Free solar panel discussion

Elainemary

grahamc2003 wrote: »

Hello Elaine, Could you explain in more detail why you think re-wiring an economy seven installation would be beneficial in some way? Also, could you expand on why, if you have e7, running high powered items like washing machines (presumably at midday instead of at night) is somehow beneficial if for those who have 3kW (capacity) of free solar panels?

I must say, I agree with others who think the idea is completely counterproductive - in that it will not only cost more (substantially more if the heating moves to day rates), and also lead to higher co2 emissions (even though some of the energy comes from the solar panels)

I don't want to rewire the economy 7 and you've missed my point which was that it was a good idea to KEEP THE REST OF US INFORMED as to progress with the company. Sorry if I was unclear.

Elainemary

Jenmaljal wrote: »

I have applied to Homesun for free solar panels. I have a bungalow that faces due south and has masses of roof space with no trees or building shading the roof. However Homesun require 30 sq metres of roof space facing due south - having worked this out I reckon this must be the size of a factory, manor house, school or in any case a very large building, not your normal house owner. So no free solar panels!

Hi there and welcome to the club!! Glad I'm not alone with Homesun and their " must have's ".

energysavingexp

Elainemary wrote: »

Hi there and welcome to the club!! Glad I'm not alone with Homesun and their " must have's ".

30 sq mtr is only the size of an average houes.
roof size 20 ft high x 15ft wide

K4blades

zeupater wrote: »

Hi All

Following on from grahamc2003's post and the one referenced above (Which has been removed, as has the text in the quote) ..... a challenge .... 'If I had the time I could pull his arguements to bits' .... to save time here are the variables(facts) ....

Feel free to use my average costs as an example (Costs inclusive of VAT and dual fuel discounts) .... If my figures are not considered as being readily obtainable please feel free to check on any cost comparison website ......

Gas - 2.7745p/kWh
Electricity - 8.5833p/kWh

The best tariff currently available on cost comparison websites for electricity only supply shows cost/kWh as Rate1=17.74p(to 900kWh)/Rate2=6.96p/E7=3.36p

Daily hot water heat replenishment requirement for this exercise can be assumed to be 6kWh (2190kWh/Yr) - this is conservative and to PassivHaus standards, UK average is 14kWh, building standards is 10.4kWh ...... (Mine is currently below 6kWh and provided by an 'A' rated gas condensing boiler).

Electric immersion heater rated at 3kW

Location - Meriden, England ... 52°26'10" North, 1°38'47" West (just because it's in the middle and provides a fair average insolation)

Array 3.3kWp on a 35 Degree south facing roof (because this is near to optimal)

pv Daily output from 3.3kWp system by month from PVGIS (because the PVGIS database provides the basis of insolation data for pv software)

Mth/Daily kWh
01 3.11
02 5.05
03 7.10
04 10.2
05 11.6
06 11.4
07 11.7
08 10.5
09 8.74
10 6.00
11 3.61
12 2.24

Average Daily Generation 7.62kWh/Day
Total Generation 2780kWh

Expect generation from a 3.3kWp array to be .......

25% of annual power below 700W production
50% below 1600W
75% below 2400W
3% above 3000W (If not limited by the inverter)


Well that saves the time in researching all the variables (these are the facts) ..... and the answer is ??? ...... (well I'm waiting to see if solar pv is cheaper than gas or E7 electricity, even if the others aren't !!)


...............

Now then .......... 'but he ASSUMES no one can read their electricity bills and compare them to last years.' ...... my energy bills for 2010 were lower than those for 2009, but I don't really know how much lower they were on a direct comparison of either cost or energy consumed due to the difference in ambient temperatures between this year and last ..... I could make a very good guess because I have a detailed energy usage and ambient temperature history analysis going back over more than 6 years ...... If I can't do it directly and easily from the energy bills without reference to the collected data, I doubt there are many who could .....

To keep thing simple, let's leave the loophole out of the discussion for this one, I'd like to see anyone provide a calculation to say that a standard 240V immersion heater being run on solar pv supplimented by imported daytime electricity could work out cheaper than either gas or E7. The variables (facts) are there, now what's the calculation and the answer .... I could do with a :rotfl:

I'd be interested to see if anyone who actually has a sub 4kWp system believes that it is possible to save money by heating water with a standard immersion heater by using their pv and daytime electricity instead of E7 or gas ......

OK, now I've got a few minutes, thanks for once again, proving my point so well.

No one cares how efficient YOUR boiler is. My comments were aimed at Cardew who commented about a rajjack saying he was using his immersion, to which I responded that he was making a lot of assumptions. So you go away and google a few numbers, all of which I'm very familiar with but doesn't alter the fact that Cardew was ASSUMING things.

No one is suggesting that you use an immersion all the time.
However, over peak generation time, (summer months, over lunch), you could easily be generating not far off 3kw.
If you are sensible and have no other big appliances on, your total demand, including background needs will be slightly over 3kws.
This is not unrealistic if you plan your day well, or better still, out at work, and leave the immersion on a timer.
In many cases, 1 hour will be enough, but this will be governed by how much water you draw off later, how well insulated the tank is etc. But it is not unreasonable to say that with decent planning, your increased cost from having the immersion on will be very low and that will be offset by the other savings you will make through the long bright days of summertime, so you will still have a lower electric bill AND lower gas bills.
Sticking with the gas boiler though, the average boiler efficiency in this country is around 80%, though could be as little as 55%. But with an 80% efficient boiler, to get the same 3kw of heat, requires approx 4kw of gas being bought, in simple terms. So the difference in price then looks a lot less attractive, and you will still need electricity to run the pump on the gas central heating, mine being around the 200w. And if you are generating 3kw, and only using 500 watts, the excess 2.5kw will go into the grid. Under one of the rent a roof schemes you get nothing for that, but even if you've bought the panels, and receiving the FITs yourself, you will only get back 3p per kwh, which doesn't even cover the price of the gas.

So to surmise, it is easily the case, that you could get away with using an immersion instead of a gas boiler, with careful planning, and get much lower bills,but it all depends on your exact situation which no-one on this forum knows SO THEY ARE ASSUMING THINGS TO HELP THEIR OWN ARGUMENT.

And its no good going on about ambient temperatures affecting bills, etc etc, you just don't get it do you.
People come on moneysavingexpert for advice how to reduce their bills, the clue is in the name, they don't care how it happens if they end up with lower bills and of course there are a lot of factors. This year I might eat salads all year and last year, ate stews all year, but what is clear as everyone knows, is that bills generally are going up, year on year, and people are looking to save some money. Though some of you have a clear dislike for how this scheme is operating, an increasing number of people are coming on and saying they have saved £xs. So far, I haven't seen anyone come on and say their bills have increased after having ASG fit panels on the roof!

energysavingexp

K4blades wrote: »

OK, now I've got a few minutes, thanks for once again, proving my point so well.

No one cares how efficient YOUR boiler is. My comments were aimed at Cardew who commented about a rajjack saying he was using his immersion, to which I responded that he was making a lot of assumptions. So you go away and google a few numbers, all of which I'm very familiar with but doesn't alter the fact that Cardew was ASSUMING things.

No one is suggesting that you use an immersion all the time.
However, over peak generation time, (summer months, over lunch), you could easily be generating not far off 3kw.
If you are sensible and have no other big appliances on, your total demand, including background needs will be slightly over 3kws.
This is not unrealistic if you plan your day well, or better still, out at work, and leave the immersion on a timer.
In many cases, 1 hour will be enough, but this will be governed by how much water you draw off later, how well insulated the tank is etc. But it is not unreasonable to say that with decent planning, your increased cost from having the immersion on will be very low and that will be offset by the other savings you will make through the long bright days of summertime, so you will still have a lower electric bill AND lower gas bills.
Sticking with the gas boiler though, the average boiler efficiency in this country is around 80%, though could be as little as 55%. But with an 80% efficient boiler, to get the same 3kw of heat, requires 5kw of gas being bought, in simple terms. So the difference in price then looks a lot less attractive, and you will still need electricity to run the pump on the gas central heating, mine being around the 200w. And if you are generating 3kw, and only using 500 watts, the excess 2.5kw will go into the grid. Under one of the rent a roof schemes you get nothing for that, but even if you've bought the panels, and receiving the FITs yourself, you will only get back 3p per kwh, which doesn't even cover the price of the gas.

So to surmise, it is easily the case, that you could get away with using an immersion instead of a gas boiler, with careful planning, and get much lower bills,but it all depends on your exact situation which no-one on this forum knows SO THEY ARE ASSUMING THINGS TO HELP THEIR OWN ARGUMENT.

And its no good going on about ambient temperatures affecting bills, etc etc, you just don't get it do you.
People come on moneysavingexpert for advice how to reduce their bills, the clue is in the name, they don't care how it happens if they end up with lower bills and of course there are a lot of factors. This year I might eat salads all year and last year, ate stews all year, but what is clear as everyone knows, is that bills generally are going up, year on year, and people are looking to save some money. Though some of you have a clear dislike for how this scheme is operating, an increasing number of people are coming on and saying they have saved £xs. So far, I haven't seen anyone come on and say their bills have increased after having ASG fit panels on the roof!

you would be better of using solar hot water panels they are much more efficient.
and as for not using the eleccy during the day and it going back in to the grid some people still gain if their meters go backwards

grahamc2003

K4blades wrote: »

OK, now I've got a few minutes, thanks for once again, proving my point so well.
No one cares how efficient YOUR boiler is. My comments were aimed at Cardew who commented about a rajjack saying he was using his immersion, to which I responded that he was making a lot of assumptions. So you go away and google a few numbers, all of which I'm very familiar with but doesn't alter the fact that Cardew was ASSUMING things.!

Well of course in situations like this, some assumptions have to be made. The point is whether those assumptions are reasonable or not (and we'll see later that yours are not).

k4blades wrote: »

No one is suggesting that you use an immersion all the time.
However, over peak generation time, (summer months, over lunch), you could easily be generating not far off 3kw.

Yes, but you're also more likely to be generating less that 3kw, if you are talking about say 12:00-14:00 during jun/jul/aug/sep (hey an assumption again! - I've got to because you didn't tell us exactly the times you were thinking of.

k4blades wrote: »

In many cases, 1 hour will be enough, but this will be governed by how much water you draw off later, how well insulated the tank is etc. But it is not unreasonable to say that with decent planning, your increased cost from having the immersion on will be very low and that will be offset by the other savings you will make through the long bright days of summertime, so you will still have a lower electric bill AND lower gas bills.

You have simply made an assertion (which I think is obviously incorrect). I think Zuepater posted info so you could do a quantitative analysis (i.e. using numbers rather than words), and not a non-numeric analysis with an assertion at the end

k4blades wrote: »

But with an 80% efficient boiler, to get the same 3kw of heat, requires 5kw of gas being bought, in simple terms.

At least we now have some numbers. Unfortunately they are wrong. For 3kwh (not kw, which is power) of heat from an 80% efficient gas boiler you need 3.75kwh of gas, not 5kwh.

k4blades wrote: »

So to surmise, it is easily the case, that you could get away with using an immersion instead of a gas boiler, with careful planning, and get much lower bills

An incorrect assertion again. I'd say it is impossible to get MUCH lower bills using immersion heater rather than gas. For a start, you say you'd need 1 hour per day, at 3kw, is 3kwh which costs about 11p in gas. So the cost in gas for a full year is £40. So any theoretical or possible savings would be less than this (much less)

k4blades wrote: »

SO THEY ARE ASSUMING THINGS TO HELP THEIR OWN ARGUMENT.

No, I've read Cardews posts, and when he makes assumptions, they are reasonable, as are mine. Yours aren't.

k4blades wrote: »

People come on moneysavingexpert for advice how to reduce their bills, the clue is in the name, they don't care how it happens if they end up with lower bills and of course there are a lot of factors. This year I might eat salads all year and last year, ate stews all year, but what is clear as everyone knows, is that bills generally are going up, year on year, and people are looking to save some money. Though some of you have a clear dislike for how this scheme is operating, an increasing number of people are coming on and saying they have saved £xs. So far, I haven't seen anyone come on and say their bills have increased after having ASG fit panels on the roof!

True. By having more (correct) information, people can save more money with their panels. If they hgave duff information, then they can and will get higher bills. For instance, if people use an immersion heater to heat water (at midday) as opposed to using gas (or E7), then it's likely bills will be higher. I explained in detail why that was the case just a few days ago (using e7 as the substituted energy, as opposed to gas, but the argument is exactly the same.

I post here, and I expect Cardew is the same, to help people maximise their savings of energy bills. (I'm sure you do too, but I'm afraid you are giving out poor and incorrect information, imv).

zeupater

Agree with grahamc2003's post .....

A 3.3kWp system would only be producing enough energy to power a 3kW immersion for around 25 hours in a whole year, and that only being possible if the AC output is not limited by the inverter ... The data given is the data, the reasons for selecting the data are given and are reasonable ... the 6kWh water per day is assuming very low (PassivHaus) standards and is therefore well below the UK average (data given) ... gas was given as an example for comparison, E7 costs were provided for direct comparison .....

I have seen no attempt to provide a solution to the challenge which uses the data provided and therefore presume that one is not possible ....... If anyone thinks that any of the data provided for the challenge is in any way unreasonable, please provide details why, and what the alternative should be (with supporting evidence) and, if sensible, the challenge parameters can be modified.

Anyone actually considering heating water this way ..... please read your import meter before attempting this and then immediately afterwards and do this on the sunniest day you can find ... DO NOT put your immersion on a daytime timer and leave it on timer if you have either E7 or gas as an alternative energy source without first testing and/or considering the consequences, after that, if you wish to do so it is your own decision ..... please also note, absolutely no-one who currently has pv, either rent-a-roof or self owned, has supported the use of a standard immersion heater in the way proposed on this thread .... are we wrong ?

John_Pierpoint

Presumably it would be possible to fit the tank with a small immersion heater and use that say 5 hours per day?

(I used to have an immersion heater with two elements - one for overnight and one for a day time top up if the E7 hot water ran out. Now that there are only two of us in the household; the E7 heat does not run out - so when the main element "died" (split) I replaced the whole thing with a normal corrosion resistant element, costing about half the price).

Cardew

K4blades

I really do find your stance on this thread extraordinary, including the deleted abusive post. Doubtless, due to a clash we had earlier, you seem determined to gain some revenge.

I am on record for stating my dislike of the ‘rent a roof’ scheme but why would that lead me to offer misleading advice to participants, or those who have purchased a system? So I fail to see the logic of you saying: “SO THEY ARE ASSUMING THINGS TO HELP THEIR OWN ARGUMENT.”

Graham2003 and zeupater have rather clinically exposed the flaws in your assumptions, calculations, logic and advice and needs no further amplification.

zeupater

John_Pierpoint wrote: »

Presumably it would be possible to fit the tank with a small immersion heater and use that say 5 hours per day?

(I used to have an immersion heater with two elements - one for overnight and one for a day time top up if the E7 hot water ran out. Now that there are only two of us in the household; the E7 heat does not run out - so when the main element "died" (split) I replaced the whole thing with a normal corrosion resistant element, costing about half the price).

Hi John

That's much closer to being a reasonable solution, but I doubt that with the standard background loads you'd even be able to do it with a 1kW element without tripping over to import on a regular basis over a full six hour (average 6kWh) water heating period.

The real answer seems to be an intelligent setup such as http://www.coolpower.ie/brochures/EMMA_Microgenerator_Manager_CoolPower_0911v3_Web.pdf , however as I've been informed that they're around the £1500 mark and have an inverter equivalent lifespan, I doubt I'll be investing in one for a while ..... a price of below £100 would be different though ..... wonder if the 'rent-a-roof' companies are thinking of supplying these FOC within their packages to help their 'supply base' make better use of their power ..... :rotfl:

Anyway, sorry to see that your current wiring would prevent you from using daytime rate electricity instead of E7 to save money ....