Is a smart electricity tariff worth it?

(Long and data-filled post ahead!)

I've switched to energy provider Bulb (£50 off if you join using that link). They offer a "peak time" electricity charge which looks like this:

Graph showing peak usage between 16:00 and 19:00.

  • 23:00 to 07:00 = £0.0815/kWh
  • 07:00 to 16:00 = £0.1235/kWh
  • 16:00 to 19:00 = £0.3263/kWh
  • 19:00 to 23:00 = £0.1235/kWh

By contrast, the standard tariff is £0.1359 per kWh. That means my electricity is 2.4x more expensive for 4 hours per day, during peak time. But cheaper the rest of the time.

Let's look at a typical(ish) day's usage. This is what our home monitoring says we consumed on February 28th.
A graph of energy consumption.
If we ignore the solar power and battery storage, this is the result:

  • Normal tariff = £0.95/day
  • Smart tariff = £1.06/day

Ooof! Considerably more expensive. We come home in the evening and start cooking and watching TV right on the peak schedule.


We have solar panels. When the sun is shining, it reduces consumption from the grid. If the amount of power generated by the panels is greater than or equal to our home's energy usage, the meter stands still and we don't get charged.

This is what happens when we sum in the solar power:

  • Normal tariff = £0.68/day
  • Smart tariff = £0.91/day

Yikes! Dramatically more! During the daytime, we import virtually no electricity. Even when I'm working from home, the sun provides most of our needs - so we wouldn't benefit from the cheaper day rate.


We also have a 2kWh solar battery. When the solar panels generate more power than the house can use, the battery is charged. When we're importing electricity, the battery slowly discharges. Let's sum in that as well.

  • Normal tariff = £0.60/day
  • Smart tariff = £0.76/day

Quite an impressive drop. The battery tends to discharge in the early evening, after the sun has set. So usually peak time for the Bulb tariff. With a bigger battery, we'd save even more in the evening.

Based on this average(ish) day in February, you might think that the smart tariff isn't right for our set up. But that's not the whole story. Let's take a look at a few more interesting days.

Car Charging

We have an electric car. I'm using a regular 13 amp charger (3kW) - rather than the fast (7kW) charger. Here you see the car being charged to full over the weekend - right at peak time:

Graph showing lots of energy consumption in the evening.
Solar power was also pretty pathetic those two days, and there wasn't much in the home battery.

  • Normal tariff = £3.15 for two days
  • Smart tariff = £2.97 for two days

Aha! Even without shifting my car charging time to be after 19:00, the smart tariff could save us money.

Very roughly, if we'd deliberately not plugged the car in until after 19:00, the cost for two days would have been £2.26!

A whopping saving of 45p per day compared to the regular tariff.

Changing behaviours

And that's kind of the point, isn't it? If we shift our energy usage a bit, we get a significant saving. Can our lifestyle cope with waiting until 19:00 to start cooking? That sounds doable.

Can we set our battery to prioritise those peak times? Moixa - the manufacturer - have said they can set the battery to be aware of tariff rates.

Do we need the car to be fully charged? Nope - telling it only to charge in the cheap hours works for us.

If we're willing to change, our power bills drop.

Big Exhaustive Data Crunching

Over 2017-2018 I recorded all of our energy usage. I used it for graphs like this:

Here's what happens if we compare the Bulb standard tariff with a year of data.

There are a couple of caveats. Previously we charged our car with a 7kW charger. We've purchased new electronics and appliances which are more efficient. We also have a part-time lodger. So the energy profile isn't identical - but hopefully illustrative.

  • Normal tariff = £386.93
  • Smart tariff = £321.83

Assuming my calculations are correct - and I've got my daylight savings time the right way round - we could save a fairly hefty sixty quid per year!

With some lifestyle tweaks the savings could be even greater.

If you'd like to take advantage of this smart tariff, switch to Bulb (we each get £50 if you join using that link).

7 thoughts on “Is a smart electricity tariff worth it?

  1. Spiney Norman says:

    I worked on a project related to this for the state of California, back when they were originally trying to justify peak hour pricing (which happened at random hours; generally when it was super hot out and everyone turned the AC on) and smart grid stuff. The result published was that all of this sort of thing miraculously worked and people optimized their bills, theoretically allowing the power company to retire the expensive jet engine generators they used for peak days. If you looked more carefully, you'd see there was high compliance the first peak day, and pretty much none after that. Of course when they published their result, it looked great; I assume they justified dropping some of those non compliant days somehow. Anyway, there were billions in grants and investment dollars at stake, which is probably reason enough to fudge the stats.

    Hindsight it was super obvious what was happening if you had been to those parts of the state, and looking at the temperatures. Megastores were turning off their airconditioning when it was hot out in crazy desert places -at least the first time, after installing the fancy smart grid hardware. This was not, as they say, sustainable, so they didn't persist.

    Anyway, your doing an hours long data science exercise to get best use of your new power plan made me think of this. I mean, it's obvious you're a motivated user with investments in your own personal power grid. I'm trying to imagine my grandmother doing this.

  2. JohnU says:

    So you can save £60/year, you don’t mention how much the smart battery and solar panels cost?

    Even without solar, I could imagine fitting a smart battery to my house to absorb peak demand and recharge at the lowest rate – but you’ve got to save a LOT of £60’s to pay for a £1000 battery pack.

    1. says:

      We already had the panels and batteries - you can search this blog for pricing details. I didn't include them in this post because prices are highly variable. A local installer will be able to give you a quote for both.

  3. Neil says:

    Very interesting. I think you are right about the behavioural nudges based on the current timings for the tariffs. But if the peak period stretches until 19:30, or 20:00, would you still be prepared to wait to cook dinner?

    I get the principle of re-scheduling less time-sensitive things (eg as long as the car is charged for when you need it, it matters less when you charge it - or it’s unlikely to be a problem if you run your dishwasher or washing machine at night), but I’m more sceptical about readjusting one’s life around whatever happens to be that day’s energy pricing model.

  4. Paul Moxhay says:

    I have solar panels and although a saving may be possible by me switching to Bulb's Smart Tariff the problem I have is the scale of that saving verses the amount of effort needed when time-shifting our activities. Like you, our solar panels means we import very little during the day so the biggest savings then would only be achieved by time-shifting activities we would normally do during the peak time to one of the cheaper times and the only activitiy we regularly do during peak is cooking dinner. Unfortunately, like most homes, we cannot do that earlier or later on a regular basis as it is then that the kids come home from school or we come home from work.

    Obviously, having solar panels means we want to do our bit to help but the Smart Tariff from Bulb is not going to help many households save money I suspect.

  5. Thanks for this.

    As a bulb customer, I have moved over from EDF’s smart meter tariff and onto the standard plan with Bulb.

    I considered the Smart Tariff, but that Peak-Time jump is monstrously high. Like you, our family becomes more active from 4pm. 3/4 of the family are home then (or getting there) and we are cooking, cleaning and getting ourselves settled. A move over to a 7pm cook isn’t a viable option for us (we’re all different), and I don’t think a blanket ban on the washing machine between 4pm and 7pm is going to fly.

    Even without a detailed track of my usage, I know that the majority of the energy we consume will be around that peak moment, with very little being used in the off-peak time. I suppose we are exactly the type of users they modeled their tariff on – we are more likely to spend MORE on the smart tariff than the regular – especially if we don’t or can’t make enough Energy Changes to make use of the lower off-peak prices.

  6. AFG says:

    Hi, sorry to resurrect this post from 2019... but in the current context it can become more relevant than ever.
    (Historical notes for the future: in autumn 2021, there was a general price hike for energy in the whole of Europe -UK included-, about +20% in six months. It may hopefully go down, but for the sake of it, let's check if we can be smart with energy and reduce carbon yada yada yada....)
    2 good points were asked in the comment:
    * Spiney Norman asked about the grandmother who don't get all the intricacies of smart metering: it's a good question, but I think that we are starting to see an iPhone-esque advancement to smart energy use (including a push by Apple itself) making it more easy to use.
    * JohnU pointed to the crux of the problem: without battery, smart tariff are of no use. Considering the battery cost, smart tariff are of no use. As the blog owner (@edent) said he already had the batteries and the solar panels, so he pushed aside the argument. But, I think the problem is still valid: the batteries are there for a few year, making the cost spread in time. Let's say the cost is £1000, spread on 10 years: that makes £100 per year. My question is: these £60 of economy, could you stretch them to the tipping £100 point, or is it completely impossible?

    For this, I think we need a simpler installation and interface, and some automation to get everything working together. ALCS is a good start, smart heaters and thermostat a must-need. Automatically knowing when the rates are going up or down is the basic point. But this (car charger, smart heating,...) adds a cost to the system.

    As a user (and a power one), do you think the whole thing could become economically sustainable? And by the way, how do you know when are the peak hours?

    (side note: I'm so curious to know if the historical note I put at the start will become a glitch in the larger history -energy prices staying reasonable- or a non-concern -free energy! low prices!- or a joke in a future context -energy crisis becoming a major post-apocalyptic problem-; time will tell for sure, but I'm curious.)
    [by the way, mechanically, at the time of writing, the £60 are already £72 -20% price hike-)

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