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C
Rank 6
confused off peak b
Rank 6
February 16, 2026
Solved

When Economy 10 switches to off-peak, is all usage charged on the lower rate, or just the appliances hooked up to the off-peak register?

  • February 16, 2026
  • 4 replies
  • 228 views

I have a smart meter and am on economy. 10 tariff. My electric underfloor heating and immersion are connected to the meter via a consumer unit connected to port 5 and the rest of the electric useage is via a separate consumer. unit connected to port 1. The meter switches correctly to energize port 5 at the proper times, and port 1 is energized 24  /7. My question is when the meter energizes port 5 and I am charged off peak rate is the energy being consumed via port 1 being charged at the off peak rate as well or is everything still split by the meter so 1 is only ever charged at peak and 5 is only charged at off peak or is everything charged at the off peak rate and then when 5 gets switched off as per tarrif the meter charges everything still on at peak?

Best answer by Firedog

… if we leave the washing machine tumble dryer etc until after 1-00pm we wondered whether we would be washing at cheap rate instead of the morning on peak rate …
 

Yep, that’s one of the big advantages of the E10 plan - you can do all sorts of stuff at cheap rate during the daytime offpeak periods.

A word of caution: the switch to offpeak won’t happen on the dot (you wrote 1-00pm). Every meter has a unique built-in delay of a few minutes (theoretically 1 - 30 minutes, but normally in practice less than 15) just to make sure that a lot of heavy loads on a possibly dodgy network branch don’t fire up at the same instant. You should watch carefully to see just how big your meter’s delay is so you remember not to switch the dryer (or iron or electric shower ...) on until the switch to offpeak has actually taken place. The delay happens at the other end of the period as well, so you have a few minutes’ grace after say 4-00pm to finish the hoovering before peak rate starts again.

The late evening session has similar advantages: you could for example have a fan heater in the bedroom to get it warm and cosy before bedtime and possibly again in the morning if your first session is 4-30 - 7-30am. You could even use smart plugs to automate switching the heater and electric blanket on before bed for real indulgence.

4 replies

Firedog
Super User
FiredogSuper User
Super User
February 16, 2026

This is the way it’s supposed to work: at the start of an offpeak period, the meter’s internal switch (the ALCS) turns on power to the heating equipment on port 5, the meter stops recording on its peak rate register and starts recording on the offpeak register.  So yes, all consumption during offpeak hours is billed at offpeak rates. A single-element meter can only record what is passing through it on one register at once.

We have seen a few cases where this isn’t the case with new installations, because of an initial mismatch between the ALCS timings and the tariff switching timings. The fault is usually corrected quickly by remote control.

Why do you ask?

 

Noel | I have no official status; I'm just a volunteer who comes here to help other customers. My gear: Aclara SGM 1416-B Electricity-only E7 meter; Chameleon IHD3-PPMID-AAA | It may look as if I know what I’m talking about, but don’t let that fool you. |
C
Rank 6
confused off peak bAuthor
Rank 6
February 16, 2026

the eco 10 rate gives us 3 hours off peak in the afternoon so if we leave the washing machine tumble dryer etc until after 1-00pm we wondered whether we would be washing at cheap rate instead of the morning on peak rate even though the kitchen appliances are connected to the consumer unit fed by port 1. 

Firedog
Super User
FiredogSuper UserSolved
Super User
February 16, 2026

… if we leave the washing machine tumble dryer etc until after 1-00pm we wondered whether we would be washing at cheap rate instead of the morning on peak rate …
 

Yep, that’s one of the big advantages of the E10 plan - you can do all sorts of stuff at cheap rate during the daytime offpeak periods.

A word of caution: the switch to offpeak won’t happen on the dot (you wrote 1-00pm). Every meter has a unique built-in delay of a few minutes (theoretically 1 - 30 minutes, but normally in practice less than 15) just to make sure that a lot of heavy loads on a possibly dodgy network branch don’t fire up at the same instant. You should watch carefully to see just how big your meter’s delay is so you remember not to switch the dryer (or iron or electric shower ...) on until the switch to offpeak has actually taken place. The delay happens at the other end of the period as well, so you have a few minutes’ grace after say 4-00pm to finish the hoovering before peak rate starts again.

The late evening session has similar advantages: you could for example have a fan heater in the bedroom to get it warm and cosy before bedtime and possibly again in the morning if your first session is 4-30 - 7-30am. You could even use smart plugs to automate switching the heater and electric blanket on before bed for real indulgence.

Noel | I have no official status; I'm just a volunteer who comes here to help other customers. My gear: Aclara SGM 1416-B Electricity-only E7 meter; Chameleon IHD3-PPMID-AAA | It may look as if I know what I’m talking about, but don’t let that fool you. |
    C
    Rank 6
    confused off peak bAuthor
    Rank 6
    February 16, 2026

    thanks for you great explanation. we will take your advice and act accordingly.

     

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