So now I have a solar PV system how do I make the most of it???

Cardew

nobby1963 wrote: »

Hi All,
Just for info I have today spoken to Immersun direct to ask about their units. They just told me to either call one of their approved installers for supply & fit or one of their distributors for just supply.
I was quoted £450 for supply inc delivery &vat.
My nearest installer had his delivery of the units last week and has so far done one installation and is treating that as a `test` and as such has agreed to call me back in 2-3 weeks time with feedback.
A ball park figure for supply & fit from him was £500 -£600.
We wait to see but my initial reaction at that price for me ( no gas but oil fired heating ) is a definate may be

How much additional 'excess electricity' a year do you think you will save? and the £ savings in oil?

£500 - £600 invested in a long term building society ISA @ 4.5% produces around £25 a year.(compounded)

So estimate of payback time is ?????

Answers on a postcard!

John_Pierpoint

...............and the inflation rate for the pound sterling and the global price of energy is?

Wrong answers available from Gideon & the Governor.

Looks like the "headwind" this winter might have been imposed by those wicked foreigners and God, who don't seem to see the UK as their favourite charity when there are shortages in the food chain.

[Tell me this time next year if I get that wrong].

Hobbo2006

nobby1963 wrote: »

Hi All,
Just for info I have today spoken to Immersun direct to ask about their units. They just told me to either call one of their approved installers for supply & fit or one of their distributors for just supply.
I was quoted £450 for supply inc delivery &vat.
My nearest installer had his delivery of the units last week and has so far done one installation and is treating that as a `test` and as such has agreed to call me back in 2-3 weeks time with feedback.
A ball park figure for supply & fit from him was £500 -£600.
We wait to see but my initial reaction at that price for me ( no gas but oil fired heating ) is a definate may be

Sunny Future Ltd in Aldershot quoted me £420 including VAT and installation. I'm looking to get others in the same street to potentially get a discount.

BPV Solar in Swindon quoted £500 after initially quoting £640 all in.

Hobbo2006

Cardew wrote: »

How much additional 'excess electricity' a year do you think you will save? and the £ savings in oil?

£500 - £600 invested in a long term building society ISA @ 4.5% produces around £25 a year.(compounded)

So estimate of payback time is ?????

Answers on a postcard!

I think a payback period of 3-4 years is a conservative estimate in my case.

We currrently pay around £265pa to heat water via the immersion, as we have warm air gas fired heating. 5-7 kWh's per day is used, depending on number of baths, temparature of the cold water etc. (I used an energy monitor to find this).

If elec pricing rises 3% year on year then in 5 years time we'll be paying £300 just for this.

If the Immersun reduces our electricity use by 50% over the year (should be a conservative estimate based on conversations with 3 of the installers) then this gives the payback estimate quoted.

I think that there is a very good chance that electricity prices will rise faster than 3% and that the immersun will perform better than 50% so I am working by the 3 year payback, based on an installation quote of £420.

Over 5 years I estimate to pay ~£1,400 on water heating without the Immersun.

With Immersun the saving should be ~£700 at a cost of £420

The best 5 year fixed ISA I could find was 4.15% with Halifax which would earn about £100 of interest by the end of the term, based on initial investment of £420.

That's just the money side. Obviously I get a warm fuzzy feeling about doing my bit for the environment. :j

The figures seem to be better in our case so I'm hopoing to include PV fans in our street so that I can get a further discount, which would make these figures even better.

zeupater

Hobbo2006 wrote: »

I think a payback period of 3-4 years is a conservative estimate in my case.

We currrently pay around £265pa to heat water via the immersion, as we have warm air gas fired heating. 5-7 kWh's per day is used, depending on number of baths, temparature of the cold water etc. (I used an energy monitor to find this).

If elec pricing rises 3% year on year then in 5 years time we'll be paying £300 just for this.

If the Immersun reduces our electricity use by 50% over the year (should be a conservative estimate based on conversations with 3 of the installers) then this gives the payback estimate quoted.

I think that there is a very good chance that electricity prices will rise faster than 3% and that the immersun will perform better than 50% so I am working by the 3 year payback, based on an installation quote of £420.

Over 5 years I estimate to pay ~£1,400 on water heating without the Immersun.

With Immersun the saving should be ~£700 at a cost of £420

The best 5 year fixed ISA I could find was 4.15% with Halifax which would earn about £100 of interest by the end of the term, based on initial investment of £420.

That's just the money side. Obviously I get a warm fuzzy feeling about doing my bit for the environment. :j

The figures seem to be better in our case so I'm hopoing to include PV fans in our street so that I can get a further discount, which would make these figures even better.

Hi

I'd take the installers claiming a 50% savings on a £265 immersion electricity consumption with a bit of a pinch of salt ....

I'd go about it by looking at the number of days in the winter when there'd be an excess above background consumption which could be diverted to the immersion, then try to determine how much could likely be diverted .... I'd then look at the number of days in the summer when you would have excess production which would be far in excess of your 5-7 kWh/day of water heating ...

Think logically about it from a total generation POV ... £130 equates to around 1100kWh of electricity consumption (@12p/kWh) which equates to around 30% of the anticipated annual production from a typical 4kWp system .... in the summer, when a 4kWp system is likely averaging 15kWh/day then 30% is possible, in winter, well there will be day's on end when the system achieves absolutely nothing ... to me, that says that 30% of overall generation being diverted to the immersion is questionable, so I'd certainly do some research on the potential supplier's claims before deciding to purchase ...

HTH
Z

Cardew

Hobbo2006 wrote: »

I think a payback period of 3-4 years is a conservative estimate in my case.

Even though you are using 'full' daytime electricity prices of around 12p/kWh, I concur with zeupater that your assumptions are wildly optimistic.

Of course those heating water with gas or electricity will have to cost their savings per kWh at much lower rates - 4p/kWh and 6pkWh with a modern boiler.

Indeed I am surprised that you don't have an Economy 7 tariff and heat your water at around 5p/kWh. On some tariffs the 'break even' percentage for using E7 is below 20% on cheap rate. That 20% can be achieved without any water heating.

Hobbo2006

zeupater wrote: »

Hi

I'd take the installers claiming a 50% savings on a £265 immersion electricity consumption with a bit of a pinch of salt ....

I'd go about it by looking at the number of days in the winter when there'd be an excess above background consumption which could be diverted to the immersion, then try to determine how much could likely be diverted .... I'd then look at the number of days in the summer when you would have excess production which would be far in excess of your 5-7 kWh/day of water heating ...

Think logically about it from a total generation POV ... £130 equates to around 1100kWh of electricity consumption (@12p/kWh) which equates to around 30% of the anticipated annual production from a typical 4kWp system .... in the summer, when a 4kWp system is likely averaging 15kWh/day then 30% is possible, in winter, well there will be day's on end when the system achieves absolutely nothing ... to me, that says that 30% of overall generation being diverted to the immersion is questionable, so I'd certainly do some research on the potential supplier's claims before deciding to purchase ...

HTH
Z

I agree with you in that most of the saving will be in the summer when there's so much excess that we can't use it. The savings in winter will be much smaller. However we bought our panels, along with a wattson monitor back in Feb and even then the wattson was creating graphs where there was space between generation and usage. All of that would get re-directed to the immersion and therefore reduce the load on the imported electricity.

I don't think this product is suitable in many instances but people using electricity to heat water, and also having a 4kWh PV system on the roof seems to give the best results.

Myself and a neighbour are going to take the plunge. If we can get 3 installs in one day for the installer then there would be a discount which brings the cost down and affects the payback. With the unit counting the savings we'd be able to report back to the forum.

zeupater

Cardew wrote: »

Even though you are using 'full' daytime electricity prices of around 12p/kWh, I concur with zeupater that your assumptions are wildly optimistic.

Of course those heating water with gas or electricity will have to cost their savings per kWh at much lower rates - 4p/kWh and 6pkWh with a modern boiler.

Indeed I am surprised that you don't have an Economy 7 tariff and heat your water at around 5p/kWh. On some tariffs the 'break even' percentage for using E7 is below 20% on cheap rate. That 20% can be achieved without any water heating.

Hi Cardew

I factor both the tier1+tier2(if any) savings into our gas savings, so it's over 7p/kWh saving on gas in the summer months on the tariff we're on ....

We've used 12kWh of gas so far this financial year and that was all tagged onto the end of the winter quarter. The remainder has all been solar thermal (ET), therefore no purchase of energy for hot water at all, tier1 or tier2, despite using ~6kWh of H/W per day, therefore with the tier1 threshold being 670kWh/Qtr the saving will all be costed as tier1 (6kWhx92Days=552kWh) ... if totally displacing gas or electricity on a tiered pricing structure allowance must be made for tier1 savings where applicable ...

The advantage of the solar thermal system we have is in the vastly increased storage capacity over a normal H/W cylinder combined with a higher nominal maximum water temperature resulting in being able to cope with a number of consecutive relatively dull days without the need to fallback to importing energy ... In my view it is the lack of a plan to increase the H/W storage capacity which will seriously hinder the ability of the pv energy diversion systems to achieve significant savings as claimed by installers and manufacturers - I suppose that's why they always categorise the potential savings as being 'up to' ... we certainly wouldn't be able to make energy savings anywhere near what we actually achieve without having addressed the total energy storage capacity ...

HTH
Z

Martyn1981

zeupater wrote: »

Hi

Think logically about it from a total generation POV ... £130 equates to around 1100kWh of electricity consumption (@12p/kWh) which equates to around 30% of the anticipated annual production from a typical 4kWp system .... in the summer, when a 4kWp system is likely averaging 15kWh/day then 30% is possible, in winter, well there will be day's on end when the system achieves absolutely nothing ... to me, that says that 30% of overall generation being diverted to the immersion is questionable, so I'd certainly do some research on the potential supplier's claims before deciding to purchase ...

HTH
Z

Hiya Zeup, I've been bouncing those numbers around in my head, since a lot of these companies' claims are more than a little optimistic. However, I'm not convinced that the 1,100 units you suggest is unreasonable. Considering generation from a 4kWp system:

May to Aug should provide 5 to 6 excess units most days. A lot of the days, excess will be higher, but I assume(?) the system and household won't be able to make use of all summer excess. So that's around 600.

Mch, Apr, Sept should provide 2 to 3 a day, with excess days being usable, so that's another 270.

Oct to Feb, conservative estimate of 1 per day, (higher still if the roof has a steep pitch) but again some zero's, but high use of good days, so another 150+. In fact, I'd be willing to bet that over those 5 months you'd see at least 50 days with 3 usable excess units on their own.

So that's around 1,000 units, which I think is a reasonable estimate (not too high or low). Certainly not 'wildly optimistic' as you were misquoted.

I remain concerned at pricing these PV units at nil (rather than 3.2p export), but I suppose it's unlikely we'll see export/smart meters in the next 5 years.

In Hobbo's case (and particular circumstances) I think a suck it and see approach is probably a good bet. But those are particular circumstances that most of us would not gain from.

Mart.

Cardew

zeupater wrote: »

The remainder has all been solar thermal (ET), therefore no purchase of energy for hot water at all, tier1 or tier2, despite using ~6kWh of H/W per day,

The advantage of the solar thermal system we have is in the vastly increased storage capacity over a normal H/W cylinder

HTH
Z

Hi zeupater,

Agree with your 'maths' but the fact that you have solar thermal(and solar PV) makes your situation atypical!

There seems to be an assumption that a HW tank has infinite capacity to absorb 'surplus' electricity, and to ignore the fact that on many days there will be no surplus electricity.

Also with the present metering system, combined with FIT, you still get an assumed 50% export payment regardless of the consumption of your generated electricity.

When smart metering comes in over the next ??years the situation will change and there will be the ability to calculate exactly how much electricity is exported. Every kWh diverted to the immersion heater will reduce the export payment by ??pence. For those with gas CH I suspect the 'savings' will be marginal.

Essentially I am suggesting that the savings from these devices need to be looked at realistically.

EDIT - hadn't read Martyn's post above re smart metering - with which I concur!