I'm just casting around at the moment on costings, and wondering if it may be possible to replace my ageing existing log gas boiler with an electric equivalent.
If possible, I realise I would need a three-phase supply in order to get a boiler with sufficient output to feed a 2000l buffer tank. The beauty of the idea would be that everything else stays the same with only the heat source changing.
I wondered if anyone had attempted this?

With a big buffer tank, surely a miluch smaller boiler could be used? Potentially even a 3 or 6kW immersion heater depending on heating requirements. Or are you trying to keep to off peak electric hours and therefore need a much bigger heater to fill the buffer tank in a short timeframe?

There's a few reasons why folk might want to store mains electric heat, what reason did you have in mind? That will tell you how many kW power you need, and how many kWh storage capacity.

If you want to store off-peak electric heat to heat the house, then add up how many kWh of heat you need on a cold day. Divide that by the duration in hours of your tariff's off-peak period, to give the kW power rating of the heater. Then, you need about 100l of thermal store for each 3-4kWh you need to store.

Eg if you only need 2.5kW to heat the house, so 60kWh of heat each day, and run on E7 with 7 hours of off-peak, then you need 60/7= 9kW heater and you need 60/3 *100 = your 2000l storage. You might be able to run your 9kW heater on 2-phase, or use 3x 3kW immersions.

But if you need more than 2.5kW to heat the house, then you can make the heater bigger than 9kW, so it heats the house and the store simultaneously off-peak. Or run the 9kW heater during peak time as well as off peak, at greater cost.

Alternatively, if you only want to store up DHW, a 3kW heater in that store will be plenty big enough.

Different tariffs have different off-peak hours, eg some EV tariffs have 2 supercheap hours, whereas Octopus Agile had about 15-20 somewhat cheaper hours (if it's still available).

In the long run, a heatpump might work out cheaper?

Thanks all for your replies.
I was musing over the idea of replacing one batch burn device, the 10-year-old log gas boiler, with another, possibly a small commercial, electric water heater. The current wood boiler is 42kW and replacing with a like for like three phase electric equivalent at about £1500-£2000.
An uneducated guess could mean install and wiring changes possibly add another £3-4000, possibly more.
The real fly in the ointment is therefore going to be three phase supply. The cable run is short as there is a three-phase supply on the post opposite my house, so under a rural village road and about 15metres to the current fuse box. The existing supply is, I'm guessing in ducting, but can't be certain. I've been advised it could be well in excess of £10,000 which would make the exercise a non-starter and another air-to-air split heat pump the better option.

Incidentally, I don't generally buy the existing wood as most of it is my own supply, but age is creeping up and processing logwood is a young man's game.
As I mentioned above, I just wondered if there was an easy replacement fix, as the existing hydronic system works fine.

Posted By: djhI'm not sure what 2-phase is?

2 phase is 380 V and will be taken by tapping into 2 phases of a 3 phase supply. It is used in specialist applications. I only learnt about it a few years ago when I was looking at purchasing a 2nd hand disc sander for my workshop and noticed the label. Then more recently I discovered my roller shutter door to my agri shed is powered by a 2 phase motor when my neighbour took out a phase. Seemingly they are also used in hoist application such as lifts but do not know how widespread they are. Also used in certain electric welding equipment.

Posted By: owlmanI was musing over the idea of replacing one batch burn device, the 10-year-old log gas boiler, with another

But you have a large buffer tank, the purpose of which is presumably exactly to allow the use of a batch burn device like your log burner to be used for a more continuous load. So why replace it like for like? Why not consider the end use of the heat and the requirements of the load and view the buffer as an extra resource that can be used if desirable, but definitely doe NOT need to be heated in the same way.

"split phase" is a thing. We have it. Iirc it's two phases, 180° apart with a shared neutral at 0V and 230V each so 460-480V between phases.

It's a pain really as 3phase is so much better set up for running big kit while split phase is relatively obscure. And you're supposed to make an attempt to balance the phases somewhat. Does give a bigger supply than standard single phase though and is generally seen on remote places. Must be cheaper than running proper 3phase to places.

Who said anything about running at 12kW continuously, simply there as a backup. Four x 3kw immersions wired separately give good flexibility. and two could be linked to a power diverter from my 10kW solar array. Like I said I don't want to heat 2 tons of water just enough to satisfy the respective draw of points, DHW and CH,

I have a property with a 12Kw electric boiler matched to a standard hot water tank. This is a 3 bed 2 bathroom property. It works very well but it costs a hell of a lot to run. Its a holiday rental so I can't control what guests do, at the moment (20c during the day and 18 at night) its around £20 a day. If guests crank it up to high 20's it can be well over £30 per day (35p current rate).

I only have a single phase 100amp supply and have added EV charging which has to be limited to 16amps at the moment due to risk of taking out the main fuse. I am waiting for a load balancer for that.

If you are going to go electric I think you really need to look at something that can use lower cost energy overnight, I am looking at TEPEO as an option for my place. I think this is about £6k but could mean most of my electricity use is at the lower night rate so could pay for itself in just a few years. There are a number of smart hot water tank solutions that can store heat or just heat what you need.

It sounds like you have a larger property, you can runs several of these boilers in parallel but that would need your expensive 3 phase supply.

I have to say if you main reason to change is the work of preparing wood to burn its going to be way cheaper to pay someone to do that for you but better for the planet to stop burning stuff if you can.