[sheepandponies]

Looking for some opinions on installing electric boiler as alternative to an oil boiler.  Building on to our cottage and existing boiler is too small for additional space so need to change.  One option is to install an electric boiler.  We have put 3kw of PV panels in the new roof and will probably install an electric ESSE for cooking. Dont know how much electric boilers cost to run.  Thanks in anticipation. 

[chrismahon]

I looked into fitting an electric boiler for one of my customers who was on a bottled gas system which needed major work. The boilers are small and are limited in size by the available power supply, so it may need upgrading. Good if you already have a central heating system with radiators installed but probably cheaper all round to fit electric radiators if you are building an extension, because the wiring for them can go in when the rest of the wiring is done.


Last time I did a comparison electric radiators were cheaper than oil, but then a new generation of condensing oil boilers arrived. The alternative is a new oil boiler (think they are Bosch) and a relatively simple extension to the existing central heating system. You will need to calculate the required output first, add a safety margin for future growth, then see what boiler you need. A lot will depend on the state of your current system -perhaps it needs replacing soon anyway?

[sheepandponies]

The system was brand new in 2003.  I am concerned about the running costs of using electric.  Oil (which is what the cottage has just now) is currently cheap but not that long since it was double current price and guess it wont stay cheap, but electricity prices continue to increase too!!!

[regen]

The only way electric will be viable is if you INSULATE to a very high standard and then there is a distinct possibility that the existing oil boiler will be big enough.

Regen

[sheepandponies]

Plumber doesnt think so 

[regen]

Get a second opinion from a heating engineer!

Regen

[chrismahon]

2003 is pretty old for a central heating system SheepandPonies and it depends a lot on the budget for installation and the quality of it. You need to do some proper evaluation and as Regen says look carefully at your insulation levels and see if they can be improved. it was around 2009 that the Bosch condensing combi-boilers were being fitted to Estate properties I maintained.


Went to view a property a while back and the loft had 400mm in it!

[sheepandponies]

The existing cottage has an EPC of C, and the new extensions will have so much insulation in them that they will be A rated.  The new extension has underfloor heating in the ground floor but radiators up stairs.  The existing cottage was rebuilt in 2003 and was up to building standards levels of insulation then....we will add more loft insulation in to 400mm.  The boler is a 40-65 btu output so deemed too small to deliver all the heating and hot water to the house when completed - 3 bed and 3 bath.  I have to consider the otions of using the existing boiler plus in new part adding in an electric boiler, OR replacing oil boiler with something bigger.  This has been a holiday let until now so boiler has not had a hard life!  Does anyone on here recently installed an electric boiler and if so what do you think of it and how much is it costing you to run?  Thanks for all the comments....learning curve for me 

[regen]

"The existing cottage has an EPC of C, and the new extensions will have so much insulation in them that they will be A rated."

From the info you already have and that you should have you should be able to come up with an annual KWH 

"The new extension has underfloor heating in the ground floor but radiators up stairs."

This has already been installed for a wet system? If so in an A rated building I doubt if the upstairs rads will need to be used as the UFH will probably send enough heat upwards. 


 "The boler is a 40-65 btu output so deemed too small to deliver all the heating and hot water to the house when completed "

Assume you mean a 40000 to 65000 btu boiler which equates to around 12 to 18kwh. Can the boiler be rejetted to give a higher output? what is the basis of the calculation which deems the existing boiler to be too small ?


 "I have to consider the otions of using the existing boiler plus in new part adding in an electric boiler, OR replacing oil boiler with something bigger." 

For which you need the annual usage for heating and hot water in both parts of the house and /or the services of a competent heating engineer.

Its not that simple - at the moment electric is 15p/kwh day rate and say 8p night rate. Oil is about 35p litre which allowing for a 90% efficiency works out at about 4p per kwh so oil could double before it overtakes electric on night rate. With half the house heated by oil and half by electric its difficult to say which will be the major supplier.

All i can say is that my gut feeling is that electric will always be more expensive and i know that I can easily heat a 140m2 1800s heavily insulated house at 800 ft using a wallstar 15 to 20kw oil boiler with UFH on half ground floor and the rads upstairs turned off and maintain temps in the 18 to 23 degs range and always have plenty of hot water on tap.

However I rarely use the oil choosing to do the job with a 21kwh WBS 18kwh to water and 3kwh to room.
Good luck

Regen

[juliem]

Oil now 25 p per litre here in Shropshire..

[chrismahon]

You can effectively boost your boiler output by heating water with night rate electric. This is how we added extra radiators in our house and kept the same 50,000 BTU boiler. Increase the size of your water tank and even better make it a mains pressure system S&P. You can top it up with daytime electricity if necessary, but we have never needed to.

[regen]

"Oil now 25 p per litre here in Shropshire.."

Now that is a good price and probably compares favourably with using your own firewood by the time you have cut and carted it.  Best i can get is 29.9p/litre delivered in west wales.

Regen

[Womble]

Unless something really radical happens to electricity generation, heat from electric will always be more expensive than other sources, as it's the highest 'grade' of energy we have available.

Be careful you don't confuse "KWh per year" (which gives you a rough estimate of your bills), and instantaneous KW, which tells you the size of the boiler you need to keep your house warm on a cold day. Also beware of these calculations, as the underlying assumptions may not match the way you actually live. We cheerfully heated our home through some very cold winters with a 12kW range and 8kW wood burner. However, when we had the calcs done, the requirement came out at 35kW, since they were based on keeping the whole house at 20degC during the coldest winter. Frankly we'd have to win the lottery before we even considered trying that one, and as a result, our actual energy bills are 20% of what the calcs said they should be!

If it was me, I'd insulate and draft proof as much as possible, then calculate the total instantaneous KW as accurately as I could (calculation spreadsheets etc are available, or get a quote for the whole place from a heating engineer, which will include the size of boiler. As per my experience above, it won't be perfect, but it's probably the best guess you'll get, and your lifestyle might be more 'normal' than ours  ). You can then work out the best way to achieve the total KW output from the heat sources you have available (existing boiler, new boiler, wood burner, whatever). One thought - if you would otherwise go with an electric boiler, how about electric underfloor heating in the new extension, assuming it's still to be built? If you also beefed up your instulation, would that give you enough total kW to keep your existing boiler perhaps?

Have you considered a wood pellet boiler though?  They do require a bit of space for a pellet store or similar and sometimes also a thermal store (big water tank). They are hence very expensive to install. However, at the moment, the UK government will pretty much pay for the whole installation for you over a seven year period, through the "Renewable Heat Incentive" scheme. (Just be aware if you look into this that there are some good reputable companies out there, and there are also some terrible ones. When we looked into it, we had a couple of salesmen round who were selling via deliberate lies and distortion. Buyer beware and all that).

Good luck!! 

[oor wullie]

I don't know anything about electric boilers but do they use single phase or 3 phase electric?  It might depend on size as I think a normal domestic single phase supply is only good for 15 or 20 kW.

I recently had a quote for a 3ph supply of £140k which changed the economic viability of my project somewhat!

[sheepandponies]

Once again thanks for all the responses.  We have access to 3 phase as have a supply to part of the farm, however this might be overkill?
Underfloor heating is going in downstairs which will be run off boiler.  Upstairs bathroom also underfloor but this will be electric to make most use of PV panels in summer so that we can leave our bathroom floor heated all year.
Was heating engineer that builder is using that thought our existing boiler would not be big enough, wondering how I can get a 2nd opinion at this time of year?