Busting 2 myths about saving money when home charging in Hawaii

[Positvt]

Hi all,

Here are the 2 myths I have heard about saving money when home charging in Hawaii:
1. It is cheaper to charge your Tesla with the slow, standard mobile connector (110/120V @ 15A) than with a 50A (240V) socket using a NEMA 14-50 adapter or Tesla Wall Connector
2. It is cheaper to charge during peak (day time?) or non-peak (night time?) hours

I have done some research and here's what I have concluded - and would like confirmation on:

Hawaiian Electric charges are based purely on kilowatt-hours (kWh) of energy consumed – this is standard practice for all electric companies globally.

It does not matter at what rate you consume the unit of energy – which you can vary by the current (amps) or voltage (volts) – just how much energy you consume and that is measured in kilowatt-hours (kWh).

In some cities, the electric company charges more during “peak” hours and less during “off-peak” hours – called “time-based rate programs” – but Hawaii does not have this.

"Specific peak and off-peak hours vary by supplier, but a general rule of thumb is off-peak hours are at night, while peak hours occur during the day. Electricity used during the peak hours of the late afternoon will be more expensive than electricity used in the early morning."
Source: When Is Electricity the Cheapest? - Save On Energy Blog

Hawaiian Electric does have “tiered rates” in which the first 350 kWh/month is charged at a certain fixed rate (varies by month), e.g. $ 0.278481 per kWh.
The next 850 kWh/month is charged at a slightly higher rate, e.g. $ 0.290016 per kWh.
You can see this in the table down below which is for the month of Oct 2019.
Source: Time Based Rate Programs

Given the above, in short:
1. Always charge using your fastest charging option, e.g. 50-amp (240 volt) socket instead of standard mobile connector
2. Charge anytime – you won’t save any money by charging at different times of the day



I would very much appreciate if any of you can help to verify my conclusion and recommendations above.

Many thanks!

 

[Positvt]

Here are some references:

Hawaiian Electric | Understanding Your Bill
Understanding Your Bill

Hawaiian Electric | Effective Rate Summaries
Effective Rate Summaries list – Sep 2015 – Oct 2019 (*because the rates vary each month)
Effective Rate Summary
Oct 2019 Effective Rate Summary
https://www.hawaiianelectric.com/do.../rates/effective_rate_summary/efs_2019_10.pdf
Hawaiian Electric | Average Price of Electricity
Average Price of Electricity

 

[InParadise]

Hawaiian Electric has this program available for Time of Use (TOU) rates:
A Different Way to Save

 

[Positvt]

Hawaiian Electric has this program available for Time of Use (TOU) rates:
A Different Way to Save

Thanks, so I stand corrected - Hawaiian Electric does have a "time-based rate program" BUT it's not as simple as just having Peak and Off-Peak rates because while the Mid-Day (9am-5pm) rate is lower, outside of those times, the rate is higher. Thus, you might actually pay more under this program and have to enroll in it (max 5,000 people on Oahu for this pilot program).

 

[Positvt]

I note that as of 11/24/2019, 1,751 households have enrolled in the TOU program.
Can anyone who has signed up for it share their experience?...
Are you saving a lot?
Is it a challenge to try and shift most energy usage to between 9am and 5pm?
If your Tesla is parked at work from 9am-5pm then this probably makes little sense because you wouldn't be able to charge it at home at the lower rate.
I realize it really depends on the energy usage of each household but I would think that most have similar energy patterns (e.g. AC usage mostly in the day unless no one is home then?).

 

[nanimac]

Do you live in Hawaii?

 

[A Westpfal]

I note that as of 11/24/2019, 1,751 households have enrolled in the TOU program.
Can anyone who has signed up for it share their experience?...
Are you saving a lot?
Is it a challenge to try and shift most energy usage to between 9am and 5pm?
If your Tesla is parked at work from 9am-5pm then this probably makes little sense because you wouldn't be able to charge it at home at the lower rate.
I realize it really depends on the energy usage of each household but I would think that most have similar energy patterns (e.g. AC usage mostly in the day unless no one is home then?).

I have signed up for the Residential TOU metering in October. In a week they installed a new meter. It takes HECO 1-2 months for the rate plan to become active so I don't have actual cost yet. HECO has an paper form to complete but one of the helpful agents took care of this over the phone. They give you a one time trial period for 6 months and send you the TOU bill and how much you would have paid with the residential rate. If you don't like it you can switch back.

My work hours allow me to be able to charge my Model 3 Mid-range during the daytime (12.6cents/KwH is the current rate) so this is was my primary motivation.
I also have a timer on my water heater that turns on from 9-5. in cases of high demand I can override the timer so far this has not been a problem. I also schedule washer and dishwasher to start after 9am

This is a pilot program to encourage a shift in energy usage to daylight hours when there is a surplus of solar energy. This is the same rationale HECO use for the TOU rates for DC Fast Chargers installed on the island.

You could also install a large hot water tank with a tempering valve and use the tank as a thermal battery to charge during the daytime (like solar thermal systems do). You could also use A/C only during the daytime to and save on cooling bills

Aside from the hot water tank timer this is a no cost trial.

If you could get a low-cost Powerwall type system I imagine you could save money by running on battery power at night.
Anyone care to calculate the break even point?
Extending this absurdity maybe you could arbitrage power and sell it back at night. Too bad I can't tap my M3 62KwH battery as a power source vs a 14KwH Powerwall.

 

[Positvt]

Do you live in Hawaii?

No, I don't but I was born and raised in Hawaii (Moanalua High '85 and UH Manoa '90 grad) and all of my family is there.
I've been a Tesla Model S 70D owner in Hong Kong since 2015.
I'm doing this research for my father who recently got a Model 3 and lives in Hawaii Kai.
My sister and cousin who also live on Oahu will also be getting Model 3s.
My mom will likely get one next year too.
So while I do not live in Hawaii right now, I have very close ties.

 

[Positvt]

I have signed up for the Residential TOU metering in October. In a week they installed a new meter. It takes HECO 1-2 months for the rate plan to become active so I don't have actual cost yet. HECO has an paper form to complete but one of the helpful agents took care of this over the phone. They give you a one time trial period for 6 months and send you the TOU bill and how much you would have paid with the residential rate. If you don't like it you can switch back...

Thanks much for sharing your helpful and insightful experiences and thoughts - much appreciated. Great ideas too!

 

[ElectricKepi]

We have a photovoltaic system at our home, and just supplemented it with a Tesla PowerWall. Using solar to power our Tesla EV is a dream come true! Running out home and vehicle with free sunshine so abundant here is just awesome!

 

[gmtom1]

I will generally agree with most of @Positvt 1st post, except as noted, if you are on HECO's TOU residential rate plan, the incentive would be to schedule your Tesla to charge (either via scheduled start or finish by in the charging screen) within the 9-5 time period corresponding to the lowest rate. The method of charge (slow 110V vs. faster 240V) will not affect your cost, unless you exceed the 5pm end time.

Also, HECO used to have a program called TOU-EV-R (no longer available to new customers) which made the cheapest rates at night from 9pm-7am, and the peak highest rates from 5pm-9pm, and mid-rates from 7am-5pm during the week; there was no peak rate on the weekend. This is what I'm on, and if combined with PV, provided the best value since you'll be selling back energy to HECO at higher rates, while charging at the cheapest rate.

 

[A Westpfal]

I have signed up for the Residential TOU metering in October. In a week they installed a new meter. It takes HECO 1-2 months for the rate plan to become active so I don't have actual cost yet. HECO has an paper form to complete but one of the helpful agents took care of this over the phone. They give you a one time trial period for 6 months and send you the TOU bill and how much you would have paid with the residential rate. If you don't like it you can switch back.

My work hours allow me to be able to charge my Model 3 Mid-range during the daytime (12.6cents/KwH is the current rate) so this is was my primary motivation.
I also have a timer on my water heater that turns on from 9-5. in cases of high demand I can override the timer so far this has not been a problem. I also schedule washer and dishwasher to start after 9am

This is a pilot program to encourage a shift in energy usage to daylight hours when there is a surplus of solar energy. This is the same rationale HECO use for the TOU rates for DC Fast Chargers installed on the island.

You could also install a large hot water tank with a tempering valve and use the tank as a thermal battery to charge during the daytime (like solar thermal systems do). You could also use A/C only during the daytime to and save on cooling bills

Aside from the hot water tank timer this is a no cost trial.

If you could get a low-cost Powerwall type system I imagine you could save money by running on battery power at night.
Anyone care to calculate the break even point?
Extending this absurdity maybe you could arbitrage power and sell it back at night. Too bad I can't tap my M3 62KwH battery as a power source vs a 14KwH Powerwall.

I have completed my six month trial of the Interim Residential TOU rates. For the last six months I have saved between $50-$70 each month using around 1,200 KwH/month. This plan is definitely a keeper!

 

[Gu$ G]

Also, HECO used to have a program called TOU-EV-R (no longer available to new customers) which made the cheapest rates at night from 9pm-7am, and the peak highest rates from 5pm-9pm, and mid-rates from 7am-5pm during the week; there was no peak rate on the weekend. This is what I'm on, and if combined with PV, provided the best value since you'll be selling back energy to HECO at higher rates, while charging at the cheapest rate.

This is what I need! I'm in the market for a home, so if you ever decide to sell....!!

But we have had great success with the far less awesome TOU being offered now. We charge our two Tesla's between 9-5pm and save anywhere from $50-150 a month.