Solar panels and battery - any real world reccomendations?

[BUDFORCE]

How much battery you need really depends on your usage pattern. There like everything else with solar is probably not a perfect solution since you can affect change to get most benefit from many scenarios. Such as you mention, use the white goods on sunny days close to peak generation as much as possible.

This is it really.

Batteries are not right for all setups.

Id say if you have a large, south facing roof so can have a lot of panels, and generate a lot of energy, and you are also a say high electicity user, and also dont work from home, then absolutely.

Although the outset cost will be very high, you may end up almost have a nil eletricity bill in the summer, and significantly reduced during the winter, and that can really start adding up the savings and payback time.

On the flip side of that, if your roof isnt ideal, so you cant generate masses in the first place, and you work from home and get savy with using your washing machine etc during peak generation, you are probably not going to benefit, and that is where you really have to start looking at the statistics and try and work out if its worth while.


I mean, solar panels in general, are by any means a perfect solution, they tend to generate a lot of energy in peaks, and often when you are least likely to use it, whilst during those cold dark winters when your usage is up, they generate the least.


One thing I will say is if you are not getting a battery, and you have a hot water tank, we are getting a device installed that diverts excess into the hot water tank, and it was a very cheap extra. Whilst we have oil fired hot water, there is an immersion heater (which we dont often use) but with the excess energy going to that, it should save a bit of oil. Its also a thing unlike a battery that in theory lasts forever, so like the panels, will pay itself back, id say pretty quickly.

 

[Freakbro]

Just had TCL Solar round for their quote (he said he's had about 10 enquiries coming from this forum! ) and for 7.5KW of panels (20) and 9.6KW of battery was £13.8K

More than I was expecting but still a favourable price to the last quote, from the national company, which was 6.1KW of panels (16) and 7.2KW of battery for £14.8K

We are quite high users, being domestic and business, currently at ~8.5k KWh / yr, which now I've moved in and WFH, plus have a thirsty A/V setup to bring over yet, then I think well easy end up at 10k KWh / yr.

Based on that usage, and the estimated savings of 6k KWh / yr (conservatively) at say the estimated Oct cap price of 34p it'll take just under 7 Yrs to pay for itself. Still, it's a lot to outlay now, decisions decisions.

We have a 25m S-SW facing roof that the panels can go on.

 

[Mercenary Keyboard Warrior]

One thing I will say is if you are not getting a battery, and you have a hot water tank, we are getting a device installed that diverts excess into the hot water tank, and it was a very cheap extra. Whilst we have oil fired hot water, there is an immersion heater (which we dont often use) but with the excess energy going to that, it should save a bit of oil. Its also a thing unlike a battery that in theory lasts forever, so like the panels, will pay itself back, id say pretty quickly.

Is this literally just a device to use the immersion heater already fitted?
I have a megaflow so had kind of ruled out allowing anyone to mess what that, but if its just using the existing immersion element I need to look at that as well!

 

[BUDFORCE]

Is this literally just a device to use the immersion heater already fitted?
I have a megaflow so had kind of ruled out allowing anyone to mess what that, but if its just using the existing immersion element I need to look at that as well!

Yup literally that, we also have a megaflow, basically wire it almost straight into the element so excess energy just gets dumped into that.

In many ways like a battery.

 

[Mercenary Keyboard Warrior]

Yup literally that, we also have a megaflow, basically wire it almost straight into the element so excess energy just gets dumped into that.

In many ways like a battery.

Thanks I will deffo look into that as well then
We have our water on before we get up to shower so the tank is refilled but not heating until the evening, so that could be a perfect solution to soak up some excess energy as well
I assume its got some kind of link to water temp as well just like the controls for the immersion so seems a really good idea, and virtually no hardware to add, seen it mentioned but had assumed it was a more significant change

 

[HungryHippos]

Yeah I couldn't do it because my hot water is part of my combi system, but I think it's a good way of using excess generation without reliance on a battery setup if you have a tank.

 

[BUDFORCE]

Thanks I will deffo look into that as well then
We have our water on before we get up to shower so the tank is refilled but not heating until the evening, so that could be a perfect solution to soak up some excess energy as well
I assume its got some kind of link to water temp as well just like the controls for the immersion so seems a really good idea, and virtually no hardware to add, seen it mentioned but had assumed it was a more significant change

It'll just work off whatever your termostat is set to for your immersion.

If its anything like mine, where the element is for your immersion heater, there will be a thermostat on it, usually with a little arrow or dial that twists around. You might have to unscrew a plastic plate to see it. I know that because I had to replace mine once, but easy job about £20 part.

It'll basically just heat the water constantly until it hits whatever temp that is set to. So completely independent of the rest of your heating system.

I know the temptation would be to set that really high because your storing more energy but I probably wouldnt, we have had issues with the pressure relief valve and I reckon its because I used to have the thermostat way up on the immersion, and the odd occasion it got left on the water would be scalding hot, way hotter than it gets from the oil boiler.

But yeah, plenty of hot water on those hot sunny days, just when you need it right?

Sarcasm aside it should save a bit of oil during the summer as your afternoon/evening hot water is effectively free.

 

[Journey]

You can only use so much water though, and if you don't use all of the hot water you have wasted energy. Balancing export, battery charging and water heating etc. is a learning curve. You can be paid 7.5ppkWh to export your solar, and then if you put yourself on a good tariff, just use your immersion if you 'need' the water, back from the grid at 7.5ppkWh or from your battery if it's at a strange hour.
Not to mention very few people actually measure appliance draw directly for use in peak/off-peak scenarios, as an example an large load of washing 8Kg+ at 40c uses 0.53kWh, I know this as I have measured it several times on a sunny day that is such a small amount of generation in the spring/summer and again you can only do some much washing. I've not got a dishwasher, ironically, so can't see how much a cycle would use, but when I used to have one it was on once a day at most.

 

[BUDFORCE]

@Mercenary Keyboard Warrior

https://www.marlec.co.uk/wp-content/uploads/2016/02/Solar-iBoost-Brochure-v3-A4-3pg.pdf

Is the product borchure.

 

[SoliD]

Not to mention very few people actually measure appliance draw directly for use in peak/off-peak scenarios, as an example an large load of washing 8Kg+ at 40c uses 0.53kWh, I know this as I have measured it several times on a sunny day that is such a small amount of generation in the spring/summer and again you can only do some much washing. I've not got a dishwasher, ironically, so can't see how much a cycle would use, but when I used to have one it was on once a day at most.

Had to get a new washing machine the other week and it has an energy meter built in(Samsung smartthings) and surprised me how little energy the thing actually uses on the eco and active wear cycles which are my predominant uses.

 

[Mercenary Keyboard Warrior]

You can only use so much water though, and if you don't use all of the hot water you have wasted energy. Balancing export, battery charging and water heating etc. is a learning curve. You can be paid 7.5ppkWh to export your solar, and then if you put yourself on a good tariff, just use your immersion if you 'need' the water, back from the grid at 7.5ppkWh or from your battery if it's at a strange hour.
Not to mention very few people actually measure appliance draw directly for use in peak/off-peak scenarios, as an example an large load of washing 8Kg+ at 40c uses 0.53kWh, I know this as I have measured it several times on a sunny day that is such a small amount of generation in the spring/summer and again you can only do some much washing. I've not got a dishwasher, ironically, so can't see how much a cycle would use, but when I used to have one it was on once a day at most.

We have to heat the tank though, you cant only heat half the tank, so if I use say 100 litres in the morning and its replaced by 100 litres of cold, by the evening the boiler is going to kick in and heat back up to the whole tank being at target temp.
So its kind of irrelevant if I have used 10 litres or 100 litres that morning, in the evening its going to replace the used plus heat loss, via the boiler.
So if the tanks almost at temp come evening then the boiler will do naff all. If I have already charged a battery then using the excess before sending to the grid seems sensible. Gas prices are going up quickly so the gap between them is closing.

From what I can tell its almost impossible right now to switch to a supplier who offers a good off peak rate. When I looked a month or so ago it wasn't an option, all moves were to fixed at higher costs than I am on. So I need to stay with BG for now.
BG offer a two tier but its 2p a unit more in peak for 10p a unit less off peak. Its maybe worth the switch but its not massive savings to be had.

I think short term its going to have to be just holding out until the market is less in a state of panic.

Ah i am just wondering if your assuming the immersion is normally used, its not, normal water heating is gas. In fact the immersion has never been on, Ive been meaning to test it actually works just in case!

 

[Mercenary Keyboard Warrior]

@Mercenary Keyboard Warrior

https://www.marlec.co.uk/wp-content/uploads/2016/02/Solar-iBoost-Brochure-v3-A4-3pg.pdf

Is the product borchure.

Thanks, will check it out.

 

[Journey]

Ah i am just wondering if your assuming the immersion is normally used, its not, normal water heating is gas. In fact the immersion has never been on, Ive been meaning to test it actually works just in case!

No, but as kWh pricing for gas is almost that of electricity, then you can get rid of the fossil burning and rely on your literally stored solar energy bet that in the grid or in the battery. My water gets heat when it is required, but I am in the midst of having a much more efficient system put in along with a heat pump, so things will only get better. The common issue is people still think you need to keep water warm all the time to use less energy when that just isn't the case.

If you haven't already got solar, it sounds easy on paper, but you'll soon find yourself looking at graphs and energy use, and patterns and thinking "ooooh, I didn't realise x"

 

[Journey]

Also to add to the hot water discussion, to boil a full kettle (will measure volume later) with water straight from the cold tap is takes only 0.138kWh, which is enough to do an entire sink full of dishes for the most part. Can someone please get a real life measurement for a dishwasher cycle?

 

[Mercenary Keyboard Warrior]

No, but as kWh pricing for gas is almost that of electricity, then you can get rid of the fossil burning and rely on your literally stored solar energy bet that in the grid or in the battery. My water gets heat when it is required, but I am in the midst of having a much more efficient system put in along with a heat pump, so things will only get better. The common issue is people still think you need to keep water warm all the time to use less energy when that just isn't the case.

If you haven't already got solar, it sounds easy on paper, but you'll soon find yourself looking at graphs and energy use, and patterns and thinking "ooooh, I didn't realise x"

Your really confusing.
Why would I use the battery to heat the water and then end up importing electric, i'm better heating my water with gas than using the harvested electric from the battery for my electric needs. At least with current pricing.

I've got a megaflow tank, I cant heat part of that and only heat the water I use, I have to heat a tank of water to use it.
The point in having it heated by excess solar is that if there is enough spare to do that as well prior to exporting it will reduce gas usage, I am sure the other poster is thinking along the same lines.
Im not going to start never heating my water until I want to use some, its not the 1950s here!

If during parts of the year we have enough excess solar to top the tank temp up then i would likely use negligible amounts of gas to heat water, the tanks efficient at not losing temp (when our heating broke we went about 36 hours and the water was decently hot, but as soon as we started using it it dropped as it was getting topped up with cold obviously). With our frequent usage the evening and morning heating would likely use hardly any gas when solar was in force well (Apr-Aug roughly). In the winter would be like now, gas morning and evening.

If you can explain how I can only heat half the water in my tank Im all ears since its a big tank and only two of us most of the time. Although the other half probably uses most of a tank when she has a near scolding bath some evenings!

 

[Journey]

Your really confusing

No I am not, you just didn't read what I said.

If you are generating lots of excess, you send it to the grid with SEG and get paid 7.5ppkWh, or charge your battery if not full already. If you need more water than you have, obviously it depends on the time of day when you personally use most, then you can heat using immersion for the same 7.5ppkWh you were paid at off-peak rates (mine is 20:30 to 01:30, think its 21:30 to 02:30 now or 00:00 to 04:30) or using excess battery energy, depending again on the time of day. You can then either recharge your pack at the off-peak rates if you were using it, or not. The net cost of a kWh is 0p if you are using the pass to grid, then re-import, or re-charge. However if you don't need all that hot water then for every kWh yuo put in you lost 7.5p. It's not that hard to understand.

Im not going to start never heating my water until I want to use some, its not the 1950s here!

That isn't what I meant, if you care about energy use and such, then you'll see why knowing when you need a resource is much more beneficial that wasting one. When you've had your system installed you'll start to understand better, if you want to make most use of it from an cost or environmental point-of-view.

 

[Mercenary Keyboard Warrior]

No I am not, you just didn't read what I said.

If you are generating lots of excess, you send it to the grid with SEG and get paid 7.5ppkWh, or charge your battery if not full already. If you need more water than you have, obviously it depends on the time of day when you personally use most, then you can heat using immersion for the same 7.5ppkWh you were paid at off-peak rates (mine is 20:30 to 01:30, think its 21:30 to 02:30 now or 00:00 to 04:30) or using excess battery energy, depending again on the time of day. You can then either recharge your pack at the off-peak rates if you were using it, or not. The net cost of a kWh is 0p if you are using the pass to grid, then re-import, or re-charge. However if you don't need all that hot water then for every kWh yuo put in you lost 7.5p. It's not that hard to understand.



That isn't what I meant, if you care about energy use and such, then you'll see why knowing when you need a resource is much more beneficial that wasting one. When you've had your system installed you'll start to understand better, if you want to make most use of it from an cost or environmental point-of-view.

Still makes no sense. I dont think your grasping how normal people live.
I think your assuming a lot in here but I cant be bothered to try to untangle it

When your posting about boiling a kettle to do washing up your clearly an edge case.

I'm out.

 

[Journey]

Still makes no sense. I dont think your grasping how normal people live.
I think your assuming a lot in here but I cant be bothered to try to untangle it

When your posting about boiling a kettle to do washing up your clearly an edge case.

I'm out.

What? I mention the power draw to illustrate how much something uses... but whatever man, you go ahead and ignore real work empirical data and off you tot putting 100's kWh's extra into your water tank every year that will go to waste.

Also normal people, lol. Normal people. Care to tell me what a normal person is then?

My life is organised enough to know when I'll need a shower, maybe that is beyond your capabilities.

I am also out. Whatever that means.

 

[BUDFORCE]

@Journey

Our relatively modern Bosch dishwasher uses 1kwh (near as damnit) per cycle on eco mode.

 

[Ron-ski]

@Journey exactly why I ripped out our old hot water tank and boiler, and fitted a stonking big combi around 17 years ago, could not see the point of heating a tank full of water twice a day.