Moving from Oil Combi to Electric heating

FredSomerset

Hi,
My oil combi boiler has packed up and needs replacing (£4,500 best quote). However, I have been panning to switch to a more sustainable and less grid reliant set up, and while I had hoped to do this next year, maybe better to just go for it now.

i have done quite a lot of research and this is my proposal. I would welcome feedback on whether this is realistic? If so, What considerations I need to take into account? And any products or sizing advice to consider in the set up?

Phase 1
Replace defunct oil combi boiler (18-24kw) with an unvented cylinder 210ltr, capable of producing DHW and CH, initially heated using eco 7 or equivalent off peak tariff (about 10p kWh which is similar to oil). Alternative is to go with a Thermal Store, which I know from research can be great but must be set up and maintained properly, plus cost more.
Estimate cost £1000

Install a large solar battery, capable of charging from the grid as well, using off peak electricity (until solar panels are installed in summer, then most charge will come from the panels other than winter). The battery would allow me to access daytime electricity at off peak rate which is important as I have a Everhot Stove 100 (which uses about 80kwh per week).

Est cost £4500


Phase 2 (Hopefully within a year)

Install 2 Solar thermal panels which in theory (if properly set up) will provide 90% of hot water in summer, 25% in winter, avg 50-60% for the year. This would significantly reduce overall need for elec power to heat water in the year, however, less effective in winter.

Est cost £3,500 (DIY plus specialist for prep/final connections)

Install Solar PV Panels & Inverter on large outbuilding south facing roof (space for 18 large panels). Connect up to Solar battery. All spare power can go into battery and water tank (solar coil)

Est cost £3,500 (Do most of the work myself)

Total est cost £12,500

Current costs pa
oil 1800ltrs / 20,000kwh / £1,260

elec 5000kwh / £1,250 (plus 250 SCharge)

total annual £2,510 pa 

12,500 / 2,510 =4.98 years pay back c20% which is excellent in theory.

however, I would still require some off peak power in winter but possibly this can be offset against what can be sold back to the grid? Also I intend to buy an EV soon which would also benefit from the solar pvs and battery if correctly sized.

My concern is if it was this simple then surely most people would go this route. Granted I am able to do quite a lot of the work myself which reduces costs a lot.

Thanks

FreeBear

I'd give Octopus a call and get them to quote for a heat pump.

On a good day, you should get a COP of 4 or more, so a lot more heat out than power in.

Qyburn

FredSomerset said:

however, I would still require some off peak power in winter but possibly this can be offset against what can be sold back to the grid? Also I intend to buy an EV soon which would also benefit from the solar pvs and battery if correctly sized.

I'm hoping our system will do the same, Summer month's exports pay for Winter use. Too early to tell yet as it only went in at the very end of May but so far it's looking promising. We have 20 panels totaling around 8.5kW, 10kWh battery and 6kW inverter. 

Don't underestimate the Summer/Winter difference. We were generating 900-1000 kW in June, July, August vs 56 in December.

Unless you have a ludicrously big battery you're not going to be able to store all of your surplus, our best day exported 55kWh but lots of other days over 30 or 40. So it's important to get a decent export tariff and generally that means having the system installed or at least commissioned by an MCS accredited installer. 

FredSomerset

Thank you for both the replies (anyone else please do add to the discussion).

Heat pump issue is I live in a 1870 cottage. It does have good insulation and double glazing but it is far from a modern well insulated house so generally advice is to avoid heat pumps. Also fitting the pipework around the cottage would be challenging and expensive. Whereas rads and pipework is all in place.

Qyburn - thank you for solar info. Yes I have heard that summer vs winter differential is huge and this is a dilemma. Eco 7 plus battery seems to be the workaround, especially if adding an EV one day.
do you mind me asking which brand/model you went with and approx costs?
thanks.

smallblueplanet

FredSomerset said:

Thank you for both the replies (anyone else please do add to the discussion).

Heat pump issue is I live in a 1870 cottage. It does have good insulation and double glazing but it is far from a modern well insulated house so generally advice is to avoid heat pumps. Also fitting the pipework around the cottage would be challenging and expensive. Whereas rads and pipework is all in place.

Get Octopus to come round and do a quote, that way you'll know for sure. (The deposit is fully refundable)

Petriix

A heat pump can work with your existing radiators and pipes. It's definitely worth getting an opinion before ruling one out, the savings would be huge and the grant is generous. It would work well with your other ideas.

Ectophile

With a system like that, you will end up with more electricity than you know what to do with in the summer, and you'll end up selling most of it to the grid.

Then in winter, when solar is rubbish, you'll have a cripplingly expensive system to run.  A tank of water heated overnight isn't going to be enough to keep the house warm all day.  So you'll be forced to run it on expensive daytime electricity to keep warm.

Look at heat pumps.  They are around 3 to 4 times as efficient as an immersion heater.

FreeBear

Petriix said:

A heat pump can work with your existing radiators and pipes. It's definitely worth getting an opinion before ruling one out, the savings would be huge and the grant is generous. It would work well with your other ideas.

As long as the pipework is not microbore. With a regular mix of 22mm & 15mm pipes, a heat pump should be fine.

This notion that a HP is only suitable for a modern well insulated property is just a myth. As long as it is properly specified and matched with suitably sized radiators, it will keep the place warm.

FredSomerset

Thanks everyone for your feedback : )

Reed_Richards

A 210 litre cylinder will have only a small energy storage capacity.  It's possibly enough to provide hot water for 2 people but if you plan to run you CH off it as well you surely need something much much larger.  @Solarchaser on the Green and Ethical section https://forums.moneysavingexpert.com/discussion/6377030/ditching-gas-going-electric-immersion-only-a-wee-project/p1 does what you are planning to do using only a huge insulated tank in their basement for hot water storage.  I appreciate you will be using batteries for most of your energy storage but I doubt that you have the correct balance between energy stored as heated water and energy stored in batteries.