Solar Panels

[Grumble]

This thread is now a year old.

Has anyone rerun the numbers recently, given electricity prices gave gone up a smidgen? Must mean solar + battery is more appealing?

I'm assuming arranging an installation now will mean a wait of a year or something, though, given the funded up state of this country.

Battery on its own is pretty appealing tbh, solar is a boost to that rather than the other way around of battery being a boost to solar.

[Imrael]

I havent done the numbers on ours, but the biggest single saving is probably much lower EV mileage costs. Public charging prices have gone up a lot (not un-naturally) so a charge thats either entirely from battery or off-peak supplemented by it is a big plus.

Recently the ability to ignore short power cuts has also been useful, although I dont really believe the doom-and-gloom about a winter of rolling cuts so I largely discard that beyond a little bit of "smug mode".

Its hard to be sure about effect on electricity use because we've done a bunch of other changes at the same time, but we were net explorters for several months over summer and still seem to have lower bills. Doubtless the payback time is well beyond my probable lifespan, but it should feed through into eventual house sale value. And I'm willing to expend capital for lower running costs at this point in my life.

[TopBadger]

Yesterday I ran the online simulator to see what the numbers would look like for my place. Lots of sun and a conveniently oriented and angled roof.

Results were that the payback period is estimated to be 39 years and I'd need planning permission.

Not overly tempted to go ahead, I must say.

What simulator did you use?

Energy saving trust solar calculator suggests I'd get a net lifetime benefit of £8k (and we do plan to stay where we are for the next 25 years and live in the sunny south, SSW roof and no shading at all) and thats without putting in a battery which allows using more of what is generated rather than making 5p for each kwh sold back to the grid. Apparently a 6kPw system is expected to generate 5,158kWh/year - which is more than I use a year, hence with a suitable battery we might be able to live off grid for perhaps 9 months of the year (in the winter I'd expect we'd use more than we could generate and store).

[shpalman]

The bills at my parents' house went from the joint account but the money feeding in from the solar panels went to my dad's account - then when my dad died they started being such whiny passive aggressive c.nts about putting my mum's name on the cheque, as if they wouldn't send the thugs around after ten minutes if you hadn't paid your gas bill, that they can get to f.ck the lot of them.

[lpm]

Yesterday I ran the online simulator to see what the numbers would look like for my place. Lots of sun and a conveniently oriented and angled roof.

Results were that the payback period is estimated to be 39 years and I'd need planning permission.

Not overly tempted to go ahead, I must say.

What simulator did you use?

Energy saving trust solar calculator suggests I'd get a net lifetime benefit of £8k (and we do plan to stay where we are for the next 25 years and live in the sunny south, SSW roof and no shading at all) and thats without putting in a battery which allows using more of what is generated rather than making 5p for each kwh sold back to the grid. Apparently a 6kPw system is expected to generate 5,158kWh/year - which is more than I use a year, hence with a suitable battery we might be able to live off grid for perhaps 9 months of the year (in the winter I'd expect we'd use more than we could generate and store).

A very quick look at the calculation show they assume you save self-used kwh at the 30p current day time cap. But with a battery you'd be shifting some of that saving to the night rate, reducing the solar saving.

Which suggests Grumble is right again, battery is more attractive.

However the current price cap of 30p is actually made up of 47p real cost and 17p fossil fuel govt subsidy. In April 2023 hopefully they'll axe the subsidy and middle/rich deciles will be paying the full whack.

[El Pollo Diablo]

Fwiw after a chat with my mum last night, it turns out the government energy subsidy has put her into profit - the £66 per month is more than the £40 per month she's using (she lives in a retirement flat, so gets a lot of residual heat from her neighbours).

[dyqik]

This thread is now a year old.

Has anyone rerun the numbers recently, given electricity prices gave gone up a smidgen? Must mean solar + battery is more appealing?

I'm assuming arranging an installation now will mean a wait of a year or something, though, given the funded up state of this country.

Battery on its own is pretty appealing tbh, solar is a boost to that rather than the other way around of battery being a boost to solar.

Although there you are essentially investing in the continued price disparity between daytime and nighttime electricity, rather than in any particular physical efficiency or energy savings (modulo the efficiencies associated with running a more constant baseload on the grid). That price disparity is a mostly artificial thing that could go away before the payback time of the battery. My electricity costs the same all around the clock.

Whereas with solar panels, you are investing in direct reduction in the amount of electricity you are receiving from the grid.

[lpm]

The day/night disparity has to last a couple decades, surely? We're building more offshore wind faster than nighttime-using EVs are entering the UK fleet.

[Grumble]

This thread is now a year old.

Has anyone rerun the numbers recently, given electricity prices gave gone up a smidgen? Must mean solar + battery is more appealing?

I'm assuming arranging an installation now will mean a wait of a year or something, though, given the funded up state of this country.

Battery on its own is pretty appealing tbh, solar is a boost to that rather than the other way around of battery being a boost to solar.

Although there you are essentially investing in the continued price disparity between daytime and nighttime electricity, rather than in any particular physical efficiency or energy savings (modulo the efficiencies associated with running a more constant baseload on the grid). That price disparity is a mostly artificial thing that could go away before the payback time of the battery. My electricity costs the same all around the clock.

Whereas with solar panels, you are investing in direct reduction in the amount of electricity you are receiving from the grid.

Yes and no, if anything if operators want to promote demand response then price signals will get stronger not weaker.

[TopBadger]

Battery also assumes you have an Eco 7 capable meter... I have a smart meter so I'd hope it is eco 7 capable but it's not trivial to find out

[Matatouille]

The day/night disparity has to last a couple decades, surely? We're building more offshore wind faster than nighttime-using EVs are entering the UK fleet.

Depends how cheap megascale batteries get. If I was an owner/operator of a wind farm, which generates approximately the same all hours of the day, I'd like to buy a big battery to put my wind juice into in the oversupply/cheap hours, and defer selling it into the grid until the higher demand and higher price times. If the economics stack up it'll happen. As you say, there will need to be a £/kWh variation through the day for industrial generators as long as disparities of supply/demand exist through the day. Regardless whether cost to consumers is artificially flattened (i doubt it), there is still a day/night price disparity to capitalise on but the ability to benefit from it will shift higher up the food chain.

[dyqik]

The day/night disparity has to last a couple decades, surely? We're building more offshore wind faster than nighttime-using EVs are entering the UK fleet.

Depends how cheap megascale batteries get. If I was an owner/operator of a wind farm, which generates approximately the same all hours of the day, I'd like to buy a big battery to put my wind juice into in the oversupply/cheap hours, and defer selling it into the grid until the higher demand and higher price times. If the economics stack up it'll happen. As you say, there will need to be a £/kWh variation through the day for industrial generators as long as disparities of supply/demand exist through the day. Regardless whether cost to consumers is artificially flattened (i doubt it), there is still a day/night price disparity to capitalise on but the ability to benefit from it will shift higher up the food chain.

It also depends on how cheap home and workplace scale batteries get (including EVs charging overnight), as a large increase in the number of those will flatten demand. I could imagine workplaces with high variability between day and night use installing a container of batteries in the parking lot to store cheap nighttime electricity for use in the day, and also to act as power backup for outages.

[lpm]

Current energy prices per kWh:

Electricity: Night 12.0p / Day 43.4p (Octopus Go)
or
Flat rate 34p

Gas 10.3p

Without the fossil fuel subsidy it would have been:

Electricity: Night 29p / Day 60p
or
Flat rate 52p

Gas 14.8p

Cornwall Insight forecast April 2023 prices to be in the region of 60p electricity and 18p gas. But then a bit lower in July/Oct 2023.

I think that Energy Saving Trust solar calculator is failing to do its job. It's a bit pointless to run cost/benefit on current subsidised prices when we know anyone who can afford to invest in solar is not going to be subsidised much longer. For me it said:

Generate 3,112 kwh p.a. (£7,900 installation cost)

- 1,392 kwh self-used during day saving £473 at 34p
- 1,720 kwh sold to grid saving £86 at 5p
- total saved £559 p.a.
- payback 14 years

Run the calculation at current unsubsidised rates, assuming no battery storage:

- 1,392 kwh self-used during day saving £724 at 52p
- 1,720 kwh sold to grid saving £86 at 5p
- total £810 p.a.
- payback 10 years

Assuming battery storage at 80% success with a 20% spill to the grid, and nighttime purchasing only replaced:

- 2,490 kwh self-used night rate of 29p saving £722
- 622 kwh sold to grid saving £31 at 5p
- total £753 p.a.
- payback 10.5 years

Not sure how to consider the battery cost. Having an EV means a pre-existing battery to soak up generation, and most people considering solar will be buying an EV in the 25 lifespan horizon. There's also clever things you can do with hot water tanks, to act as a thermal storage semi-battery.

Anything I'm missing on this?

[bolo]

If battery prices drop a lot, the price differential between day and night will surely also drop?

[lpm]

Ripple 3 looks to be doing very nicely in terms of people reserving.

Incredible - we've just hit 16,000 reservations for Project 3

That's almost 3x bigger than Kirk Hill and over 15x bigger than Graig Fatha.

We're so excited for this one. It's going to be huge.

They've implied there will be two projects in 2023, one solar and one wind.

I need a top up, I underestimated my car usage a year ago and have switched hot water from gas to electricity. Would be fun to watch a solar farm being built. A £25 reservation can be applied to either.

[Grumble]

Ripple 3 looks to be doing very nicely in terms of people reserving.

Incredible - we've just hit 16,000 reservations for Project 3

That's almost 3x bigger than Kirk Hill and over 15x bigger than Graig Fatha.

We're so excited for this one. It's going to be huge.

They've implied there will be two projects in 2023, one solar and one wind.

I need a top up, I underestimated my car usage a year ago and have switched hot water from gas to electricity. Would be fun to watch a solar farm being built. A £25 reservation can be applied to either.

The model makes so much sense. Had my sister asking me about it recently. I expect my electricity usage to go up a lot when I get around to getting an EV, but purchase price is still a barrier to entry.

[bjn]

Still waiting for Kirk Hill to be done. When out boiler finally dies and we flip to a heat pump I’ll probably have to top up.

[lpm]

How long do gas boilers last? 20 years?

I've just checked and mine was 2009. So maybe I'll get the excitement financial misery no, let's go with excitement, of heat pumps sooner rather than later.

[Grumble]

Still waiting for Kirk Hill to be done. When out boiler finally dies and we flip to a heat pump I’ll probably have to top up.

You might need to plan it before it dies, normally if it dies you need replacement ASAP and heat pump install might take longer to arrange.

[TopBadger]

You've probably read that heat pumps are massively subsidized right now... £3k down from £8k... so not a bad time to make the switch if a switch is to be made.

[IvanV]

You've probably read that heat pumps are massively subsidized right now... £3k down from £8k... so not a bad time to make the switch if a switch is to be made.

In terms of the capital cost. But electricity still costs something like 4 times the cost of gas. That's a better ratio for heat pump than the 5 times it was not very long ago. But it is still a bit higher than the 3.3 ratio, which is the point generally reckoned to be where a heat pump becomes about the same cost to run, in terms of operating costs, as a gas system. Though you would probably need to run the heat pump at night to some degree, given it doesn't heat up the house anything like as fast a gas. And so you could use a time-of-day tariff for your electricity, which might save you a bit, if you were clever about when you did and didn't run it.

I was surprised to discover a couple of my friends installing heat pumps just to be virtuous. I hadn't expected it of them.

It's been very slow dealing with this solar panel installer arranged by through the council. I think it is now about 9 months since I kicked off the process. At that time, I was umming and aahing about whether I'd have a battery or a diverter to heat my water instead, but now I feel having a battery is a no-brainer.

The complication is that the installer reckons that the shape of my sloping roof is sufficiently unfriendly, that they can only put about 4 on the sloping parts of my roof, the rest would go on my flat roof. That immediately got me thinking about how that would work when I need to replace the roofing felt, which is about a 15-year life, whereas the panel system is a 20 year life and probably longer. It turns out that modern panel systems for flat roofs they make no holes, it is held down by gravity - they put bags of gravel inside the frames to weight it down. So it seems I could take it all apart when I need to have the roof refelted, which is coming up in about 5 years, and put it back together again. It also seems that it won't be difficult to put the batteries in my "loft", even though I have no normal loft, just these little voids under the eaves, most of my roofspace being occupied by rooms. The battery is a lot more compact than I expected. Clearly car batteries have to be very compact, but you expect household storage batteries to be not so compact as normally they wouldn't need to be. Maybe they are selling me a more compact, small one, precisely because of the location difficulties in my house.

[lpm]

You'd be incredibly lucky to get an install for £3,000 (i.e. £8,000 less £5,000 government subsidy).

It could easily be £7,000 or £8,000 (i.e. £12,000 to £13,000).

Gas boilers are forgiving of a bad install - they can churn out the heat anyway and the inefficiencies didn't matter much when gas was keep. Heat pumps need a top quality install, otherwise inefficiencies of running costs will be magnified.

This means careful heat loss calculations, review of radiator size and positioning, potentially replacing microbore radiator piping. Air-to-air heat pumps might be a better answer if radiators are going to be an expensive replacement project. And insulation needs to be as good as possible before you even start.

It's more like when people first installed central heating - big expensive change to the house for a long term solution.

My understanding of the £5,000 government subsidy (or £6,000 for ground source heat pump, which you'd only pay for if you lived in a very large house) is:

- when getting rid of a fossil fuel boiler only
- must have valid EPC with no outstanding recommendations like loft and cavity wall insulation
- someone said it was unavailable for air-to-air, someone else said you could get it for A2A

[TopBadger]

My Solar + Battery is being installed next week - I'm looking forward to see how it goes in terms of generation...

[lpm]

In terms of the capital cost. But electricity still costs something like 4 times the cost of gas. That's a better ratio for heat pump than the 5 times it was not very long ago. But it is still a bit higher than the 3.3 ratio, which is the point generally reckoned to be where a heat pump becomes about the same cost to run, in terms of operating costs, as a gas system

Electricity is currently 3.4x the cost of gas. So a COP of 340% is the basic target. Actually a bit easier, 290% say, because of the inefficiency of gas boilers running at about 85%.

Even a poorly installed system will beat that. There's a seasonal version of COP, SCOP, which takes into account the low percentage during very cold spells offset by high percentages during mild winter weather - you can plug your house's location into a calculator and it uses average weather data.

But, as you imply, matching running costs isn't enough to give a payback on the initial outlay. I think lucky people with a perfect system with low upfront costs will eventually payback the cost, but it takes a fair while. For most people the upfront cost is pure expense. Without the government grant it would be an impossible sell.

[lpm]

My Solar + Battery is being installed next week - I'm looking forward to see how it goes in terms of generation...

It would be interesting to hear how the experience goes, with all the hassle of install and new wiring etc, as well as approximate prices and sizes?