Heating With Electricity Instead Of Gas

When we first had solar installed, I really didn't envisage it leading to us switching to using electricity for heating over winter - after all, the sun doesn't shine very much, heaters are pretty energy hungry and mains gas was quite a bit cheaper than mains electricity.

However, my perception of the viability of using electricity to help heat the house shifted once we moved away from fixed rate tariffs and onto Octopus Agile. Plus, of course, using heaters to consume the free electricity delivered in a Octopus Powerups really has been something of a no brainer.

In fact, having Solar probably doesn't really factor into it much at all. We switched to Agile because the battery allowed us to load shift, but it plays no real role in running electric heaters in the evening.

In this post, I'm going to write a little about the approach that we've taken this winter, along with some issues that we've encountered along the way.

Localised Heating - Gas

There are rooms that, at certain times, we want to be much warmer than they usually would be.

The living room is one of those - it's all but abandoned during the daytime, but in the evening, we often want it to be much warmer than the rest of the house is likely to be. Although we could perhaps achieve this by using smart radiator valves, it doesn't really seem to make sense to pump heat around the rest of the house for the sake of one room.

In the winter before last, we used a 3kW portable gas fire to provide on-demand additional heat

Photo of the catalytic portable gas fire that we sometimes use

During that winter, in particular, having this fire available made quite a lot of sense: Liz Truss's government had recently shafted the economy at a time when gas prices were already rocketing and there was talk of possible shortages and brown-outs over the winter, so having some sort of heat "in reserve" felt like a prudent precaution.

As it turned out, there was also a shortage of butane bottles and Calor were refusing to issue new contracts: we had to fit the heater with a propane regulator instead so that we could make use of the bottles that were available.

Although having this heater made some non-financial sense, there's no escaping that bottles are an incredibly expensive way to buy gas:

  • A 13KG bottle of propane costs £52.50
  • 1KG of propane contains 14.019 kWh of energy
  • A 13KG bottle therefore contains 182.247 kWh
  • This means that the cost per unit is £0.288/kWh

By way of comparison, even back in 2022, the cost of mains gas was £0.103/kWh (although that was artificially lower as the result of the Government introducing a temporary cap).

Localised Heating - Electricity

I knew that we'd want some kind of localised heating again this winter: one of the things that stuck in memories of the previous winter was just how cold the living room had been on the evenings where the gas bottle ran out mid-evening.

With the gas heater having an effective unit rate of £0.288/kWh, there was a lot of scope for electricity to end up being a better option. The average rate on Octopus agile is (sometimes, quite a bit) less than that:

Graph showing mean, min and max agile prices since the end of November. The average is often less than 20 pence

Of course, that lower average doesn't help us much if it's a product of low pricing at times where we won't really need/want the auxiliary heating.

Luckily, on most days, that isn't the case, with the pricing profile looking more like this

Graph agile price throughout the day. There is a small peak in the morning, up to about 20 pence, then prices remain low through the day until about 4pm where they shoot up to nearly 40p before coming back down for about 8pm

The end of peak pricing varies a bit day-to-day, but as a general rule of thumb peak prices run between 1600 - 2000 (leading to our adoption of the memorable phrase used to discourage tumble dryer use during this time: "4 to 8? Don't do it mate...").

By mid-evening though, electricity prices are generally down to a level that means they're extremely competitive with the price of bottled gas (and sometimes even mains gas).

A Smart Radiator

We actually already had an electric heater in the living room - it's a wood-burner style thing which was here when we moved in. However, it doesn't have a thermostat, so I didn't feel comfortable automating it's use - I want to be sure that if the room is getting too warm, the heat source will turn itself off.

Instead, I bought a smart panel heater:

Manufacturers photo of the electric panel heater that I bought. It looks really thin in the photos but is actually about 8cm deep

I chose this heater based on a number of factors

  • It was wall mountable
  • The listing mentioned that it was controlled with the Smart Life app, which meant it could be controlled by Home Assistant
  • Whilst it was definitely more expensive than a simple oil radiator, the price wasn't exorbitant
  • It has a thermostat and the ability to adjust consumption rate (there are 3 modes)

At the time, it seemed pretty ideal for our needs.

With the benefit of hindsight, though, there were some drawbacks:

  • Because it's a convector, it doesn't really radiate heat: as a result, it can take quite a while for the room to actually feel warmer (we've got quite high ceilings, so there's quite a bit of air to warm before the sofa inhabitants start to feel the beneft)
  • It's silent when heating, but once the thermostat kicks in there's sometimes an annoying creaking as the element begins to cool and contract
  • The polished glass front is an absolute fingerprint trap
  • It beeps when the settings are changed remotely, so can't really be moved into a bedroom

I think, if I were doing this again, I'd probably address our needs a little differently. It'd make a great heater for elsewhere in the house, but the living room could probably do with either an oil, infra-red or a fan heater.

Access to the Manufacturer's platform

In the last few days, we've also run into something that's a much bigger concern.

When I was first looking at heaters, one of the key components of my decision to buy this one was that Smart Life devices could be controlled via Home Assistant - Tuya's documentation even detailed how to link the two.

This week, though, we lost that ability.

A little hunting around revealed that we were not the only ones with the root cause given a little further down the comment thread

has your Tuya Cloud IoT trial period expired? Mine apparently expired in February but API access was only disabled today. I had the same issue as you and renewed my access and everything works now.

I think they are doing a batch disable for API access of all expired Tuya Cloud IoT services. Renewal is free, just follow the steps here

The devices are made available to Home Assistant via a Tuya package called "IoT Core", however, it turns out that that package was only running on a trial basis. This came as a surprise, but it is possible that I might simply have forgotten: the wayback machine shows that the docs did mention it around the time that I was setting things up:

For now, you can extend the trial period multiple times. However, Tuya does not promise it to be permanent. As the integration will make relevant adjustments accoding to the Tuya IoT Development Platform rules in the following years.

Running an IoT platform costs money so, whilst frustrating, it's not too surprising that Tuya might decide that they can't offer it for free forever. Of course, one could also argue that, given the premium charged when purchasing "smart" devices, the cost of running the service is already priced in.

Either way, I have some gripes about the manner in which this unfolded:

  • We lost access with no notice (no email, no app notification etc), it was just cut off.
  • As a result Home Assistant was unable to turn our heater back off - something that's potentially expensive and dangerous (in this case, though, it was while we were in the room so it didn't go unnoticed) - sudden cut-offs are really not a good idea in services used for automating heating appliances.
  • Although there is an option to extend the free trial, it l has to be approved manually, which takes time
  • Once the trial extension has been granted, Home Assistant needs to be restarted for devices to become usable again
  • After Home Assistant was restarted, the device re-appeared but with a new name (breaking existing dashboards and automations) - that's not Tuya's doing, but it is an unwanted side effect of the way they cut access (rather than denying access, the API just stopped listing devices)

I have no particular issue with paying for a service that's provides us with some benefit, however, Tuya's pricing structure clearly sn't tailored towards individual users:

Tuya's pricing matrix. Packs are trial edition, flagship edition and corporate edition. The difference in allowances between trial and flagship are huge. There are no prices in this table

This is made worse by the fact that there's no set monthly price for any of the editions, they all charge per million API calls.

The pricing tier associated with the trial edition charges $3.71 per million. Tuya's reporting suggests that HomeAssistant made about 40 API requests per day in February:

Tuyas API Statistics graph, it shows we made somewhere between 30 and 40 requests a day

Maintained over 31 days, we'd be looking at 1240 requests per month, which is well within the allowances of that tier.

So, does that mean that using the paid version would cost me $3.71 a month? Erm... no.

Tuya don't seem to provide a way to purchase that plan - the plan purchase page only offers it as a one-month free trial (the clue's in the name of the tier really).

That means that, if I wanted to pay, I'd need their Flagship edition. It's cheaper per block of million requests, but you pay a commit upfront for the allowances, making it... erm... somewhat expensive

I put Tuyas IoT Core Flagship edition in my cart to get the price. It's 25 thousand dollars a year

Even if I suddenly somehow had 25 grand to spend on heating, I think I'd probably be more inclined to spend it on something like a heat-pump rather than on obtaining API access.

So, this means that the options available to me are

  • Spend 25K on API access (not really an option)
  • Stick with the free trial and put up with the service interruptions (calendar-ops FTW)
  • Plan to replace the heater

Although I'm frustrated with the situation that we find ourselves in, it is partly my own fault. I've grumbled in the past about the limitations that come with manufacturer controlled systems and have even built locally controlled solutions for other rooms. I can't really claim not to have known that the commercialised Internet of Things is something of a crap-shoot for consumers.

Realistically, we'll probably end up taking the third option and replacing the heater.

The Approach

Our heating already relied on quite a lot of automation, with the central heating being subject to a number of controls to expose two main features:

  • Normal daily schedule: warm when the house is in use, cooler when sleeping
  • Automatic Boost in target temperature if a bedroom falls below a threshold overnight

Some rooms also already had additional electric heating, so adding a new heater in the living room didn't pose too much of a challenge.

The overall approach was built around some simple rules:

  1. If prices are lower than mains gas, use electric heating
  2. If prices are lower than bottled gas in the evening, the living room heater can come on
  3. If prices are £0.00 or lower, increase the target temperature

The third rule was set with Octopus Powerups and Plunge pricing in mind

Screenshot of Octopus's description of Plunge pricing. When supply outstrips demand, prices drop and occasionally go negative.

When prices are negative, using energy reduces our electricity bill, which is an obvious incentive to help consume that surplus green energy.

With Powerups (where prices are £0.00) there's no impact on our electricity bill but, depending on the time of day, it can potentially help reduce our mains gas consumption.

During the working day, the central heating has quite a low target temperature set, which increases later in the day once others are likely to be in the house. Having a period of free electricity shortly before that has allowed us to use electric heaters to pre-warm the house - reducing the amount of gas that is needed to bring the house up to temperature.

I'll write more about the automations created to implement all this some other time.

The Outcome

Calculating the exact impact is actually a little tricky, because we don't have a smart gas meter. This means that the readings that I have are very much reliant on me remembering to read the meter (giving a somewhat irregular interval).

We do appear to have used less mains gas this winter than last: Our daily average usage is around 4kWh less.

However, we also used quite a lot more electricity:

  • Dec 22: 18.08 kWh daily average
  • Dec 23: 33.048 kWh daily average

Amongst other things, December's daily average is skewed by extremely heavy usage during power ups. To help calculate the cost of that additional electricity usage, we can look at a weighted average of the prices we paid for electricity

Weighted average price paid for our electricity, generally sits just under the 10 pence mark

This metric is calculated and stored by one of my downsampling scripts:

weighted_paid_price = total_stats["total_consumed"] / total_stats["total_spent"]

Even with the spike in cost around Christmas, the average price paid is £0.08/kWh.

We also need to calculate daily average consumption for the gas bottles used in Winter '22:

  • My credit card bill shows that I bought 3 bottles (567.78 kWh) across a period of 90 days
  • That would give an average of 6.3 kWh per day, but technically, the final bottle hadn't been used at that point.
  • Taking the consumption of just 2 bottles, the value is more like 4.21 kWh/day.

Finally, we need a unit cost for the mains gas that was consumed. To allow a 1:1 comparison of the difference between the two, we assign each the same price (taken from my 2024 bill): £0.06461/kWh

Cost of daily average Mains Gas usage:

Dec 22: 14.1925 * 0.06461  = £0.917
Dec 23: 11.0575 * 0.06461  = £0.714

Additional electricity for Winter 23:

14.968 * 0.08 = £1.197

Gas bottle gas for Winter 22:

4.21 kWh * 0.288 = £1.212

If we put those together, we get two numbers that we can compare:

Dec 22: 0.917 + 1.212 = 2.129
Dec 23: 0.714 + 1.197 = 1.911

We can see that this year appears to have worked out about £0.22 cheaper per day.

Omitted Variables

There's quite a bit that these calculations don't account for though:

  • Was the weather better or worse this year?
  • The gas heater only heated one room, but we've been using electricity to warm multiple rooms - so it's not truly a 1:1 comparison
  • Have we ended up using the electric heater more regularly (or for longer) than we would the gas fire?
  • Gas fires release humidity and carbon monoxide, so there are additional intangible costs there
  • The cost of the heater - we appear to have saved about £20 in December, so it'd take about 5 similar months to break even (but there aren't that many similar months in any given year)

Whilst it does appear that using the electric heaters have saved us money, the only thing that I can say for certain is that it has to be better burning n kWh of electricity at £0.08/kWh than burning the same in bottled gas at £0.288/kWh.


I think, overall, our use of electric heaters has been a success - if nothing else, it's certainly saved me from having to drive out and lug gas bottles about.

I'm not so sure, though, that the purchase of that particular heater can be characterised as much of a success: It was a fairly poor choice for the room and, as a result, has needed to run for longer than another heater otherwise might. Being able to use it the way that we want to is also entirely dependant on the whims of the manufacturer, which really isn't something that I'm on board with.

For obvious reasons, I'm wary of making purchases based on the availability of Octopus power-ups, but they certainly make some kind of storage heater more attractive - even if just something with a relatively small mass (like an oil radiator).

We've some time to plan, but I'm not sure that that heater will form any part of next winter's living room heating strategy.