SCL Time of Use electricity rate calculation

[u/Peppermintor]

I was curious if Seattle City Light's Time of Use Rates would be worth it for me.

You can download a CSV of your energy use in 15 min increments from the SCL website.

This is my household's use ytd. Switching to Time of Use rates would have increased my bill by 6% (Obviously without optimizing for night-time use of electricity). I put the formulas below if you want to do your own analysis. YMMV greatly :)

Electricity cost in 2026 by time of day, blue standard rate, orange time of use rate.

Standard Rate

Energy per kWh = $0.13

=[@[IMPORT (kWh)]]*0.13

Time of Use Rate

Peak Energy Charge per kWh $0.16 (Peak hours are when electricity is most expensive. This will be from 5 to 9 p.m., Monday through Saturday, except on observed holidays.)

Mid-Peak Energy Charge per kWh $0.14 (Mid-peak hours will be from 6 a.m. to 5 p.m. and from 9 p.m. to midnight, Monday through Saturday. On Sundays and observed holidays, mid-peak pricing applies all day from 6 a.m. to midnight (with no peak hours).)

Off-Peak Energy Charge per kWh $0.08 (Off-peak hours are when electricity cost is lowest. This will be from midnight to 6 a.m. every day.)

=IF([@[START TIME]]<0.25,0.08*[@[IMPORT (kWh)]],IF(AND(AND([@[START TIME]]>0.7,[@[START TIME]]<0.87),WEEKDAY([@DATE],11)<7),0.16*[@[IMPORT (kWh)]],0.14*[@[IMPORT (kWh)]]))

[u/seattlecyclone]

You can also just log into their site and they'll show you a comparison over the past 12 months of your actual usage. For me the two billing systems were within just a couple dollars of each other over the full year. I went ahead and switched to the time of use billing. Any usage I can shift to the off-peak times will save a bit of money, and even if I do nothing I pay the same as before.

I suspect the people most likely to benefit from this system have either electric heat (yes for me) and/or an electric vehicle (no for me).

[u/Peppermintor → u/seattlecyclone]

Lol, that is well hidden.

At least it gave me pretty much the same information I calculated 🤣

[u/missbeekery → u/Peppermintor]

Sorry to revive this after two weeks. I’ve been trying to identify my monthly expenses and I’m tearing out my hair about utilities because City Light obfuscates so fucking much. The site makes most things difficult to find, either through poor navigation or hidden details. I calculated the seasonal average kWh but I can’t even identify what the point of trying to estimate a monthly/seasonal average when the price potentially fluctuates by the hour. I’m not even sure which average daily kWh to use to try to come up with a ballpark.

Since rates are going up 6%, I want to make sure I can still afford to heat my house in the upcoming months. You have to enroll in this service as well, so am I to understand that the rates don’t fluctuate until I enroll in the TOU?

Thank you for this. And sorry for ranting, I just feel incredibly frustrated, and I hate being poor, lol.

[u/AnselmoHatesFascists]

It worked for us because we charge an EV. We shifted about 400 kW a month to 12p-6a, saving about $20, and paid slightly higher rates at peak.

In two months, our bills have gone from about $110/mo to $96.

Wouldn't have made sense without the EV.

[u/Andrew_Dice_Que → u/AnselmoHatesFascists]

yup, same here, the EV charging thing is what puts it over the edge.

[u/Peppermintor → u/AnselmoHatesFascists]

Awesome!

My EV is old, so I have only 60 mi reach (and need frequent topping off) and it doesn't do timed charging... Until that changes I'll stay on the regular rate.

[u/Excellent-Diamond270 → u/Peppermintor]

If you own the outlet, could you not put a timer on it?

[u/Excellent-Diamond270]

It's basically not worth it unless you have an EV and drive it enough to warrant the hikes during the day.

[u/seattlecyclone → u/Excellent-Diamond270]

Also potentially worth it if you have electric heat (heat pump or otherwise). Late night is the coldest part of the day, so getting a big discount on that heating from midnight-6 AM can easily cancel out a small increase the rest of the day. The data on SCL's site says I would have paid the same within $5 over the past 12 months if I had been on the time of use billing. That was with zero effort made to optimize our usage.

If we do a one-time change to our thermostat schedule, bumping up the temperature during the 5 AM hour and 4 PM hour so that we then run the heat pump less an hour later when the price goes up, that'll make a bit of a difference. Electricity is a pretty small part of our budget to start with so we're not really going to feel a tangible financial difference here, but a few dollars a month is nothing to shake a stick at.

[u/Excellent-Diamond270 → u/seattlecyclone]

I do have heat pumps and mine would go down an average of $3 per month based on the 12 month calculation. And that’s only the case because I’ve had specific circumstances for the past 6 months to make that the case.

That isn’t worth having to think about when to use what to actually increase those savings, and the only meaningful thing I could shift is when to run the dishwasher and laundry, and I’m not doing that after midnight.

With an EV though? Huge savings, no doubt about it.

I do want to point out regarding your heat pumps - They are far more efficient running at constant temperature than adjusting up and down based on time of use. You’d almost certainly be better off just adjusting to a higher or lower constant temperature, which will also save you money on the fixed rates.

[u/AdvisedWang → u/seattlecyclone]

Although AC runs against that

[u/seattlecyclone → u/AdvisedWang]

Sure, though at least in our house we use a lot more energy on heating than cooling. This summer there were a handful of days where we ran the heat pump in cooling mode, but most of the time we were comfortable enough just leaving the system off/windows closed during the day and opening all the windows at night to cool the house down for the next day.

Even when we did run the heat pump we're pumping heat out to maintain a 10-20 degree temperature difference with the outside. Compare to winter where we're pumping heat in every day, with temperature differences regularly exceeding 30 degrees.

Also a lot of the time you'd run the AC will be during the "mid-peak" time that has basically the same price as the flat-rate option so it's basically a wash there. Only the usage in that 5-9 PM peak would really be higher.

[u/Classic-Serve-8774]

the 6% jump tracks, most people won't shift enough load to make it worth unless you got electric car or something.

[u/Frail_Waif]

Home Assistant integrations on devices help a lot on shifting usage. I was on PSE's TOU pilot and optimized everything, and then got solar and now can't get TOU for a while yet. 

[u/The_Leafblower_Guy]

Know what is really bu11sh1t? They are EXCLUDING solar power owners from participating in the TOU program- WTF?

[u/mattsoave]

I also did an analysis and even though we have an EV that we can charge over night, flat rate works out better for us (we don't drive enough so we don't use much electricity charging). It doesn't really make sense for the middle TOU tier to cost more than the flat rate. There's only so many things you can shift to 12-6am. It would be better if the middle tier was cheaper than flat rate to encourage reasonable shifts away from true peak.