Tou calculation help.

[electronchaser]

EVs in the household have grown, was considering if TOU rates make sense. My utility gives me a 16 hour window to charge with 32 amps, so its more than enough time to top off evs in rotation.

I use about 1300-1500 kWh per month.

main draws A/C and EV charging.

I do about 250- 350kWh worth of EV battery recharges weekly.


bottom line: tou worth it?

here's how my utility breaks down rates:

Customer Charge - per meter per day $0.4400

Energy Charges - per kWh

July through October (High Season)
First 10kWh per day $0.1620
Next 10kWh per day $0.2008
Remaining kWh $0.2398

November through June (Low Season)
First 10kWh per day $0.1358
Next 10kWh per day $0.1682
Remaining kWh $0.2075

VS

TOU rates:

Customer Charge - per meter per day $0.8200

Energy Charges - perkWh

July through October (High Season)
Base Period * $0.1391
Peak Period ** $0.2781

November through June (Low Season)
Base Period * $0.1159
Peak Period *** $0.2318

weekends and holidays are also charged at base rate.

anything else I forgot to consider?
thanks!

 

[eNate]

It seems to me that you've got it mostly figured out. You need to present what the daily electricity consumption looks like. Does your utility provide you a hourly breakdown so that you can form an idea of what you're using and at what time? Do you charge your car daily and can you keep it under the 10 kWh daily threshold?

I would work it backwards, calculating what the car costs for each plan and backing it out.

If you stick with the tiered pricing plan you also have to consider that you'll have to monitor household and car usage closely every time you plug it, because it's really easy to cross the 10 kWh daily thresholds. My gut call is that at your average of 50kWh per day total usage, and 40kWh of that being for the EVs, if you can limit charging the cars to off-peak periods, the TOU pricing is a no brainer.

 

[JohnWasser]

"I use about 1300-1500 kWh per month."
So roughly 47/day

"I do about 250- 350kWh worth of EV battery recharges weekly."
So roughly 43/day.

Non-TOD:
High Season: 0.44 + 10*0.1620 + 10*0.2008 + 27*0.2398
= 0.44 + 1.620 + 2.008 + 6.4746
= $10.5426/day

Low Season: 0.44 + 10*0.1358 + 10*0.1682 + 27*0.2075
= 0.44 + 1.358 + 1.682 + 5.6025
= $9.0825/day

TOD:
High Season: 0.82 + 43 * 0.1391 + 4 * 0.2781 = 0.82 + 5.9813 + 1.1124 = $7.9137/day
Low Season: 0.82 + 43 * 0.1159 + 4 * 0.2318 = 0.82 + 4.9837 + 0.9272 = $6.7309/day

Looks like you save about $2/day with TOD charging when you do your 43kWh of car charging during off-peak hours.

 

[eNate]

That assumes though that charging is done consistently every day, versus every few days as needed. Or that a Monday household usage looks the same as a Saturday.

My usage is much more spikey so higher tiers tended to hit me on certain days but not most days.

 

[JohnWasser]

My usage is much more spikey so higher tiers tended to hit me on certain days but not most days.

So a much larger portion of your charging was at the higher tier rate. That means your savings by switching to TOU would be even greater.

 

[eNate]

My usage is much more spikey so higher tiers tended to hit me on certain days but not most days.

So a much larger portion of your charging was at the higher tier rate. That means your savings by switching to TOU would be even greater.

Yep, that's kind of my point. It's one thing to average out the month, it's quite another to evaluate actual use. Some can be modified to fit within the low rate period, and some can't be avoided.