Choice of intelligent switches ?

zeupater

Cardew wrote: »

Hi,

Agree, but your situation, and ultra low gas consumption, which justifies using Tier 1 rates is atypical.

In any case virtually every company is stopping the Tier1/Tier2 tariff and having a daily standing charge; so 4p/kWh for gas would be a ballpark figure.

Hi

Maybe, maybe not .... if a system is displacing the use of gas which is tier priced and the gas consumption within the summer months is below, or even close to the tariff threshold, then the tier1 tariff is the appropriate figure to use .... my ultra-low winter gas usage really plays no part in the calculation seeing that the period of consideration only accounted for the ~180day summer period. As long as the volume of water in the HW cylinder is large enough to withstand a couple of days of low/no sunshine and both the house and cylinder are well insulated, then there should really be no need to use a significant amount of gas based secondary water heating during the summer ...

It's not just based on logic, it's based on over 30 years of direct experience for ourselves and other family members .... it's been cloudy today and the solar thermal system has only managed to warm the cold water at bottom of the cylinder, yet the HW supply from the top of the cylinder is still ~67C, so no gas today, again ....

HTH
Z

Martyn1981

Thought I'd revisit these numbers, now that the Solarimmersion is getting popular, and is a bit cheaper than the Immersun:-

Martyn1981 wrote: »

What an oddly selective comment (my bold)!

Just checked my last two sunny quarters (2008, nah, I'm jesting) Apr-June and July-Sept.

We used approx 1200kWh, and 450kWh respectively (heating, water and gas oven (not hob)). Apr to June was exceptional this year, as we used intermittent heating through to mid May, whereas normally heating goes off late Mch/early Apr.

Checking price deals on-line the two cheapest companies were NPower with a tier 1 qtr of 1143kWh, and Scottish Power with a tier 1 qtr of 670. (Npower cheaper due to discounts) So in a normal year all savings would be at tier 1 prices.

Given that probably 75% or more 'diversion' will take place during those months, and using some actual, and some guessed diversion, I get:

Winter months 250 / 75% efficiency * 3.948p = £13.16
Summer months 750 / 75% * 7.642p = £76.42
Total = £89.58

Clearly each households circumstances will differ.

Mart.

I reckon 1,000kWh's of PV diversion is possible for anyone with a system of 2kWp or larger, but perhaps, more reasonable for systems of 2.5kWp and up.

Looking at Ebico prices, which are all in, so have no standing charge, but a slightly higher gas price, I find 5.06p/kWh:-

https://www.ebico.org.uk/products-and-prices/our-gas-prices

So after boiler losses and waste heat (pipes etc), I'd guess a unit of leccy displaces about 6.5p of gas(???).

So 1,000kWh's of leccy = £65pa.

But only till smart meters arrive. Oh, and also assuming that 750kWh's of diversion in summer is possible - that's about 4.2kWh's per day on average, but solar isn't exactly average!

Mart.

zeupater

Martyn1981 wrote: »

Thought I'd revisit these numbers, now that the Solarimmersion is getting popular, and is a bit cheaper than the Immersun:-



I reckon 1,000kWh's of PV diversion is possible for anyone with a system of 2kWp or larger, but perhaps, more reasonable for systems of 2.5kWp and up.

Looking at Ebico prices, which are all in, so have no standing charge, but a slightly higher gas price, I find 5.06p/kWh:-

https://www.ebico.org.uk/products-and-prices/our-gas-prices

So after boiler losses and waste heat (pipes etc), I'd guess a unit of leccy displaces about 6.5p of gas(???).

So 1,000kWh's of leccy = £65pa.

But only till smart meters arrive. Oh, and also assuming that 750kWh's of diversion in summer is possible - that's about 4.2kWh's per day on average, but solar isn't exactly average!

Mart.

Hi

Changing gas supplier could save us a few pounds/year then .... I'll be looking at energy prices in the next couple of months anyway ....

Regarding the 4.2/4.7kWh/day from the intermittent source (solar), whether diverted pv or thermal ... that's where the larger HW cylinder capacity comes in handy, especially in Spring/Autumn ...

HTH
Z

Martyn1981

zeupater wrote: »

Hi

Changing gas supplier could save us a few pounds/year then .... I'll be looking at energy prices in the next couple of months anyway ....

HTH
Z

Just a word of warning if you are looking at the Ebico leccy prices. The north of Scotland has the highest tariff, which is also shared by anyone living in the sea, or on any of the white lines that divide the regions - I kid you not.

(I notice the strangest stuff!)

Mart.

spgsc531

Martyn1981 wrote: »

Just a word of warning if you are looking at the Ebico leccy prices. The north of Scotland has the highest tariff, which is also shared by anyone living in the sea, or on any of the white lines that divide the regions - I kid you not.

(I notice the strangest stuff!)

Mart.

Sure you're not sniffing them for that effect?

Cardew

Martyn1981 wrote: »

Looking at Ebico prices, which are all in, so have no standing charge, but a slightly higher gas price, I find 5.06p/kWh:-

https://www.ebico.org.uk/products-and-prices/our-gas-prices

So after boiler losses and waste heat (pipes etc), I'd guess a unit of leccy displaces about 6.5p of gas(???).

So 1,000kWh's of leccy = £65pa.

The figure of 6.5p/kWh for Ebico gas is reasonable for a fairly inefficient boiler.

However Ebico is more expensive for people, unless they have very low gas/electricity consumption.

The average UK gas customer uses 16,500kWh. Checking my area(Midlands) for that consumption, Ebico costs £131 more than the cheapest tariff(£833 - £702)

In fact the cost is even more as getting electricity from a different supplier means you lose the dual fuel discount. Ebico electricity is also very expensive unless you have very low consumption.

Therefore it wouldn't make financial sense for most people to get Ebico gas in order to be able to use a figure of 6.5p/kWh in calculating savings per 1000kWh.

Of the cheapest tariffs available, there are several from the 'Big 6' where gas is still under 4p/kWh.(the lowest of those I looked at was 3.53p/kWh)

Martyn1981

Cardew wrote: »

The figure of 6.5p/kWh for Ebico gas is reasonable for a fairly inefficient boiler.

I thought it was a reasonable figure to use, as I simply copied your calculation from post#277 and rounded off. If you prefer, it's actually 5.06p / 0.8 = 6.325p

Cardew wrote: »

However Ebico is more expensive for people, unless they have very low gas/electricity consumption.

The average UK gas customer uses 16,500kWh. Checking my area(Midlands) for that consumption, Ebico costs £131 more than the cheapest tariff(£833 - £702)

In fact the cost is even more as getting electricity from a different supplier means you lose the dual fuel discount. Ebico electricity is also very expensive unless you have very low consumption.

Therefore it wouldn't make financial sense for most people to get Ebico gas in order to be able to use a figure of 6.5p/kWh in calculating savings per 1000kWh.

Of the cheapest tariffs available, there are several from the 'Big 6' where gas is still under 4p/kWh.(the lowest of those I looked at was 3.53p/kWh)

Have a think about that again - you say that the Ebico figures only really work for those people with lower electricity and lower gas consumption. Yes I agree.

Now consider the 'context'. People with PV, looking to lower their gas consumption (or for others - E7, lpg, oil etc).

So, to repeat what I said last year, and re-posted yesterday, "Clearly each households circumstances will differ."

For those people comparing prices pre-PV or pre-intelligent switch, if they have two options with similar annual totals, they should probably choose the tariff with the highest unit cost and lowest (even zero) standing charge, as this will bring the greater savings when demand is reduced.

Furthermore - whilst leccy consumption is probably more stable and predictable - when considering gas consumption, they should probably look to higher usage years as a baseline, to avoid higher bills impacted by that higher unit cost.

Mart.

OffGridLiving

Martyn1981 wrote: »

Now consider the 'context'. People with PV, looking to lower their gas consumption (or for others - E7, lpg, oil etc).

Would there be sufficient power generated from PV in winter (at the height of gas useage) to lower gas consumption? Especially given that the immersun type devices direct excess energy to the HW tank that's not being used elsewhere by fridges, freezers and the like?

Cardew

Martyn1981 wrote: »

Have a think about that again - you say that the Ebico figures only really work for those people with lower electricity and lower gas consumption. Yes I agree.

.

I have! and IMO my reasoning is correct.

1. I was merely querying the claim that a 3kWp system with the device would save £80 pa off the gas bill.

2. Virtually all tariffs now are Daily Standing Charge and thus gas unit prices are in the region of 4p/kwh.

3. Ebico would work out better if you have seriously low gas consumption. However it would be pointless getting Ebico even if you only used 50% of the UK average gas/electricity consumption. Someone with average gas consumption(in my area would pay £131 pa more with Ebico than the cheapest tariff which would more than wipe out any savings from using solar electricity to save gas.

4. Please note the context! I was querying the figures in one post and having a discussion with zeupater.

Martyn1981

OffGridLiving wrote: »

Would there be sufficient power generated from PV in winter (at the height of gas useage) to lower gas consumption? Especially given that the immersun type devices direct excess energy to the HW tank that's not being used elsewhere by fridges, freezers and the like?

Hiya, from what I've read on here, and elsewhere, I don't think such devices will have much of an effect at all on gas consumption during the winter. So really you'd be looking to the warmer 6 months (can we describe them as BST months for simplicity?)

Reading some comments recently, I came across this line; "In the last week of April when we were doing at least 10kWh per day on the solar, the gas boiler didn't come on at all to heat the hot water. There were a few afternoons that week when the ImmerSUN will stop diverting as it says the hot water tank is "hot".

Also, presumably, available diversion will grow disproportionately to generation (until the tank is hot), eg. If generation is 8kWh's and consumption is 6kWh's, then available excess is 2kWh's. But if generation doubles to 16kWh's and consumption stays at 6kWh's, then available excess is 10kWh's a five-fold increase.

So I'd have thought the benefits of these devices are primarily BST based (rather than GMT), as per my comments last December.

Mart.