Replacing Oil Boiler with Electric

jez1234444

I live in a 1963, 3 bedroom detached bungalow which has double glazing, cavity wall insulation and insulated loft.
We have no mains gas where I live and I currently use an oil boiler to provide hot water (cylinder in loft) and heating (wall mounted radiators). The boiler is about 7 years old and works very well (88% efficient on last service).
I use about 1600 litres of oil each year which over the last few years has cost me on average £700 per year.
I use about 2,700 kWh of electric each year which costs me £360 per year.
I have just had planning permission to install a 6kW solar system in my garden. It’s south facing where my roof isn’t. The cost of the install will be about £7,000.
My basic question is, should I install the solar system and also replace my oil boiler? I know oil is relatively cheap at the moment and the solar FITs have been reduced quite a bit, but I’m trying to plan long term as I’ll be retiring soon and want to have my place as efficient as possible.
There seem to be many electric boiler options. I would be just looking at ones that could work with my existing wet system (hot water cylinder and radiator). Basically swop the oil one for electric.
Any advice or tips welcome.
Thanks

matelodave

A solar system will not provide you with sufficient electricity during the winter & spring to heat your house or hot water. They work when the sun shines and the days are longer in the summer which is the exact opposite of what happens in the winter. You therefore end up using most of your electricity for heating and hot water from the grid which you'd be paying full price for.

There are two ways of providing an electric hot water system - either using something like a hot water combi-boiler which heats the water as required - just like a normal boiler. This uses fully price electricity and will be very expensive to run 3-4 times the price of oil or gas.

Alternatively you could get a thermal store, which is a big highly insulated hot water tank that gets heated to a fairly high temperature overnight on an off peak tariff and the heat is extracted by the heating & hot water systems via heat exchangers. The store needs to be large enough to supply all your heating and hot water needs otherwise you'll need to boost it with expensive daytime electricity - which for E7 customers is even more expensive than a single rate tariff.

If you are going to be at home all day then you might find that you've run out of heat by the evening. The tank is also likely to be too big & heavy to fit in the loft so you'd need to find somewhere on the ground floor to accommodate it

I'd guess that your oil system is actually the cheapest way to heat your place.

You can work out how many kwh are in 1600litres of oil and then see how how much that would cost in leccy (full price and e7) because you'll need the same amount of heat to heat the place whether it comes from, gas, oil or electricity (possibly more if you are going to be at home all day).

There's about 9kwh in a litre of oil (88% efficient boiler) so 1600 litres = 14500kwh @ £700 (what you reckon you are paying = about 4.8p/kwh.

Full price leccy is around 12p kwh x 14500 = £1740. E7 is around 6-7p x 14500 = £870-£1000. Have a look on comparison sites to see what the cost would be where you live

I'm in a 1986 bungalow about 140sq.m, all electric and have a heatpump. 16 year old double glazing, cavity wall insulation and 300mm insulation in the loft. The heating runs all day and during the night if it's cold

I reckon my electricty consumption for heating & hot water is around 3500-4000kwh a year @ 12p/kwh = £450 but for that I get around 12000kwh of heat which equates to under 4p/kwh.

We are also at home all day and our total energy consumption for last year was exactly 6059kwh = £727.63 (single rate tariff)

macman

Swapping an oil boiler for an electric one is, bluntly, the economics of the madhouse.
As above, you can't store the solar PV energy generated during the day, so all it can do is possibly feed an immersion heater during daylight hours.

J_B

Ain't broke = don't fix???

jez1234444

Many thanks for the detailed advice matelodave.
My main interest is looking for alternatives to what I have at the moment, but if oil seems to be the best option then that’s fine, I’ll stick with it. I just get a little concerned when the price doubles etc.
My rough calculations for oil worked out about the same as yours (5p/kwh). This was based on an average over the last 3 years as I’ve paid between 56p/litre (Dec 2013) and 24p/litre (Jan 2016).
Do you use a ground source heat pump? I’m just wondering if this maybe a better option. I have quite a large rear garden (80m long) so installing a slinky system should be ok.
Would it make sense to install the solar and heat pump?
Assuming my heat needs are about 17,000 kwh (14,500 (oil) + 2,500 (current)), the cheap energy club quote £1,650 per year which does seem very expensive for a fully electric system.

matelodave

Mine's an 11kw Daikin Air Source Split system (outdoor compressor and indoor hydrobox) feeding a PolyPipe Overlay underfloor heating system stalled all over the bungalow. I estimate that mine has a COP of around 3-3.5(which means that for every kw of leccy that it consumes it produces about 3-3.5kw of heat. So my heat requirement is estimated at about 12000 kwh a year translates to (12000/3.5) = 3500kwh of electricity plus heating the hotwater = about another 750-1000kwh a year (we keep our hot water temperature quite low at 45 degrees to improve the efficiency)

Bear in mind that a heatpump whether ground source or air source runs at a significantly lower temperature than a conventional heating system- ideally around 35-40 degrees rather than 70+ than a boiler.

It's generally reckoned that for every degree above 35 that you run a heat pump it will cost another 2.5%. So running it at 50 dgrees could cost you 40% than running it at the optimum.

You need to make sure that the heat emitters (Radiators, underfloor or fan coil units) are capable of heating the place with the lower temperature flow - that generally means doubling the size of any existing radiators and possibly increasing the pipe sizing.

Just bunging one on an existing system will be a recipe for disaster - you'll be cold and it will cost a lot to run.

I'm also getting the benefit of the RHI payments - £700 a year for 7 years (£4900) to help offset the cost of the heatpump.

If you are interested in a bit more info you can PM me with your E-mail address and I can send you some info and photographs

macman

If oil (and therefore gas) prices were to double, then what do you think is going to happen to electricity prices?The bulk of the UK's power production will remain fossil fuel dominated for at least a decade to come-one new nuclear facility and some offshore wind farms and other renewables are not going to drastically change that mix.

Smiley_Dan

I would definitely stick with what you have and use the current savings on oil to invest in improving insulation and air tightness.

A PV system will provide you with hot water for most of (i.e. >50%) the year, but it's not a complete solution.

Having a cylinder in the loft is a very bad place for it. HWCs are very wasteful of heat, so it's unfortunate that heat isn't being lost into the thermal envelope.