Energy Saving Trust Q&A Centre

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Energy_Saving_Trust_company_representative

dc1606 wrote: »

We have been offered C rated windows of 1.6U or A rated windows of 1.4U for c.£300 more (10 windows). Is it worth it? Would we notice the difference?
how much might the extra saving be - assuming all windows closed?
How are U values related to the A-G ratings?
Thanks.

Hello there
I've been trawling through the forum looking for unanswered questions, and I think yours might be one. If that's the case, then I'm very sorry. I appreciate your request may be out of date now as you've probably made your choice, but here is an answer anyway in case it helps you or anyone else:

For a typical 3-bed gas heated semi, the likely additional saving in annual gas use from choosing A-rated windows over C-rated is about 235 kilowatt hours per year. At current gas prices that is worth about £9 per year.

If you assume your windows will last 20 years that gives a lifetime saving of £180, making the more expensive windows not worth it in pure cash terms. But if you expect gas prices to rise significantly over the next 20 years, as most people do, then the more expensive option could be worth it in the long term.

If you have a more expensive heating fuel such as electricity or oil, then the A-rate windows are likely to pay for themselves even at today's fuel prices.

As for the relationship between U-value and window rating, it's not that simple. The window rating is based on an index calculated from the U-value of the window (including frame), the air tightness of the window, and the amount of solar energy that the window lets into the room. So the window rating should give a more accurate indication of the total energy impact of different windows than a simple comparison of U-values.

izmark

Hi there,
This question is certain to have been posted elsewhere, but I'm not sure where to look.
Anyway, is it more efficient and/or cheaper, to keep the heating on all the time i.e. controlled by the thermostat (which is in the hall), or should it be controlled by the timer and come on and off at set times?

Cardew

izmark wrote: »

Hi there,
This question is certain to have been posted elsewhere, but I'm not sure where to look.
Anyway, is it more efficient and/or cheaper, to keep the heating on all the time i.e. controlled by the thermostat (which is in the hall), or should it be controlled by the timer and come on and off at set times?

Covered many times in the gas and electricity forum.


This is a quote from the Energy Saving Trust faq

Question
Is it more economical to leave my heating on 24hrs in the winter?

Answer
No. It is a common misconception that it is cheaper to leave your hot water and heating on all the time. Boilers use more power initially to heat water from cold, however the cost of this is greatly exceeded by the cost of keeping the boiler running all of the time.

The best solution is to programme your heating system so that it comes on when you need it most (possibly early morning and in the evening), and goes off when you don't need it (when you are out of the house or asleep). There are a range of controls that can be used and your heating engineer will be able to provide you with the most appropriate solution.

Depending on your circumstances it may be necessary to keep the heating on all day during winter but it will cost more than if you turn the heating off when you don't need it.

Energy_Saving_Trust_company_representative

Cardew wrote: »

Chest puffed out with pride;)

P.S. Do you know when the results of the extended trial are to be published?

We currently expect the second stage of the heat pump field trials to be published in summer 2012.

cultsmill

I like many others installed an ASHP on the premiss that the technology would be covered under RHI or what ever the government is calling it this month. That was back in November 2010, since then the Government has removed ASHP from the available technologies, made a statement that a grant of £80 would be payable to cover the period to October 2011 when the actual scheme would be introduced, now state that any installation commissioned before July 2011 is not elligible.
Have I got this completly wrong or have I been looking at the wrong application paperwork.

It cost me £16,000 to install the ASHP and uses more electricity than you can throw a stick at.

Cardew

cultsmill wrote: »

It cost me £16,000 to install the ASHP and uses more electricity than you can throw a stick at.

Care to elaborate and give some figures please!

Gizmosmum_2

cultsmill wrote: »

It cost me £16,000 to install the ASHP and uses more electricity than you can throw a stick at.

That seems like a lot to pay! We trialled ashp's in some rural well insulated houses in 2005 as part of EST's innovation funding - although not as comprehensive as EST's analysis it was clear then that the COP stated was highly unlikely to be achieved and the best we could get was a relatively favourable comparison with storage heaters because at least you could control the heat when you wanted it.

Loads of ashp's now provide backup to compensate for their inability to provide sufficient heating - they cost an arm and leg to run because most of the heat is generated on cold days (when ashp are particularly inefficient) by using peak rate electricity to fuel the back up electric heating included in the boiler.

I hope that makes sense??? It sounds as though that's what you have had installed.

Energy_Saving_Trust_company_representative

cultsmill wrote: »

I like many others installed an ASHP on the premiss that the technology would be covered under RHI or what ever the government is calling it this month. That was back in November 2010, since then the Government has removed ASHP from the available technologies, made a statement that a grant of £80 would be payable to cover the period to October 2011 when the actual scheme would be introduced, now state that any installation commissioned before July 2011 is not elligible.
Have I got this completly wrong or have I been looking at the wrong application paperwork.

It cost me £16,000 to install the ASHP and uses more electricity than you can throw a stick at.

I think you have been looking at the wrong schemes to some extent, but it is confusing, so here is my summary:

Domestic Air Source Heat Pumps that were installed on or after 19th July 2009 may well be eligible for support under the RHI (Renewable Heat Incentive) from October 2012, but we do not yet know the eligiblity criteria or the tariffs. So it is not certain that you will get support, or how much you would get, but you have not yet been ruled out.

The Renewable Heat Premium Payment (RHPP) is a separate scheme that started on the 1st August 2011. This pays a lump sum to new eligible installations. You are not eligible for this because you installed before July 2011. However, this is a single payment (£850 for an ASHP) rather than the ongoing payment that the RHI should offer, so it is a much smaller incentive.

There is a non-domestic RHI starting this year, and this will not support ASHPs in year one. This is probably the source of the idea that ASHPs will not be supported, but it does not apply to domestic installations. Support of ASHPs for non domestic customers in future years is under consideration.

Regarding the running costs of your heat pump, they do use a significant amount of electricity to run, and electricity does cost more than other forms of energy. So whether they are worth it depends on your circumstances. In our field trials, a typical ASHP achieved a total average system efficiency of around 220% - that is it would produce 2.2 times as much useful heat as it used as electricity. A brand new gas central heating system will achieve around 86%.

At current prices this makes the heat pump more expensive to run than the gas system. However, the best ASHP installations achieved an average more like 300%, making them cheaper to run than the best gas systems. And even the typical installations are generally cheaper than oil heating, and definitely cheaper than any form of electric heating. Even these savings will take a long time to pay off a capital cost of £16,000, but when the RHI kicks in (assuming you are eligible) then the payback period should come down dramatically.

If you are concerned that your system is not running at optimum efficiency, there are some things you can do:

1) Set the controls so that they run for longer periods at lower temperature. Heat pumps are more efficient when running at lower temperature, but they are also more efficient when they aren't stopping and starting all the time, so you get a double benefit from this change in control.

2) Improve your insulation and draughtproofing. Apart from saving you energy in the first place, this makes it easier to adopt option (1) without getting cold, making your heat pump more efficient again. So you get a double, double benefit.

grahamc2003

Energy_Saving_Trust_company_representative wrote: »

The Renewable Heat Premium Payment (RHPP) is a separate scheme that started on the 1st August 2011. This pays a lump sum to new eligible installations. You are not eligible for this because you installed before July 2011. However, this is a single payment (£850 for an ASHP) rather than the ongoing payment that the RHI should offer, so it is a much smaller incentive.
.

I've read this sort of statement several times in various places, and it's very confusing, and probably incorrect or at best incomplete.

There are other qualifying criteria which it's best to mention in such a statement to avoid confusion. After quite a bit of hunting around and approaches to heat pump installers, some of the main criteria are the type of ashp for which the rhpp applies. It doesn't apply for instance to air to air heatpumps, or exhaust air heatpumps - confusing since I think I'm correct in saying the rhi may apply to those technologies when the decision is made (could you confirm that please?)