Posted By: skyewrightI'm sure it can be very cold in Canadian winters, but what's the RH% like? I presume there is less icing up (& thus defrosting) with drier air?

Once it's below freezing, it's pretty dry out East where I am, but in the west coast climate, it's more like the UK, with much higher humidity (but higher temperatures too). One of the reports listed above takes into account the defrost cycles.

Paul in Montreal.

Posted By: SteamyTeaIsn't it more policy and legislation lead.

Exactly . ( I'd not even call it offsetting)
I think it's a real concern (in UK with our low renewable % mix ) that if people move from gas to electric as their main space heating energy source , new renewable entering the grid will be dwarfed by this increase, Fossil fuels will be used to fill this increase in demand at peak times ( gas stations at 60% (40%?) efficiency probably) the end result will be a reduction in the overall renewable % mix of total demand and more pollution.

do you really think we'll get anywhere near those targets ? I dont

Posted By: jamesingramdo you really think we'll get anywhere near those targets ? I dont

Me neither. Ridiculous targets.

Posted By: Seret

Posted By: jamesingramdo you really think we'll get anywhere near those targets ? I dont

Me neither. Ridiculous targets.

This is my concern , unrealistic targets,
Most housing is existing and will not ever reach standards of energy efficiency discuss on this forum. Moving to electric heating with the expectation of demand reduction through mass low energy housing and high renewable grid content, seems a bit premature and probably pie in the sky to me. Government are incentivising ASHP etc. far to soon , sort the grid and energy demand out first, then look at heat sources to suit what's required and available . Anyway, I think , give it a couple of years and this shale gas will tilt the scales again.

I believe by far the biggest UK producer and hence supplier of renewable electricity is SSE, they do gas .
(8.2% increase, you say , perhaps I will change to Co-op.)
Of the 'sound' suppliers , not sure if ecotricity do gas ?
Can I refer to these 'green' supplier as 'sound' (ethicial) supplier as I believe they are better than the usual lot, even if I'm not convince they actually affect the development of new renewable generation greatly, other than in a lobbying , zeitgeisty kind of way.

Posted By: jamesingramI believe by far the biggest UK producer and hence supplier of 'green' (renewable) electricity is SSE, they do gas .

Quite possibly, 14% of their fuel mix. Unfortunately overall they use loads of coal, and very little nuclear, so their mix ends up being one of the most carbon intensive. Only Scottish Power is dirtier.

Posted By: jamesingram
I think scale needs to be considered. Though I'm a fan of these 'sound' suppliers , ecotricity , good energy etc. It's the big players that have the potential to make the difference due to their large share of the generation capacity and it's government/EU, targets/incentives/fines that'll force/encourage them to invest in new renewable generation capacity.

Absolutely. All those vast wind farms off the coast aren't owned by the minnows. But as an itty bitty consumer voting with your wallet is about all you can do. Buying even a "green" tariff from the big boys will make even less difference than from a proper green supplier, as that'll just be their existing renewables obligation packaged up and sold as if it's not something they'd be doing anyway.

Good energy , Ecotricity do have thier own generation which they've invested in , but another concern I have is that even if this is outside the existing renewables obligation that generator are suppose to comply with , ie over and above the amount of new renewable generation that should be entering the grid each year due to legislation (wont they have to comply like all othes ? ), surely the big boys are in the same position you rightly suggest , but vie a versa , they can buy the ROCs off smaller 'green' generator and do less themselves ?

Though Ecotricity will purchase green energy from alternative suppliers, unlike other generation companies they promise to devote their investment purely to building additional renewable generation capacity, so I assume it will have a (lumpy) impact at the margin (or, given they're small, the margin of the margin)?

I think the popularity of these companies is more important as a signal to policy makers and brown generators. If it's growing rapidly (and I don't know the figures), then MPs and brown generators may devote more resources to greening policy or themselves.

Back to my original question (are A2A heat pumps a sensible way for natural gas heated homes to knock a chunk off their carbon emissions?) thanks for the info Paul, very helpful. Skyewright has of course raised the point that temperature is perhaps not the main problem here. Even in Edinburgh, the lowest average daily minimum temperature, in December, is still +1.3 degrees C. We get much lower than that only very rarely. But we get a ton of rain around this temperature, so UK A2A pumps probably spend a lot more time defrosting than in, e.g. Canada, Japan (and probably even Sweden Chris?) I've just finished reading an article on the BBC about the 'uniqueness' of UK weather, given it's position. Although collating international data will be useful, it probably mostly builds the case for a UK specific study of these things I suppose.

Any other observations on the sense, or otherwise, of my 'low subsidy' proposition?

There are only two viable renewable alternatives for electrical generation at the moment, near shore and onshore wind. PV can make a difference, but still too expensive at the moment.
If you wanted to make a difference with your cash would you not be better off helping the developers of wind farms fight the anti-wind brigade.
I am not sure if there is a way to do this, other than send cash to RenewableUK and suggest that they put up several cross party candidates at local elections.
Controversial approach I know, but no more controversial than any other politics. Makes me wonder what the 'Green' party is all about.

The alternative is that we pay a higher price, which I am not against as energy is pretty cheap.
100 grams of Red Lentils costs about 22p and has 0.12 kWh of energy when cooked.
So about £1.83/kWh and probably takes a kWh to cook at £0.18/kWh.

Posted By: jamesingramTo get back to my main points relative to the topic here is.

+1 Buy that man a Stella!

Posted By: jamesingramTo get back to my main points relative to the topic here is.
2. If people switch to electric space heating before the grid has reached a certain level of renewable input.
the new renewable generation entering the grid each year might not be able to keep up with this demand switch from gas to electric and the percentage of renewable to demand might even drop . Creating more potential pollution.

Not if the electricity is used to heat space more greenly than using gas directly? i.e. if the gas that would have been used directly for space heating is instead burnt in a power station (i.e. incremental electricity is not met by renewables, but existing fossil fuels), but the electricity produced drives heat pumps with COPs higher than 2.4 (not 2.2 as I mentioned earlier - oops!), then there's a net carbon benefit even without more renewables isn't there? If the SPF manages 3.6, maybe reasonable for new systems, that would be a 33% reduction in carbon intensity, which sounds worthwhile to me.

Posted By: djh

Posted By: GarethCBack to my original question (are A2A heat pumps a sensible way for natural gas heated homes to knock a chunk off their carbon emissions?)

If your space heating is four times the size of your DHW demand, then the best thing to do is insulate your house and reduce demand! Once you've reduced space heating to a similar value to DHW, the sums will look different.

Three times (to split a hair!). I've a solid wall period property with massive cornicing througout and similar flats above and below (sliced up villa). I've looked into SWI and the viable options (those that don't kill my cornices) seem to cost a fortune, and I'm worried about what I'd do to air flow around the overall property. In a conservation area so would have to replace my sash and case windows with like for like timber (ouch). Even replacing the single glazed sashes with double glazed units is painful. I'm stuck to being anal about draught proofing.

That does of course make me a special case. Might knock my argument that there are loads of gas-heated properties for whom A2A is the best option (if most of the rest can be insulated effectively and cheapishly).

Posted By: jamesingramwhere do you think Good energy etc. get the vast amount of there renewable energy they sell from ? I believe it's off the trading floor from the likes of SSE.

There's a little detail (but no numbers) on their policy on their website:

http://www.goodenergy.co.uk/about/a-different-kind-of-energy-company/how-we-buy-and-sell-electricity
http://www.goodenergy.co.uk/media/BAhbBlsHOgZmSSIdNTFlZmEzMDUwODdjOWMwMDAyMDBjZTkzBjoGRVQ/ge_procurement_policy_WEB_110912.pdf

They state they have contracts with 500 renewable suppliers, and that buying from the National Grid is their last resort position. Over a year they have to have bought enough power from renewable sources to cover all their users' consumption. They don't simply buy whatever is going.

To again bring it back to topic, how does A2A stack up to A2W assuming that it is only being used to deliver heat (no DHW - I think we all accept that higher DHW temps reduce CoP of heat pumps) If A2A is delivering heat into the home by heating air to 30C and an A2W is delivering heat to UFH or low temp radiators at 30C what would be the difference in efficiency between them if any? Lets assume for the sake of argument, both have the same size compressor and same type of refrigerant. From an uneducated point of view you are extracting heat from the same source (ambient), running it through the heat pump before using the output to heat either air or water.