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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
Combination of increasing solar and sudden warm spell this weekend has suddenly seen our systems kick fully into shoulder season mode. Overnight battery load + solar is now seeing us through to 5/6pm and we just have the evening to pay full price on. Nice to see the smart meter stay at around £7 a day for heating, hot water and power.
We also spent the last couple of weekend's sealing and re-insulating one of our dormers. Taken it from 3cm of mineral wool and no air tightness measures to 20cm of PIR in the ceiling and 15cm in the walls and fighting as many drafts as we could.
Main point of interest to report back is that the smaller the gaps get, the harder the drafts seem to blow through them
. Think we got them all before closing everything back up.
That dormer is a bathroom, and WWHR is being installed. This should remove the need for an evening top up of the HW tank and save us £1-£1.50 a day. Real demonstrable ROI (although not as good as enforcing 4 minute showers would be, but I keep reminding myself this is not the way).
We also spent the last couple of weekend's sealing and re-insulating one of our dormers. Taken it from 3cm of mineral wool and no air tightness measures to 20cm of PIR in the ceiling and 15cm in the walls and fighting as many drafts as we could.
Main point of interest to report back is that the smaller the gaps get, the harder the drafts seem to blow through them
. Think we got them all before closing everything back up.That dormer is a bathroom, and WWHR is being installed. This should remove the need for an evening top up of the HW tank and save us £1-£1.50 a day. Real demonstrable ROI (although not as good as enforcing 4 minute showers would be, but I keep reminding myself this is not the way).
ha, this reminded me then I stayed in one of old Best Western hotels and once the bathroom door was closed, you could hear whistle from the draft going under the doorCombination of increasing solar and sudden warm spell this weekend has suddenly seen our systems kick fully into shoulder season mode. Overnight battery load + solar is now seeing us through to 5/6pm and we just have the evening to pay full price on. Nice to see the smart meter stay at around £7 a day for heating, hot water and power.
We also spent the last couple of weekend's sealing and re-insulating one of our dormers. Taken it from 3cm of mineral wool and no air tightness measures to 20cm of PIR in the ceiling and 15cm in the walls and fighting as many drafts as we could.
Main point of interest to report back is that the smaller the gaps get, the harder the drafts seem to blow through them
That dormer is a bathroom, and WWHR is being installed. This should remove the need for an evening top up of the HW tank and save us £1-£1.50 a day. Real demonstrable ROI (although not as good as enforcing 4 minute showers would be, but I keep reminding myself this is not the way).
WannabeOwner
Well-Known Member
Yea, we didn't rebuild the dormer, so cold bridging definitely still there, but we did layer up to reduce it. Maxed out in the studs, then new, off set, frame on top with more insulation, then insulated tile board or plasterboard ontop as appropriate. Did what we could in the corners, along the roof line etc with overlapping layers all ALU foiled over, but some compromises were inevitable.The better the insulation the more dramatic any cold bridging becomes
At least brings that dormer more inline with the rest of the house rather than effectively being open to the elements like it almost was before. (Rest of house is combo of new well built (but not PH), or cavity+EWI+ internal spray foam.
Still other weak points, but getting there.
Pete UK
Member
WannabeOwner
Well-Known Member
Studs, if wooden, are going to be good insulators I think?
Lintel (if spanning outer skin, cavity and inner skin) likely to be the source of bridging problem - and snots in cavities etc.
On older part of our house where we had that problem we lined the window reveals with Aerogel (very thin, for its insulation properties - not cheap, unpleasant to work with), and then MDF over the top (excuse to buy a router to make some fancy edging to make the reveal look smarter). That, coupled with MVHR, has meant that we no longer get any condensation on the windows in winter
and no sign of any mould spores etc.Knock-down-rebuild still seems to be easier than retrofit unfortunately ...
They are not bad, but hard to draft proof between all the not-quite aligning timbers with the access we had. And PIR is better, but some alternating layers then insulation plaster or tile board on top leaves just the top layer fastenings into wood as the weakest point, which isn't bad for retro fit
We covered most of these quite well with the EWI. We do have a concrete front step cover just above the lintel we couldn't do anything about, but other equivilent areas above windows etc are all under the EWI. We couldn't get Aerogel for the reveals (Wetherbe haven't signed off on this yet), but we do have 2cm of EPS on the reveals. And aerogel isn't thaaaat much better than EPS or PIR when you get down to it, you really have to be after the mm, or have a hard fail at a number to be using it I think.Lintel (if spanning outer skin, cavity and inner skin) likely to be the source of bridging problem - and snots in cavities etc.
On older part of our house where we had that problem we lined the window reveals with Aerogel (very thin, for its insulation properties - not cheap, unpleasant to work with), and then MDF over the top (excuse to buy a router to make some fancy edging to make the reveal look smarter). That, coupled with MVHR, has meant that we no longer get any condensation on the windows in winter
Coming to that conclusion TBH
. We are easily beating a standard newbuild. Probably not matching a custom passivehause newbuild, or a really posh one with MVHR built in.As part of this round we have also installed MVHR, although its not properly commissioned yet. I'm really liking it even although its untuned, probably unbalanced and not flow tested yet. Air feels better already, but some close monitoring to be done to see if it saves anything in addition to being a quality of life improvement.
Averaging about 12kw a day just now, got 18kw one early day this month when it was really clear.
250kw generated over last 30 days, saving about £100. Battery has saved another £50 through giving us cheap power during the day but also enabled fuller use of that generated power. Have only exported 1.2kw to the grid over those 30 days
.Problem is that when temp is below ~3 degrees it's about 600kw/month for heating and hot water. Insulation activities above will help address the big heat loss vector, but there are probably others to track now.
WannabeOwner
Well-Known Member
I'm really pleased to hear that, as I have not had anything to compare my own experience with. We put MVHR in old part of house after we built Passive House extension, 'coz the air quality and evenness of temperature in the new bit was just right. We weren't sure if it was a good "Spend" ... but it fixed all the condensation on windows, and any musky smell (basically mould spores). Also it spreads the heat, so the "back bedroom" that was always freezing no longer is - its not toasty, but it is a couple of degrees warmer than Artic!
People who come remark on the air quality (although they don't phrase it with those words ... but they notice that its better than their expectation).
The big thing, for me, is that the Heat Recovery isn't as good as I expected. I hadn't realised just how significant "ait tight" is in that regard. If some of the air is escaping, then that air is not being exhausted through the MVHR heat exchanger ... and the benefit of that heat, to incoming air, is missing. Unfortunately as with so much to do with Passive House, 99% isn't good enough. So the heat loss from MVHR, with a tight, but not really-really-sealed, house is significant (for heating cost, relative to potential saving lost). So stick at getting rid of your draughts
An air test once you are done will help with finding any bits that were missed.
WannabeOwner
Well-Known Member
Probably not enough cold weather left, this winter, but I think a useful test (as a baseline, against future improvements) is when you go away for the weekend turn the heating off (or down to a good 5C lower than normal) and see how fast the temperature drops (some sort of logging thermometer would help). I would expect increasing air-tightness and insulation will make a noticeable difference (and that will also be important / a factor during a summer heat wave)s. We lose between 1C - 2C if we go away for the weekend in mid winter with heating off, and in a Summer heat wave its at least 7 days before the house starts to get to uncomfortable temperatures (which we can easily solve using night-venting - and the "bypass" on MVHR will have been kicking in anyway ...)
Drew57
Active ember
That makes sense, heat escapes through canvas sides on the trailer but it should be warmer in your cab.
...sorry, I'll get my coat.
PITA
Model 3 Performance
There's another way...
I contacted GivEnergy months ago about the idea of adding extra battery storage to my existing Powerwalls...
So the Powerwalls do all the heavy lifting on the house demands... but then the GivEnergy batteries trickle feed into the system at a pre-defined discharge, like 500W (covering the house base load).
This is all possible according to them... albeit they've never been asked before and thought it was an unusual request... but yes, it is doable...
This means you'd get all the heavy discharge benefits from the Powerwall system, but the GivEnergy would cover 12 kWh per day extending the storage capability.
phil4
Member
In your model, how does the GE battery charge?
I always thought the issue with using a seperate battery with a PW was that it either saw it as solar, and drained it (to charge itself if needed), or treated it as a load and had no control over it's charging.
I guess going of what you described, it'd charge via the inverter, and so report less solar to the PW?
The other issue with the above I guess is that most (no, not all) people with a PW don't have a hybrid inverter, which sort of stymies this idea a little.
PITA
Model 3 Performance
In my conversation I asked that the GivEnergy batteries charged from Grid only, and discharged on demand up to a pre-configured discharge limit ... like 500W
At which point the Powerwalls would take over on the extra demand if needed.
They said it could be done.
phil4
Member
So you'd likely need DNO permission, since if discharging at a set time and rate, it could feed back to the grid. I'm not saying they'll say no, but they might.
But again, not sure how it would work if charging from the grid, so lets say connected at the incoming grid point, when discharging, surely the PW would then see it as "grid" and do what was needed to not use it if it felt like it.
I sound unconvinced I know... but I'm also aware I'm far from an expert and the experts you asked said they could do it. They will be right, and I'll be wrong.
guys, I wanted to ask stupid question.
I got another company phoning back to me. they were a bit surprised (right word to use?) that the ESEGroup (supplier I am looking forward to go with) were putting the following system:
5 kwh hybrid lux power inverter + 8.2 kw panel panel set + 9.6 kwh batteries.
Is it normal to have like 5 kwh inverter and 8 kwh solar? shouldn't inverter be the same/higher capacity as solar or it is good?
roof is east/west
also, how different DNO approvals on 5 kw and 8 kw inverter systems?
I got another company phoning back to me. they were a bit surprised (right word to use?) that the ESEGroup (supplier I am looking forward to go with) were putting the following system:
5 kwh hybrid lux power inverter + 8.2 kw panel panel set + 9.6 kwh batteries.
Is it normal to have like 5 kwh inverter and 8 kwh solar? shouldn't inverter be the same/higher capacity as solar or it is good?
roof is east/west
also, how different DNO approvals on 5 kw and 8 kw inverter systems?
