ASHP - current going rates?

chamelion

JKenH said:

I am confused. The Mitsubishi Ecodan 8.5 heat pump mentioned in the original post is air to water so is likely to be RHI eligible. 

Is the OP looking to heat the whole property with this unit? That is what it appears to be designed for using radiators, I.e. an alternative to a central heating system powered by a gas boiler.

Or is the OP looking for an air to air split unit to locally heat one room with an aircon style unit mounted on the wall and an outside heat exchanger just connected to the one internal unit? It is also possible to get one outside unit to drive several indoor units (multi split) but that is not what the Mitsubishi Ecodan 8.5 heat pump is designed for (as far as I am aware).

Hey - so yes, it's the latter. And you're right, the ecodan is air to water, clearly i'm the one who was a complete idiot here I think i was combining multiple things i was finding into a single system but they were entirely different things...

silverwhistle

These threads are definitely educational for all of us! ;-)   But it does set me thinking how the move to more heat pumps is going to go with the general level of knowledge of policy makers, installers and customers. I have to admit personally not having much of a clue. It's another market where the ex-double glazing sales people will move in...

Martyn1981

chamelion said:
Hey - so yes, it's the latter. And you're right, the ecodan is air to water, clearly i'm the one who was a complete idiot here I think i was combining multiple things i was finding into a single system but they were entirely different things...

Don't worry, as you set me off on yet another tangent, and perhaps another possibility for many of us:-

So, whilst air-air isn't supported by the RHI, it is much cheaper, so I was pondering what impact on my gas consumption another one or two A/C units might have, and the corresponding costs/savings on other proposals spinning around in my head.

So, let's say I install another 5kW multi-split unit, or perhaps 2x 2.5/3.5kW units (around £2k installed), but then I run them all day and night? Next what if I move to an E7 tariff, then the cost at night for the heat will be at or below gas prices. Then I add the 1.6kWp steep south facing PV I've been planning (on hold whilst I research DNO V2G options), that should add around 1kW of generation to current gen, powering most of the additional daytime needs of said ASHP.

Additional benefits (for me) would be the £5k+ savings on a domestic battery, since (1) any spare cold month gen will get used as heating, (2) summer excess can get used to charge BEV(s), and (3) E7 rate in the summer would be close to the cost of operating the battery. Could even consider downgrading to a smaller boiler, and non combi with a HW tank and diversionary switch.

Perhaps an odd hybrid setup, but an interesting package, perhaps? Haven't really thought it through, but with gas consumption of ~7MWh pa (heating, cooking (oven only) and DHW), it might be doable with 2MWh of ASHP consumption.

ASavvyBuyer

Hi Mart,

Unfortunately, when I inquired if planning permission was needed for a second ASHP, the answer was yes (in Wales), at a cost of about £200.

However, the savings in ££'s & CO2, are still making me think it would be worthwhile to install another in the kitchen and let the warm air circulate the rest of the bungalow from the 2 units.

As we are on the Octopus GO Faster trial, of 5 hours @ 5.5p/kWh, we find it is worth leaving the existing ASHP on overnight on a low setting, with the internal doors open to allow the flow of warm air.

Coastalwatch

If it's of any assistance we had two 2kW ASHP systems installed in November 2018. The first winter we used them for heating during daytime hours when energy from solar was available. This winter we've not used gas for heating at all and are surviivng very comfortably with sole use of the ASHP's through day time and evenings. I know it's been a mild winter but we've kept temperatures around 18 during daytime hours and at 22 in the lounge and bathroom early morning and evenings. Monthly combined consumption figures for ashp's from October in kWh's being -115, 210, 288 & 266. Don't know if these help to shed some light on matters.

chamelion

Coastalwatch said:

If it's of any assistance we had two 2kW ASHP systems installed in November 2018. The first winter we used them for heating during daytime hours when energy from solar was available. This winter we've not used gas for heating at all and are surviivng very comfortably with sole use of the ASHP's through day time and evenings. I know it's been a mild winter but we've kept temperatures around 18 during daytime hours and at 22 in the lounge and bathroom early morning and evenings. Monthly combined consumption figures for ashp's from October in kWh's being -115, 210, 288 & 266. Don't know if these help to shed some light on matters.

This is really useful. So if you use 250kwh/month as a typical baseline, that's 8.33kwh/day. 
On my octopus agile tariff that'd be about 50-55p/day of electricity. not bad! 
Although, gas wise I may use 15-20kwh per day for heating, at 2.5p/kwh that works out about the same... 
Only benefit for me would be that the ashp system's daily running cost would be somewhat offset by the PV i generate - and would keep the house warm (18-22 degrees) through the day, rather than just during the times we're home (although, that wouldn't really benefit us...) 

Coastalwatch

For further consideration we live in a two bed bungalow of approx 100 sq meters which the ashp's heat quite well by opening or closing doors accordingly. Depending on your property and it's layout two might not be sufficient. For instance the one in our lobby, which has four doors serving the two beds, bathroom and entrance hall heat all these in varying degrees. The bathroom can be kept toasty with the others kept at lower temps. The second ashp serves the lounge/diner 28 sq meters with some deflected into the hall, or not, as required.

Hot water is taken care of by a 210litre thermal store heated by a 3kW immersion element. I've no meter on this but around 5kWh/day would be a good estimate. It's not on permanently, but mostly when the sun is shining. Now we're out of the darkest days of winter, solar will gradually offset more of our consumption as the weeks progress. Our total monthly consumption from Oct being 199, 481, 552 & 671 kWh's. These include the charging of our EV which consumed a total of 471 kWh's from the grid for the four month period.

Good luck with your deliberations. Good fun, isn't it!

Martyn1981

Coastalwatch said:

Good luck with your deliberations. Good fun, isn't it!

Yep, great fun indeed. For me, it's the way the package of ideas and solutions all integrate. E7 didn't work for us as our leccy consumption is relatively low, but with a BEV it now does. Then E7 makes night time use of ASHP's much cheaper, and whilst E7 increases day rates, PV reduces daytime consumption, so all the parts are making for an every better whole.

The one downside is that I was really looking forward to getting a domestic battery, but displacing nighttime units at E7 rates doesn't make sense, and the cost would probably cover the two additional A/C units, extra PV and even a new smaller boiler, as ours is 20+yrs old. But that's why I enjoy a good ponder on here, and times are certainly changing fast at the moment, so my plans need to adapt accordingly.

michaels

Food for thought, I am hoping on the ovo v2g trial soon - this means 2 years of expensive flat rate leccy but after that a v2h (or possibly v2g) system that could be used in conjunction with a time of day tariff and the pv to do some 'clever stuff' including ideas like adding air to air hp to our heating mix along with the gch/hw, perhaps replacing gas with electricity space heating only when it makes economic sense....

Solarchaser

Quick question for those experienced in all things ashp. 
I have a car port, with a 1st floor extension above, would the carport make a good home for ashp, as it's out of the sun, Or is it better south facing to catch sun?