Solar Panels UK - is it worth it?

[Drew57]

I can increase the limits on my inverter to account for high grid voltage during sunny days. Have you checked to see what yours are set to and considered bumping them up a couple of volts?

Yes, as with my reply to ACarneiro.

 

[Drew57]

The problem with AC coupled batteries working with hybrid inverters is that they tend to just drain the DC batteries. Hybrid inverters hide the DC batteries to the AC system and make it look like it's solar. So the AC ones will merrily charge away from them.

I'm not saying you can't get around it but unsure how (CT clamps probably don't work on DC), as was something I was looking at while waiting for Powerwall install (also AC batteries).

Set timed block discharge on the PV inverter. When the car charges the DC batteries are unaffected.

 

[phil4]

Set timed block discharge on the PV inverter. When the car charges the DC batteries are unaffected.

That works really well for defined times.

But as a general AC/DC working together through the day, it needs some software integration as thewishy mentions. Something the means the AC charger can see the inverter and know whether it's got solar to send out, and to stop it drawing from the DC batteries. And as thewishy says it needs to do that reasonably frequently.

For car charging as you say, you can just block the times and let it sort itself out.

 

[RedMod3]

I can increase the limits on my inverter to account for high grid voltage during sunny days. Have you checked to see what yours are set to and considered bumping them up a couple of volts?

Or you can ask your DNO to wind down the voltage on the transformer if it exceeds 253V.

 

[RedMod3]

thats really stupid. Why would you force discharge other than perhaps a calibration cycle. The PW even has specific settings to prevent it I thought? Shouldn’t that be equivalent to export limitation in some inverters and be enough for DNO?

No, because the DNOs believe the installers could make an error and allow export, so they take the discharge power into account - I've asked them btw.

 

[Drew57]

That works really well for defined times.

But as a general AC/DC working together through the day, it needs some software integration as thewishy mentions. Something the means the AC charger can see the inverter and know whether it's got solar to send out, and to stop it drawing from the DC batteries. And as thewishy says it needs to do that reasonably frequently.

For car charging as you say, you can just block the times and let it sort itself out.

The CT on our Zappi using Eco+ only allows a charge from Solar, never the batteries if they are full and excess is greater than 1.4kWh. If they are not full, excess goes to the batteries before the car.

On very sunny days as at the moment, Eco setting only uses excess generation so in both instances - overnight 7kWh or daytime using solar up to 3.6kWh the batteries aren’t drained.

 

[Mrklaw]

first full month with the battery - £23.30. About £13 of that is the blooming standing charge so a tenner for the electric isn’t bad. 31kwh for 31 days so averages to a kwh per day. I still think thats a little high if most of it is ‘inverter lag’ but there will have been some spikes for high loads being on etc but only for a few minutes.

 

[yessuz]

first full month with the battery - £23.30. About £13 of that is the blooming standing charge so a tenner for the electric isn’t bad. 31kwh for 31 days so averages to a kwh per day. I still think thats a little high if most of it is ‘inverter lag’ but there will have been some spikes for high loads being on etc but only for a few minutes.

remind me, what's your system size/config?

 

[phil4]

The CT on our Zappi using Eco+ only allows a charge from Solar, never the batteries if they are full and excess is greater than 1.4kWh. If they are not full, excess goes to the batteries before the car.

On very sunny days as at the moment, Eco setting only uses excess generation so in both instances - overnight 7kWh or daytime using solar up to 3.6kWh the batteries aren’t drained.

Yes, you can do that by setting the export margin on the Zappi to 50 or 100W, thus battery first, and won't drain the battery: https://support.myenergi.com/hc/en-...569-Using-a-battery-with-your-myenergi-system

The problem is an AC battery isn't a Zappi and so will drain the DC battery given half a chance.

 

[Mrklaw]

remind me, what's your system size/config?

2.6kwp south, 3.9kwp north (3kw inverter), 9.5kwh givenergy battery and AC3 ac coupled inverter

Edit: total 833kwh generated - 367kwh exported, 466kwh consumed (306kwh direct and 160 to battery)

That’s more than usual consumption - bit of AC, charging my wife’s egolf for two weekends and topping up my Tesla

 

[yessuz]

2.6kwp south, 3.9kwp north (3kw inverter), 9.5kwh givenergy battery and AC3 ac coupled inverter

ok, cool

 

[KennethS]

first full month with the battery - £23.30. About £13 of that is the blooming standing charge so a tenner for the electric isn’t bad. 31kwh for 31 days so averages to a kwh per day. I still think thats a little high if most of it is ‘inverter lag’ but there will have been some spikes for high loads being on etc but only for a few minutes.

That is impressive -- I really must look into somehow upping the PV on our home.

 

[Rirawin]

Looks like Ovo have just entered the solar panel installation game Home Solar Panels | Solar Panel Installation | OVO Energy

 

[ACarneiro]

Looks like Ovo have just entered the solar panel installation game Home Solar Panels | Solar Panel Installation | OVO Energy

Interesting prices but their "solar+battery" packages include a small battery of just 2.4kWh capacity. I suppose it's a decent buffer for a house that's being used all day and their export SEG rate is a very generous 20p/kWh so it hurts less when you're selling to the grid...

 

[thewishy]

Interesting prices but their "solar+battery" packages include a small battery of just 2.4kWh capacity. I suppose it's a decent buffer for a house that's being used all day and their export SEG rate is a very generous 20p/kWh so it hurts less when you're selling to the grid...

It'll do a good job of 1kw of Solar, but 3kw kettle type scenarios. It's certainly better than no battery. Obviously isn't going to keep the house running all evening...

 

[Mrklaw]

It'll do a good job of 1kw of Solar, but 3kw kettle type scenarios. It's certainly better than no battery. Obviously isn't going to keep the house running all evening...

Its one thing I wish mroe dashboards did - let you zoom in to a specific time period and get a report. So you could get an easy way to see how much energy you use eg between 7pm and 1:30am or between 4:30 and 7am. roughly speaking we seem to use about 20% of a 9.5kwh battery between 7pm and midnight, and the same again, maybe 25% between midnight and 7am. thats with the washing machine and dishwasher running overnight.

So its small, but like you said a good buffer to refill and smooth out demand, but if its full at the end of the day you may just get to an off peak rate window with it, then fill it up again for the morning. More is better though

 

[WannabeOwner]

the washing machine and dishwasher running overnight

Would they be better run during the day, when there is excess PV? I run my dishwasher on Intensive program, when used during the day (and Eco if used at night / Winter), because that cleans the machine better - and uses up some spare excess PV

zoom in to a specific time period and get a report.

PowerWalls have an export (CSV file of Solar PV, House consumption, Grid import and PowerWall (Charge/Discharge) which (from memory) is every 15 minutes. Maybe there is a similar (export) for your batteries? or an API where you could "pull" the data at a time interval of your choice?

if its full at the end of the day you may just get to an off peak rate window with it, then fill it up again for the morning. More is better though

I can get through the night ... just! ... on days when my PV exceeds house usage until 17:00 and PV carries on producing only dropping below 25% of house needs at 20:00

Its nip and tuck at Sunrise though I drop Reserve to 0% in anticipation of PV; PV ramps up to provide house requirements by 06:30 and jumps dramatically (to overproduce / charge battery) by 07:00. I figure if I was unfortunate enough to get a powercut at 06:29 so be it. But from 11:00 to 17:00 the batteries are full and I need to be charging a car or two!

But as @Pete UK (and no doubt others) have said, inadvertently buying some juice at Peak negates a massive amount of the effort expended on maximising the savings. My solution will be a 3rd battery so I'll have plenty for overnight, including if following day is cloudy, so apart from the capital outlay I'm with you on "More is better" - once the pain of the purchase has subsided.

 

[ACarneiro]

Would they be better run during the day, when there is excess PV? I run my dishwasher on Intensive program, when used during the day (and Eco if used at night / Winter), because that cleans the machine better - and uses up some spare excess PV



PowerWalls have an export (CSV file of Solar PV, House consumption, Grid import and PowerWall (Charge/Discharge) which (from memory) is every 15 minutes. Maybe there is a similar (export) for your batteries? or an API where you could "pull" the data at a time interval of your choice?



I can get through the night ... just! ... on days when my PV exceeds house usage until 17:00 and PV carries on producing only dropping below 25% of house needs at 20:00

Its nip and tuck at Sunrise though I drop Reserve to 0% in anticipation of PV; PV ramps up to provide house requirements by 06:30 and jumps dramatically (to overproduce / charge battery) by 07:00. I figure if I was unfortunate enough to get a powercut at 06:29 so be it. But from 11:00 to 17:00 the batteries are full and I need to be charging a car or two!

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But as @Pete UK (and no doubt others) have said, inadvertently buying some juice at Peak negates a massive amount of the effort expended on maximising the savings. My solution will be a 3rd battery so I'll have plenty for overnight, including if following day is cloudy, so apart from the capital outlay I'm with you on "More is better" - once the pain of the purchase has subsided.

Self consumption can be a very, very deep and expensive rabbit hole to go down (he says with his 4 PWs...)

 

[roadcred]

My solution will be a 3rd battery so I'll have plenty for overnight, including if following day is cloudy, so apart from the capital outlay I'm with you on "More is better" - once the pain of the purchase has subsided.

If you change your mind would be happy to take the PW off your installer (or let him install at mine)

 

[Mrklaw]

Would they be better run during the day, when there is excess PV? I run my dishwasher on Intensive program, when used during the day (and Eco if used at night / Winter), because that cleans the machine better - and uses up some spare excess PV

We do them overnight as habit from off peak. Dishwasher is convenient and I don't think we could wait until the next day of solar after dinner, we'd need to buy more stuff

also at least in summer its using solar in the battery and that carries us through with approx 50% on a good day before the sun starts again. As it gets less sunny we might need to revisit the washing machine though.