie API outage
  • Tesla API outage
  • Vehicle Internet outage

If any of the outages above happen during EV charging even ONCE during your billing cycle, this could result in a demand charge increase for the entire month. Here are several example scenarios:

  • Home is idle (e.g. <1kW). Vehicle is charging at full speed (e.g. 10kW or 40A). Large appliance (e.g. HVAC, hot water heater, etc) begins running during an outage. Vehicle charging is not reduced in real-time, resulting in undesired demand charge.
  • Home is idle (e.g. <1kW). Vehicle is charging at full speed (e.g. 10kW or 40A). Vehicle finishes charging. Because vehicle never left home, API integration has not reduced charging to very low value (e.g. 5A). Vehicle begins charging again while large appliances are running. Vehicle charging is not reduced in real-time due to outage, resulting in undesired demand charge. Workaround: Configure your API integration to reduce vehicle charging speed (e.g. 5A) when vehicle has finished charging.

Have you found another way to manage your peak energy demand charges? If so, please reply below. I would love to hear specifics!

EV Road Trip Tips and Stats from our First Tesla Road Trip (1800 miles; 17 Superchargers)

I am documenting my experience driving an Electric Vehicle on our first 1800 mile road trip from Missouri to Colorado in March 2024.

ABRP estimated 26h24m total drive time and 7h32m total charge time for our 1699 mile road trip. These stats are for the round-trip journey, not including any additional driving while at our destination. I intentionally used slightly conservative setting for “Reference consumption” in TeslaFi, which means their times should have been higher than our actual.

We recorded 31h11m actual drive time and 10h25m actual charge time (at Superchargers) for our 1813 mile road trip. The extra 114 miles of sight-seeing during our visit added about 2 hours drive time and about 30 minutes charge time.

Check back for a future analysis of estimated vs actual times for each drive segment and for each charge. It is not clear to me why our actual drive times were 7% longer than ABRP, but I suspect our charge times were longer than ABRP because we would stop for meals and charge longer than ABRP asked us to.

Meet our Electric Vehicle

We drove a 2016 Tesla Model X 90D with 130K miles that we purchased just two months prior to this road trip. Our 4 passengers sat in the first two rows of this 6 seat (3 row) configuration and we folded down the 3rd row.

Cargo Space was sufficient for 4 passengers. Our second row had an empty area between the seats where we stored a cooler and food/snack bags. Our front trunk stored items that require easy access, such as charging adapters, spare shoes, coats, gloves, hats. Our rear hidden/lower cargo area stored items specific to our destination, such as snow boots, toilet paper, paper towels, heavy clothing. Our rear cargo area was spacious after folding down the 3rd row seats and easily stored 3 full size luggage bags, 1 carry-on size bag, 4 backpacks, and several extra jackets and blankets. As driver, I still had 80%+ view through the rearview mirror.

Autopilot (AP1) features significantly reduced my driving fatigue during our 31 hour road trip! AP1 features include Adaptive Cruise Control and Lane Centering. These features use a forward-facing camera and a forward facing radar. These features performed very well.

Free Unlimited Supercharging (FUSC; SC01) allowed us to charge the battery for free at any Tesla Supercharger location.

Charging Thoughts

I wanted to be able to charge at our overnight stops to reduce time at Tesla Superchargers. Using several different charging adapters saved us 2h25m of charging time at Superchargers.

I wanted to be able to charge at any DCFC (DC Fast Charger) if a Tesla Supercharger was offline or full. We did not end up using either of our fast charging adapters.

  • All of the Superchargers locations were online when we arrived. I did have to move to a different Superchargers port one time on our trip due to a port not connecting properly.
  • All of the Supercharger locations had multiple available charging ports when we arrived. We only encountered Supercharger locations where >25% of the ports were in use when we were in the Kansas City and Denver metro areas.

Charging Adapters

I packed each of the following charging adapters. I also listed how often we used each adapter on this road trip.

  • Tesla J-1772 Charging Adapter
    • Used at hotel during return trip. Used 17 kWh ($6.66 paid).
  • Tesla Mobile Connector (Gen 2; Max 32A) w/ NEMA Adapter Bundle
    • Used 240V 30A adapter at friend’s home during outbound trip. Used 34 kWh ($5.10 worth).
    • Used 120V 15A adapter during our stay in CO. Used 54 kWh ($6.21 worth).
  • Tesla CSS Combo 1 Charging Adapter w/ Retrofit
    • NOT used during trip. We frequently use this when traveling non-Interstate in the midwest.
  • Tesla CHAdeMO Charging Adapter
    • NOT used during trip. We have not needed this adapter yet. Useful in rural areas if the CCS plug(s) are in use.

NOTE: I tested each adapter prior to our trip to make sure they worked with our road trip vehicle and to make sure I understood how to use each adapter. Nothing would be worse than using your last few % battery to drive to a charger, only to find out the adapter you have does not work!

EV Road Trip Preparation

Prior to this road trip, I drove our new (to us) EV on the following regional trips to get a feel for this vehicle’s power consumption. Efficiency improved as temperatures increased over the past few months, which was consistent with my prior driving experiences in our other EV.

  • 465 miles, 588 Wh/mile, 64% efficiency, 12°F (Springfield, MO to Kansas City, MO via Nevada MO)
  • 340 miles, 424 Wh/mile, 88% efficiency, 56°F (Springfield, MO to Kansas City, MO)
  • 570 miles, 387 Wh/mile, 96% efficiency, 64°F (Springfield, MO to Wichita, KS)

NOTE: Wh/mile shown above is from TeslaFi, which always reports a higher Wh/mile than the Tesla on-board computer. I have not determined why TeslaFi and Tesla on-board computer do not match.

I planned this road trip using ABRP (A Better Route Planner) to reduce my total charging time. The weather forecast was similar to the prior 340 mile trip above, so I adjusted the vehicle settings in ABRP and planned the prior 340 mile trip above in ABRP until the battery usage and charging times were similar to the actual TeslaFi battery and charging stats from the 340 mile trip above. Keep adjusting settings and planning new ABRP trips until your drive times and charging times match the actual stats from a similar prior actual trip. I used the Tesla navigation for my road trip. I manually added the extra ABRP charging stops to my trip in the Tesla navigation.

How can ABRP reduce charging time? If you use a DC Fast Charger (aka Tesla Supercharger) to charge your EV battery from 10% to 80%, you will quickly notice that the battery charges much faster for the first 10-20% and then charges more and more slowly as the SoC (State of Charge) approaches 100%. Tesla navigation tends suggest fewer but longer stops. ABRP can calculate when it makes more sense to stop twice and charge 10% to 50% each time instead of stopping once and charging 10% to 90%.

  • Example: It takes my EV about 20 minutes to add 40% SoC if I start with a low SoC (e.g. 15% to 55%). In comparison, it takes 1 hour 15 minutes to add 80% SoC (e.g. 15% to 95%). The second 40% (from 55% to 95%) takes 55 minutes! I save nearly 30 minutes by making two separate +40% charging stops, even if I allow 5 minutes to interrupt my trip for the second stop. ABRP handles the math for you.

Improving Efficiency Before Road Trip

I created this checklist to help ensure highest possible efficiency during our trip:

  • Tire Conditions need to be evaluated.
    • Are your tires road trip worthy?
      • Ask a tire shop to measure the remaining tread on your tires. Your tires should have no less than 4/32″ or 5/32″ of tread for a large roadtrip! For comparison, new tires have 10/32″ of tread. We were overdue for tires, so we purchased new tires with 10/32″ tread.
      • Ask a tire shop to check for excessive wear on the inside edge of your tires. Tesla vehicles are known for problems with inner tread wear due to improper wheel alignment. These issues cause flat tires and tire blow outs. You don’t need those problems on your road trip!
    • Do you have the proper tires for your road trip?
      • Mud and/or Snow Tires have the worst efficiency, but may be required if you plan to travel during winter, further north, or in mountains. You may also want/need studded tires for severe conditions and/or the low-profile removable snow chains sold by Tesla. Be aware your vehicle does not have enough clearance for most snow chains, even if you are able to raise your suspension height.
      • Highway Tires have the best efficiency, but may handle poorly in mud/snow and/or wet conditions. Most of the OEM tires (i.e. the same tires Tesla is known to put your vehicle when it was brand new) will likely fall into this category. Tire shops can tell you which tires are OEM tires. If you are trying to maximize efficiency, I keep hearing the “Hankook Ion EVO” tires have excellent efficiency and decent handling.
      • All Season Tires are a good compromise if there is a chance you will need to drive in mud/snow and/or wet conditions as long as you aren’t trying to drive through unplowed snow. We rode on a set of new Michelin Pilot Sport All Season 4.
  • Full Wheel Alignment performed prior to trip. I hire this out. I ask them to also look for any tire issues or suspension issues I need to be aware of before my trip since tire problems and suspension problems will reduce efficiency.
  • Adjust Tire Pressure to recommended cold tire pressure (see sticker inside driver door frame) after vehicle has been parked in shade or indoors for several hours. Avoid checking and adjusting pressure while your tires are WARM (e.g. right after driving and/or if tires are in sun) since the pressure will drop when they cool down.
  • Enable “Chill” mode to avoid excessive acceleration. Passing on a two lane at Mach 5 is awesome, but your efficiency takes a huge hit.
  • Configure Excessive Speed Chime to remind when exceeding speed limit. My personal preference is to chime when traveling 5+ mph over the speed limit. I want to be reminded of excessive speed since speeds over 55 mph have an exponential negative impact on efficiency.
  • Configure Regenerative Braking to Standard (or highest) available setting.
  • Automatically lower suspension to Low Mode when driving 60+ mph.
  • Enable “Range Mode” vehicle setting.
    • There are several different theories on exactly what this setting does. My understanding is that this setting 1) adjusts how the motors operate at highway speeds to improve efficiency at the expense of handling (e.g. do not use in snow/ice) and 2) reduces climate control output to improve efficiency (e.g. cabin temperature may not be comfortable in extremely cold or extremely hot weather).
  • Schedule Charge to desired % SoC such that charge finishes about an hour before road trip.
    • Example: My home charger adds about 10% SoC per hour. If I want to depart at 6AM with 100% SoC, I will charge vehicle to about 80% the night before and then I will schedule charge to 100% SoC around 3AM so that charge is complete around 5AM. Charging to 100% allows me to arrive in Kansas City with 15-20% SoC.
    • TIP: Adjust your departure SoC according to your first planned charging stop. Example: If the first charging stop on my road trip only used about 50% battery and I wanted to arrive with 20% remaining, I would want to depart with 70% SoC. I can plan ahead so that my vehicle SoC is around 50-60% the night before my roadtrip and then schedule charging to 70% the next morning such that charging finished an hour before departure.
  • Schedule Departure and enable “Precondition” so battery temperature is optimal before departure.

Improving Efficiency During Road Trip

I follow the practices below to increase my energy efficiency. EV road trips definitely require a much different and more patient mindset. My driving habits on road trips are much different than my daily driving habits, and I am rewarded with fewer and shorter charging stops as well as low risk of receiving a driving reward (and the associated travel interruption).

  1. Prefer seat warmers (or coolers) over very high heat (or very cold A/C). For example, I run seat warmer on lowest setting and keep cabin temperature around 69-70F when driving in 30-60F temperatures. All of our vehicle windows have thermal tint, but I still encourage passengers to wear layers in case they get too hot in the sun.
  2. Very gradual acceleration and deceleration.
  3. Manual acceleration and deceleration in areas with traffic control (e.g. stop lights, stop signs, roundabouts, etc). I leave a pretty decent distance between myself and the next person so that I can always take advantage of regenerative braking. My goal is to only use the actual brakes at speeds below 10mph (e.g. immediately before or at a stop sign/light). See practice #2.
  4. Adaptive Cruise Control in areas without traffic control, set to 2-3 car lengths and barely over the speed limit. This includes interstates and highways or urban roads that have very few stops.
  5. Follow Large Vehicles in areas without traffic control. When paired with practice #4 and choosing the right vehicle, I average a 10-15% efficiency gain.
    • How to choose your vehicle? The larger and more box-shaped, the better! My preference is semi trucks with enclosed trailers, moving trucks, RVs, then heavy duty pickup trucks.
      • l usually hop behind the first large vehicle I find, even if they are going 5mph UNDER speed limit and I patiently follow along until someone comes along who is going 0-5mph over speed limit.
      • I switch to a different vehicle if their speed varies too much. The heaviest vehicles will vary +/- 10mph during up/down hills, which aligns well with practice #2 if you have the patience for it. There are plenty of large vehicles that hold a steady speed +/- 2mph.
      • I’ll only follow heavy duty pickups as a last resort since they don’t follow practice #2.
      • I avoid tanker trucks and high-riding enclosed trailers (with large air gaps between trailer and wheels) because I only see 1/2 the efficiency gain with those veicles.
    • TIP: Increase your adaptive cruise distance if you are in heavy traffic to reduce your chances of being rear-ended if your large vehicle makes a sudden stop.
    • TIP: I avoid using the lowest adaptive cruise distance. I have experimented with different adaptive distances during long distance solo drives in multiple EVs and I am getting almost the same efficiency gains following at 2-3 car length setting as the 1 car length setting.
  6. Plan your arrival with time to spare. If I need to arrive at a certain time, I depart early so that I can arrive early. This allows me to enjoy the ride without feeling like I have to rush, which would have a negative impact on efficiency. If the trip goes smoothly, I can make extra leisure stops along the route as I get closer to my destination.

Overall Road Trip Experience

We definitely had to change our mindset when driving an EV on a long road trip. We were prepared to take our time and enjoy the journey. We use the charging stops as opportunities to take a break from driving, enjoy meal times (e.g. breakfast, lunch, or dinner), and if time allows we will walk around and explore the area.

The combination of the extra stops and the AP1 autopilot assist features made the drive a LOT less mentally draining for me, compared to our other 18-26 hour drives in the past few years. I am looking forward to our next road trip!

Driving Stats

Total Miles: 1813
Drive Count: 65
Drive Time: 31h11m
Average Speed: 58 mph
Average Consumption Rate: 488 Wh/mile

Charging Stats

Total Count: 30
Total Energy Used: 891.7 kWh
Total Energy Added: 764.3 kWh (86% efficiency)
Total Energy Cost: $7.24
Total Time: 79h29m

Fast Count: 17 (Tesla Superchargers)
Fast Energy Used: 779.6 kWh
Fast Energy Added: 694.2 kWh (89% efficiency)
Fast Cost: $0.00 (779.6kWh @ $0/kWh; FUSC SC01)
Fast Time: 10h25m (74.8 kW/h)

Cabin Count: 8 (useful for pre-conditioning)
Cabin Energy Used: 54.0 kWh
Cabin Energy Added: 25.3 kWh (47% efficiency)
Cabin Cost: $0.00 (54.0kW @ $0/kWh)
Cabin Time: 56h (1.0 kW/h)

Lodging Count: 4 (2 locations)
Lodging Energy Used: 52.0 kWh
Lodging Energy Added: 39.7 kWh (76% efficiency)
Lodging Cost: $6.66 (34.4kW @ $0/kWh; 17.6kW @ $0.38/kWh)
Lodging Time: 12h15m (4.2 kW/h)

Home Count: 1
Home Energy Used: 6.16 kWh
Home Energy Added: 5.51 kWh (89% efficiency)
Home Cost: $0.58 (6.16 kWh @ $0.105/kWh)
Home Time: 49m (5.0 kW/h)

Garmin Index Smart Scale WiFi “Incorrect Password” RESOLVED

My Garmin Index Smart Scale suddenly refused to connect to our home WiFi network.

Symptoms

  • Garmin Index Smart Scale attempting to upload weight history over the existing (previously configured and working) WiFi connection, then showing an “X” to indicate that the connection failed.
  • Garmin Connect App showing “Incorrect password” and “Enter the WPA2 password for this WIFI_NETWORK_NAME network” messages when attempting to reconfigure the WiFi network settings for the Garmin Index Smart Scale device.
  • Garmin Connect App showing “Network Not Found” message when attempting to reconfigure the WiFi network settings for the Garmin Index Smart Scale device.

Solution

I resolved this problem by changing my network DNS servers.

My network was configured to use the “Quad9 filtered DNSSEC” upstream DNS servers in my Pi-Hole configuration. I temporarily configured my home network to use different public DNS servers (Level 3) and the issue cleared up immediately. The next time I attempted to reconfigure the Smart Scale WiFi network in the Garmin App, it connected right away.

Troubleshooting

I noticed the scale connected via my phone hotspot immediately. I was using an iPhone with with iOS 17.2.1 at the time. Unsure if it matters, but I enabled the “Maximize Capability” setting in the Personal Hotspot settings (Settings > Cellular > Personal Hotspot).

Someone else mentioned the scale had to connect to Garmin services before the scale would verify the wifi connection, which made me suspicious of network filtering.

I disabled my Pi-Hole filtering, which did NOT resolve the issue. If it had, I could have looked at the query log to figure out what hostname lookups were being blocked and I could have added those hostname(s) to my filtering whitelist.

I temporarily changed my Pi-Hole upstream DNS servers. I had to try a few different servers before I finally found servers (Level 3) that worked. Garmin Index Smart Scale failed to connect while using these upstream public DNS servers:

  • Quad9 (filtered, DNSSEC)
  • Quad9 (unfiltered, no DNSSEC)