Solar Panels UK - is it worth it?

[Yachtsman]

Yeah, your use is very low. In fact so low, all your new solar & battery kit is more for your EV Charging I guess.

Compare it to our house

Last week our average daily use was 60 kWh... nearly 10 times your daily average... even more the week before.

I assume you are a youngish family with children still at home, else how do you consume that much.
In contrast we are two retired very active seniors out most days enjoying life. Our house is 8 years old 4 x db, extremely well insulated.
All our lighting is LED & appliances are A+ rated. Our default consumption is fridge/freezer, security system, 2 x routers, 2 x bathrooms with underfloor heating, security cameras, automated house surround lighting during darkness + internal lights during darkness, garden water feature, electric security gates, motion triggered flood lighting internal & external Christmas lights (currently).
We are all electric except heating & hob.
It’s obvious that any PV + battery system I purchase will have an extra long ROI, I’m likely to have downsized & moved nearer grandchildren a long time before.

 

[PITA]

I assume you are a youngish family with children still at home, else how do you consume that much.
In contrast we are two retired very active seniors out most days enjoying life. Our house is 8 years old 4 x db, extremely well insulated.
All our lighting is LED & appliances are A+ rated. Our default consumption is fridge/freezer, security system, 2 x routers, 2 x bathrooms with underfloor heating, security cameras, automated house surround lighting during darkness + internal lights during darkness, garden water feature, electric security gates, motion triggered flood lighting internal & external Christmas lights (currently).
We are all electric except heating & hob.
It’s obvious that any PV + battery system I purchase will have an extra long ROI, I’m likely to have downsized & moved nearer grandchildren a long time before.

Haha... well, not really young. Early 50's, Semi-Retired. Work from home for last 20 years.

Wife, Me & 21 year old son. Similar to your house, fully smart home enabled, Induction Cooking, Electric Showers, Heat Pump Climate Control, Tesla M3P EV. We drive to National Trust sites regularly for walks etc... other than that, stayed at home all through the past 18 months. No problem.

 

[Yachtsman]

Haha... well, not really young. Early 50's, Semi-Retired. Work from home for last 20 years.

Wife, Me & 21 year old son. Similar to your house, fully smart home enabled, Induction Cooking, Electric Showers, Heat Pump Climate Control, Tesla M3P EV. We drive to National Trust sites regularly for walks etc... other than that, stayed at home all through the past 18 months. No problem.

I’ll bet it’s the heat pump. We have 2 x showers run of the gas boiler.
I wish I’d installed a PV system when the house was finished 8 yrs ago.
The wife thinks Ive lost the plot since our electricity bills are low, maybe she’s right, she usually is apparently.

 

[MrBadger]

The wife thinks Ive lost the plot since our electricity bills are low, maybe she’s right, she usually is apparently.

Another important lesson that some installers fail to grasp - you probably cannot save more money with PV than the electricity costs you without PV. Although previous FIT rates did on paper allow this (we get over £600/year which is pretty close to our annual electricity bill but its treated as capital outlay repayment rather than electricity savings), its unlikely to be the case now.

 

[RedMod3]

I enquired with Tesla about a Powerwall 2 months ago and no response yet. We have a 16 panel 4kW solar array that generates 4.3MWh a year, but being all electric and having a lot of IT running, our steady state power consumption is 1.1kWhr, but more when our air-air heat pumps are heating in winter and cooling in summer.

I reckon a single power-wall would do the job on Octopus GO; I need to chase Tesla up.

 

[Avendit]

Has anyone got a good spreadsheet for working out how well your consumption might fit with PV generation?

I've been looking at a 4ish KW I stall via so.energy (they claim to be able to do this for around £4k), and I have a good idea of our house's baseline consumption, but I've not tried to model time of day usage yet.

With an ASHP and the M3 consumption really doesn't line up time of day or time of year with generation, but I'm unsure that a 5 or 10kw battery makes much of a dent. But I do like the idea of some independence and really just see it as off setting some of our soon to be massive bills. The ASHP can be 50kw on a cold damp day so really we should probably spend on more insulation first.

(1960's detached challet style house, cavity wall insulation, spray foam in the roof and under the floor, but lots of bad dormer windows and other exceptions. 2 kids under 10 so LOTS of HW usage. Edinburgh with a reasonable SW facing roof)

Time to go to the next level with the spreadsheet I think.

 

[Tony Hoyle]

I''d go insulation over everything first.. then when you've maxed that out think of other savings. I'd get double/triple glazing everywhere.. maybe get someone to point a flir at your house to see where the hot spots are. eg. in this house it won't drop more than a couple of degrees overnight in winter - that's a saving in heating bills far in excess of the gain from solar during the day.

 

[Avendit]

I''d go insulation over everything first.. then when you've maxed that out think of other savings. I'd get double/triple glazing everywhere.. maybe get someone to point a flir at your house to see where the hot spots are. eg. in this house it won't drop more than a couple of degrees overnight in winter - that's a saving in heating bills far in excess of the gain from solar during the day.

Yea, writing the above made me think this. I have a flir, but I struggle to get super info out of it as surfaces are generally at ambient temps - it's the flow I need to see. Good for finding drafts tho.

The house needs rendering after some work last year, plan is to combine that with some EWI, which should take the main walls down to a u value of about 0.14 (and give the whole work at a 5% VAT). The recent extension was built to 0.22, then I have to rebuild a bathroom dormer that is really badly insulated. That's all happening any way, it's whether to add panels -as well- or if our consumption is just too much the inverse of what can be generated.

 

[PITA]

I''d go insulation over everything first.. then when you've maxed that out think of other savings. I'd get double/triple glazing everywhere.. maybe get someone to point a flir at your house to see where the hot spots are. eg. in this house it won't drop more than a couple of degrees overnight in winter - that's a saving in heating bills far in excess of the gain from solar during the day.

That's exactly how I did it... cleared out loft, sheep wool deep insulation, new 28mm profile double glazed with 6mm laminate glass, new doors all Secured by Design with laminate double glazed. No cracks or draughts. White thermal blackout blinds on all windows.

Walls were already cavity wall insulated. Took out gas fires, took out gas hob. Installed electric showers, emersion heater for hot water, induction hob, electric cooker, microwave...

Kept the gas boiler central heating, scheduled with thermostatic radiator valve zone control. Works alongside heat pump.

Heat Pump wall units do dehumidifying, air filtration & air condition as well... next year I want to install a mechanical ventilation & heat recovery (MVHR) system

 

[RedMod3]

Heat Pump wall units do dehumidifying, air filtration & air condition as well... next year I want to install a mechanical ventilation & heat recovery (MVHR) system

MVHR is great to eliminate condensation in an airtight place and it gets rid of moisture. Makes the property feel very fresh and not musty.

 

[26ct2143]

Has anyone got a good spreadsheet for working out how well your consumption might fit with PV generation?

I've been looking at a 4ish KW I stall via so.energy (they claim to be able to do this for around £4k), and I have a good idea of our house's baseline consumption, but I've not tried to model time of day usage yet.

With an ASHP and the M3 consumption really doesn't line up time of day or time of year with generation, but I'm unsure that a 5 or 10kw battery makes much of a dent. But I do like the idea of some independence and really just see it as off setting some of our soon to be massive bills. The ASHP can be 50kw on a cold damp day so really we should probably spend on more insulation first.

(1960's detached challet style house, cavity wall insulation, spray foam in the roof and under the floor, but lots of bad dormer windows and other exceptions. 2 kids under 10 so LOTS of HW usage. Edinburgh with a reasonable SW facing roof)

Time to go to the next level with the spreadsheet I think.

Firstly write off 1st Nov to 1st Mar as near zero output. This time of year sun is low, always cloudy and short day length.
I'm currently doing about 2.5 kwh / day on a 30 KW array.

 

[Avendit]

MVHR is great to eliminate condensation in an airtight place and it gets rid of moisture. Makes the property feel very fresh and not musty.

For anyone reading that isnt in a new build built to airtightness standards, I think you do need to get a measure of airtightness before doing this as a retrofit? With a leaky house the benefits of MVHR quickly disappear I believe? (Have also considered this but we have a long way to go first!)

 

[Zakalwe]

I'm waiting for a 5.2kWh PV and 8.2kWh battery system to be commissioned. I'm lucky to have a due south roof with no shading on this house, which I moved into in the summer. Its a fairly new house (2 years old) with gas CH and hot water. It seems pretty efficient to run- gas is currently less than my mid-80's previous house (old was 4 bed, new is 5 bed with nearly twice the floor space).

My current thinking is to use the PV and Octopus Go to charge the batteries and then discharge during the night and following day. Hopefully that will shift most if not all of my consumption to the cheap 5 hour 5.5p/kWh period. Depending on consumption I will fit a solar diverter to heat the hot water. WIth a bit of luck this should reduce my gas consumption to zero in the summertime.

 

[MrBadger]

For anyone reading that isnt in a new build built to airtightness standards, I think you do need to get a measure of airtightness before doing this as a retrofit? With a leaky house the benefits of MVHR quickly disappear I believe? (Have also considered this but we have a long way to go first!)

Based on my experience, MVHR in non airtight house will work just fine.

We have a well insulated house, but far from air tight, although we started getting a few issues the more we insulated and/or blocked off the easy win air holes. We retrofitted MVHR nearly 5 years ago and it cured the issues that we were having with no detrimental issues including (apart from installation) cost.

Benefit in summer in a very hot house is perhaps not as good as I was hoping (even on summer bypass, its nice to have some windows open in the evening to get air flowing), but that's the only part that has not worked well. Including a couple of filters annually, I recon its costing around £50/year £90/year to run although difficult to tell change in heating costs as they vary from year to year - certainly nothing obvious. The alternative of leaving windows open would be far more costly.

We went into it eyes wide open knowing that it would probably be non optimal, but instead of throwing good money after bad (sticking plaster solutions), we went for it knowing that over time the rest of the house would be further bought up to scratch - we oversized the system a little and know that over time it will become be even more beneficial. You can certainly feel the suck of air on a couple of places, especially interior doors of the extract rooms, but no drafts. Ironically the extract rooms are largely unheated ('wet' rooms, a couple with occasional meagre towel rail use) and whilst our FLIR can tell that incoming ducted air is a few degrees lower than the heat of the room, you don't notice (unless you put back of hand right next to the vent) and it far better and controllable than leaving a window open.

Expensive yes, but its the gold standard solution and we are very happy with it and its saved on some potential deterioration in the fabric of the house and contents. No regrets once I had got over the installation cost and mess...

 

[Yachtsman]

I'm waiting for a 5.2kWh PV and 8.2kWh battery system to be commissioned. I'm lucky to have a due south roof with no shading on this house, which I moved into in the summer. Its a fairly new house (2 years old) with gas CH and hot water. It seems pretty efficient to run- gas is currently less than my mid-80's previous house (old was 4 bed, new is 5 bed with nearly twice the floor space).

My current thinking is to use the PV and Octopus Go to charge the batteries and then discharge during the night and following day. Hopefully that will shift most if not all of my consumption to the cheap 5 hour 5.5p/kWh period. Depending on consumption I will fit a solar diverter to heat the hot water. WIth a bit of luck this should reduce my gas consumption to zero in the summertime.

That’s exactly my thinking except mine would be a 4.5kWp system & 10 or 14.5 kW storage.

 

[Zakalwe]

That’s exactly my thinking except mine would be a 4.5kWp system & 10 or 14.5 kW storage.

I've used Givenergy's 5kWh inverter so I can always add additional batteries to it. Civen the option of more PV or more batteries, I think that batteries would be the better option.

 

[RedMod3]

For anyone reading that isnt in a new build built to airtightness standards, I think you do need to get a measure of airtightness before doing this as a retrofit? With a leaky house the benefits of MVHR quickly disappear I believe? (Have also considered this but we have a long way to go first!)

Our place was built in 1989, and we have no chimney. We know that we are pretty airtight as if a window is open, closing external doors is a lot easier than when all windows are closed. We don't as a general rule ever have windows open - winter or summer. I've also set the fans to have a slightly positive air-pressure inside the property.

 

[RedMod3]

Our place was built in 1989, and we have no chimney. We know that we are pretty airtight as if a window is open, closing external doors is a lot easier than when all windows are closed. We don't as a general rule ever have windows open - winter or summer. I've also set the fans to have a slightly positive air-pressure inside the property.

I’ve just taken this pic of our controller. The heat exchanger is heating up incoming air from 6.9°C to 13.6°C, while extracted air from wet rooms at 15.4°C gets blown out at 8.8°C after the heat is removed.

We use a Genvex system, what’s your’s Vanilla?

I need to chase up Tesla re a Powerwall.

 

[kitenski]

Firstly write off 1st Nov to 1st Mar as near zero output. This time of year sun is low, always cloudy and short day length.
I'm currently doing about 2.5 kwh / day on a 30 KW array.

that's far from my experience, with 11 year old panels on a south facing roof in Leeds.

 

[Dilly]

Good news. The days start getting longer from today