energy help required

thompsonguy · 18 April 2019 at 11:41PM

hi
i own a large Yorkshire stone house quite well insulated with 4kw solar system on my roof

i have quite a new boiler and ample radiators however 10 months of the year i need to keep the heating on constantly due to my partners health being on blood thinners which results in very big gas bills obviously in a normal situation setting the timer/ stat would be the cheapest way of keeping my house warm however our situation is far from that

my thoughts is to put in a Tesla power wall in so using economy 7 to charge the batteries at night as well as the solar panels during the day

then either get carbon glass panels for each room (that have the health benefits as well) or getting a Mitsubishi ecodan 11.2kw air to heat pump i just dont know which one

glass panels would cost around £4500 for all my house and can be controlled individually

air to heat would cost around £11000 with about £8000 coming back with heat incentive

any help would be great

[Deleted User] · 19 April 2019 at 9:39AM

Probably best to post this in the Green and Ethical forum where the solar people hang out https://forums.moneysavingexpert.com/forumdisplay.php?f=100

nigelbb · 19 April 2019 at 11:49AM

No form of heating using paid for electricity is ever going to be as cheap as heating with gas whether it's Economy 7 or a heat pump. Electricity is 4-5x the cost per kWh compared to gas.

A Tesla powerwall would be spectacularly uneconomic to charge up with Economy 7 even assuming you were saving 10p/kWh. A 14kWh power wall costs getting on for £8000 installed so assuming that you could save £1.40 per day would take over 15 years to pay for itself & even then would be more expensive than 14kWh/day of gas.

If you are heating with gas & the house is well insulated then if you want to reduce your energy bills the only way this is possible is wrap up well use fewer rooms & acclimatise to lower temperatures.

matelodave · 19 April 2019 at 7:17PM

You'd need to do some very careful and detailed sums to work out whether giving up mains gas for electricity would be worthwhile.

Even a heat pump doesn't work out as cheap to run as mains gas. If you are heating for most of the day and evenings rather than at night then they dont work everso well with E7. Neither do they really suit solar panels as you need heat in the winter when the sun doesn't shine, the days are short and they are working their hardest.

I don't know about trying to run it from a Tesla Powerwall, but my 11kwh Daikin ASHP can chew it's way through 45-60kwh a day when it's everso cold so you'd have to be convinced that you could store enough energy and that the powerwall could cope with the starting current when the compressor and fans are running.

You'd also need to ensure that your heating system was suitable to run an ASHP - you may find that the plumbing and radiators are undersized to take advantage of the lower water flow temperatures - running them at higher temperatures will significantly reduce their efficiency and increase running costs - most people who just bung one onto an existing heating system are bitterly disappointed with the performance and running costs.

You only get RHI for Air to Water heatpumps, not Air to Air and you need to make sure that the system is installed by an MCS approved installer. RHI is based on your EPC requirements and may not be as much as you expect, so make sure you get the calculations correct.

jk0 · 19 April 2019 at 7:36PM

Years ago I did the sums for nicad batteries. I worked out that the batteries would fail long before I had paid off their cost in tariff shift savings.

I suspect it would be the same for Tesla batteries.

energy help required

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