Insulating an Aga - Does it work?
UPDATE - Due to the increase in electricity costs and that the insulating didn’t really seem to work as well as we had hoped we have replaced the Aga with an electric range oven. And no, I am not happy about it!
And for those asking were we able to sell the Aga, the answer was no. We had it removed free of charge. Which was £500 less than some companies were quoting to remove it. Aga Steve did a great job and I would really recommend him for your Aga needs, whatever they are!
Basically our current costs are about £340 per month and this is likely to increase to almost over £600 per month or £7,500 per annum.
As we own an electric 3 oven Aga, 13 amp with AIMS, we were always aware that running costs are pretty high, roughly £40 a week. So with the increases in electricity prices looking like they are likely to remain (or get worse) we did some rudimentary maths and figured it may be worthwhile getting the Aga properly insulated.
We run the Aga on ‘Normal’ mode daily from 7.30am until 8pm and ‘Slumber’ after that. So on full blast for 12.5 hours and slumber for 11.5 hours.
The main thing to consider before getting the work done, could we do this ourselves or should we get someone in to do it? On the face of it an insulation kit for approximately £120 to £140 seemed doable. I am reasonably handy so had a look at the instructions and process for installing the insulation and thought I could manage it. However, it really needed two people to loft the hob off and back on again. And as we are a holiday cottage we were limited on available downtime, so if anything went wrong it would mean cancelling our guests.
So with that in mind we decided to use Yorkshire Home Heating who promised a one day turnaround, although we did need to switch the oven off 24 hours before hand to cool down. So in effect it was a two day process.
Ceramic Insulation process
The process of installing the ceramic insulation took two people about 3 hours including a full clean of the oven.
Dirty Aga! Clean Me!
So this was the Aga after a fair bit of use since it’s last full clean two years ago. that roasting oven has seen some action!
Love how the hot plate still looks pristine.
Vermiculite being removed
The hot plates exposed and Vermiculite being removed. This mostly involved an industrial strength vacuum cleaner as the majority of the vermiculite would be going back in.
The top level ‘blanket‘ was also removed and replaced later.
Clean Aga!
This is what a clean Aga looks like. won’t last long of course but that’s fair enough.
Most of out guests are happy to use the Aga in some way or another and of course it does provide great background heat.
running costs - pre insulation
As before this is a normal house, so it’s not an exact science but this is how much energy we used on a sample couple of days with the Aga on and the Aga off.
Aga On - used 39 Kilowatts at a cost* of £7.66 for a 24 hour period (9am to 9am)
Aga Off - used 7 Kilowatts at a cost of £1.38 for a 24 hour period (9am to 9am)
Extrapolate out this becomes 1,209 Kw per 31 day month and therefore £237.46 per month
However, the monthly average for the year was actually 1,103 kw, or £216.60 per month
*Current tariff is £0.1964 per Kw
running costs - post insulation
After the new insulation we used between 28 and 32 Kilowatts for two days measured. So lets say 3o Kilowatts a day.
So a drop of 9 Kilowatts per day from 39 to 30 equates to a 23% drop!
But this was just a quick snapshot between guests visits. so bear that in mind.
did we use less electricity by insulating our Aga?
Before we get into that, although I am sure you will have checked out the graph below, here is our very ‘complex’ methodology for measuring the impact of the insulation work.
And it is important to point out that it has been really hard to compare like for like usage year on year as there are so many variables. We anticipate that in April 2022 we will start to do more realistic comparisons with April 2021 and so on. Various reasons for this, see below, but until April 2021 we only had the Aga on full blast for one hour a day whereas since November 2021 it has been on ‘'full’ more often as we had guest staying. Hope that helps, I’m confused at the best of times. Also, guests tend to do different things with the Aga, for example some have turned off the gas heating and opened the hot plate lids to get heating into the house. No idea why!!
We had previously measured each months total kilowatt usage, so that was for the Aga and everything else in the house that used electricity. So there are lots of variables, eg weather, how often the hairdryer was used, were the kitchen doors left open, TV’s in use, garden strimmer etc - so this is not an exact science. And as you can see in September this year we had someone charging up their Polestar electric car, so that bumped up the wattage used!
And each ‘month’ is not exactly a calendar month - so look at the overall picture rather than be too specific.
However, it is real data from the real world so provides an indication of what the impact was for our house as it is used being let out as a holiday cottage.
We will update the graph each month over the next 12 months to we get a better idea of just what the benefit and costs were.
Hopefully for any of you considering going down the route of some sort of insulation process will be able to use this info to guide you in some way.
the results!
Kilowatts used per month
august readings in
Although we had an electric car staying it only added 88 kw so no idea what happened to make such a large increase this month. There were a few extra days as we couldn’t get a reading for exactly one month but I suspect guests may have been using extra heating although this was during a heatwave!
march readings in
Ok, on the rise again even accounting for 122 KW used by the radiator. But as before, still not a real like for like so it is going to be April before we really get those figures as this was when we opened last year post Covid restrictions. Cant wait! Particularly as unit costs are rising by so much in April.
February readings in
We saw a slight drop in the number of Kilowatts used from 1,085 to 1,077. The only thing I would note is that this year we had a few more guests in so the Aga was on for a greater length of time on a number of days as were the electric radiators. So possibly encouraging signs of savings!
january readings in
Well, allowing for an electric radiator which was on full time for 3 weeks the amount of Kilowatts was up slightly from 1097 to 1175. Again hard to know exactly what I was running last year in terms of was it on slumber mode?
december readings in
Hmm, interesting. I took the reading and it looks like even allowing for an electric radiator usage of 108kw we actually used an additional 172Kilowatts this year in December. Mitigating factors may be a 4 day power cut (ok, less KW used in theory but more needed to start up from cold?) and it was definitely colder this year than last. But even so, not sure why we used more power this year than last. One thing we have done is turn down the temperature dial within the Aga but still maintain the correct temperatures within the ovens and hot plates. The experiment continues and while only two months in I am yet to be convinced. I will take a couple of daily readings when I can so I get a better idea of daily usage.
November readings in
So first month and the kilowatts used have gone up! Hmm, now this could be because we had the electric heater on in one of the rooms, approximately 50 kilowatts per month but probably only on for half that time. So maybe shutting down and re heating the Aga may have had an impact that required more heat? Both billing periods were 26 days. Maybe it was cooler this year? Well, these are the figures so lets see how this pans out over the next few months!
Background heat pre and post ceramic insulation installation
So how did this insulation process affect the background heat? After all, reducing the heat being emitted would reduce the heat loss from the Aga and therefore would mean less heat in the kitchen and a lower humidity?
So here is what we found:
We tracked the temperature and humidity of the kitchen for a 48 hour period before and after insulation of the Aga. See graphs below.
Pre Insulation: Average temperature was 18.8°C with a high of 19.8°C and a low of 17.7°C
Post Insulation: Average temperature was 19.7°C with a high of 19.7°C and a low of 17.6°C
So basically not a lot of change with only a 0.1°C drop in average and minimum and maximum temperatures.
Pre Insulation: Average humidity was 59.3% with a high of 64.1% and a low of 53.1%
Post Insulation: Average humidity was 65.2% with a high of 68.6% and a low of 62.7%
So slightly higher humidity post insulation, which may well have been atmospheric.
We were lucky that the ambient outside temperatures were very similar varying between 5°C degrees at night and 12°C during the day this November.
So no noticeable change overall pre and post insuation!
Below is the temperature and humidity comparisons post insulation. Not a massive change all round! Which is good, I think!
We used the Govee room Thermometer and Hygrometer to get our temperature and Humidity information.
Super easy to set up and use via Bluetooth and an app on your mobile phone. Click below to have a look at the one we used (the first one)and their range of instruments including a digital meat thermometer which is very handy to have to use with your Aga.
summary so far - was it worth it?
Even with Decembers increased usage I am still being swayed by the real time test I did on a daily basis which was true comparison. So probably, particularly if electricity prices continue to rise which looks likely in April once the electricity price cap comes into play again.
I was hoping for a 20% to 30% reduction of Kilowatt usage based on an estimated ‘up to 50%’ reduction, albeit that was never guaranteed and of course there are a bunch of variables both on an Aga to Aga basis and my somewhat sketchy analysis.
I am inclined to look at the day to day direct comparisons I was able to run which showed a 23% drop which seems reasonable.
So things at this stage are looking promising notwithstanding this Novembers Kilowatt figures as there may things out of our control there. My back of a fag packet estimation of a 7 to 10 month break even point are looking about ok, may be sooner if prices go up.
And if nothing else if I keep the Aga for a couple of years the insulation will have paid for itself and more.
I am still erring on what to do regarding oven, heating and hot water at the house. A ground source heat pump is a non starter in a property like this, no cavity walls and while some insulation is in place its hard to be right on top of things without a complete rebuild of the property, which does date back to 1750.
And oil also looks like a long term issues notwithstanding the conversion changes from a gas boiler system.
So here we are, watch out for regular updates when I will update my break even forecast and current usage.
And please do email here or leave a comment below if you have any questions on what we have done here.
Thanks for reading this far if you have made it to here.
Feel free to share this info with whoever you like, you never know it could help somebody!