alt.hn

5/30/2026 at 11:08:37 AM

Show HN: Helios – what plug-in solar could generate for any address in Britain

 https://helios.southlondonscientific.com/

by ruaraidh

5/30/2026 at 1:24:01 PM

Really cool stuff. Nitpick: it failed to grab an OSM ID for my house and fell back to postcode centroid, but then still reported LIDAR-derived shading at quite high precision.

I'm wondering if it should fall back to a more general shading approach when no OSM building footprint is available, to avoid false precision? My street has a gap in the houses on the other side from mine, so picking the right location matters for the calculation.

You could also try Inspire Index polygons instead of OSM? These correspond to actual lease/freehold boundaries.

by ltrg

5/30/2026 at 1:27:19 PM

Thanks - I didn't know about Inspire Index, I'll check it out. I tend to agree about false precision. My first instinct was to use the synthetic horizon for addresses in that group, but I think that's over positive. A range might be better (if a bit more complex)?

by ruaraidh

5/30/2026 at 3:28:22 PM

> Worth it. The kit pays for itself in 7.1 years; over 20 years it's good for about £1,095 net.

This is my issue with this sort of thing. Am I going to have this kit in 7 years? Or would I upgrade to better stuff at the technology improves?

by ifh-hn

5/30/2026 at 4:33:19 PM

Why would you replace it if doing so is uneconomic?

Panel lifetime is very high. The scope for efficiency improvement is not huge (unless there is a cost breakthrough in multi band photon capture). It's not a car, phone, or computer. It's more like the rest of the house electric infrastructure.

I had my rooftop solar over 10 years ago and basically intend to leave it until some maintenance issue forces action.

(Also, the kit secondhand value is hard to determine but far from zero; 30-50% maybe?)

by pjc50

5/30/2026 at 5:30:15 PM

These calculations often fail to account for present vs future value of money.

If you’re financing the system you have no big cash outlay, but returns are further out, possibly never when accounting for the useful like of the system.

With cash up front all the returns are yours, but they are much lower than what that cash would net you in an average investment.

The financial math on small solar systems can be complex. If the system is sufficient to provide power to major appliances in a power outage (assuming you have a power outage risk in your area), it can make more sense to tie money up in these systems.

by brk

5/30/2026 at 8:10:20 PM

Notice that the pricing will come down. In Germany (where the market is mature), I can buy a 2kWp system for 500-600 EUR. Then your payback time basically halves...

by dafrie

5/30/2026 at 8:21:51 PM

To me, 7.5 years is not worth it. and the 1K in 20 years is nothing. This should be the standard and it should be free. Until then we'll keep paying through the nose for energy...

by harel

5/30/2026 at 8:50:13 PM

Maybe you guys wouldn't be paying through the nose for energy if you had more solar.

by Hamuko

5/31/2026 at 7:16:21 AM

It wouldn't be England if the sun shone.

by blitzar

5/30/2026 at 3:29:46 PM

Depends on your energy requirements and future technology and energy costs. At the moment, one should value this outlay as a fixed income equivalent investment [1].

The panels have a ~25 year warranty though [2] (at which point, they should still produce ~80% of rated output), so it’s entirely possible to just leave them in place. At a certain age (~55-60), these are the last PV panels you’ll need to buy, as they’ll potentially outlive you (assuming developed country life expectancy).

[1] https://magnifina.com/articles/rooftop-solar-yield/

[2] https://www.energysage.com/solar/solar-panel-warranties/

by toomuchtodo

5/30/2026 at 4:36:27 PM

The technology is unlikely to improve meaningfully in 7 years. And you'd only upgrade if it was a financial improvement so it makes complete sense to give an estimate based on keeping it for 20 years.

I don't see what your issue is.

by IshKebab

5/30/2026 at 11:26:26 PM

Then you are unlikely to be the person I'd be taking advice from.

by ifh-hn

5/31/2026 at 6:21:46 AM

Let me rephrase: the thing that you said clearly isn't an issue so it doesn't make sense for you to have an issue with their advice.

by IshKebab

5/30/2026 at 5:46:22 PM

I got the exact same values.

I'd like it if it would actually show me how much sun it thinks I'd get at the postcode I put in. I've got about a third of an acre of garden in a 6 acre field to play with, before I start having to dig up roads. I can afford to be quite free and easy with placement ;-)

by ErroneousBosh

5/30/2026 at 12:32:02 PM

Huh, TIL about the National LIDAR Programme: https://www.data.gov.uk/dataset/f0db0249-f17b-4036-9e65-3091...

Very interesting stuff and quite a large undertaking! I'm often impressed by the quality of the UK's open data.

by redfloatplane

5/30/2026 at 5:51:19 PM

> I'm often impressed by the quality of the UK's open data.

The ordnance survey not being open data is a bad look though.

by cowsandmilk

5/30/2026 at 7:43:00 PM

Indeed. Taillte Ireland's (Ordnance Survey Ireland's) detailed cartographic data is also not open (including historic data - maps from the 1820s and 1920s!) and it's really a huge pain in the ass. On the other hand, OSM is in pretty good shape at least for topographic information. I've used it to make hiking maps here and nobody's died - as far as I know.

As a side note, I was one of the initial developers of the Irish national open data portal. Earlier today I had Claude look for similar LIDAR data for Ireland and I saw it pull from the site I built a dozen years ago and I was unreasonably pleased with myself :)

by redfloatplane

5/30/2026 at 6:54:07 PM

I’ll add the UKHO Admiralty marine charts to this list too.

by danw1979

5/30/2026 at 1:01:02 PM

I noticed this as well! Very interesting.

by kilroy123

5/31/2026 at 11:29:18 AM

This is a nice example of making sustainability practical rather than abstract. Showing potential generation at an address level makes the decision much easier for non-experts.

A lot of climate tech needs this kind of interface: not just “this is good,” but “this is what it could mean for your specific situation.”

by syedofc

5/30/2026 at 12:21:51 PM

This is really nice! Would be great if it could handle regular rooftop solar calculations too.

by GordonS

5/30/2026 at 12:24:41 PM

Thanks! Should be doable, I just got excited by the new shiny thing first.

by ruaraidh

5/30/2026 at 5:57:37 PM

This is a really interesting project! The use of LIDAR data to account for actual building shadows is a clever approach. I'd be curious to see how this compares to commercial solar assessment tools in terms of accuracy. The UK's move to legalize plug-in solar is great for residential adoption.

by overfits_ai

5/30/2026 at 8:07:55 PM

Nice.

It would be nice to be able to pick the precise location on the map (house number appears not to work).

Also "ground floor" seems to say 1.5m off of the floor? I would like to tweak those values for e.g. panels on the floor in a garden.

by mattlondon

5/30/2026 at 2:15:53 PM

Nice. I'm working on a project called homestocompare to help people house-hunting in the UK.

Would be nice to add this as an extra data point when comparing. Are you open to collaborating at all?

by realty_geek

5/30/2026 at 2:25:15 PM

Absolutely! I have some other datasets that might be useful too (e.g. air quality). Drop me a line: ruaraidh[at]southlondonscientific.com :)

by ruaraidh

5/30/2026 at 5:09:00 PM

Great, thanks - I'll drop you a line.

by realty_geek

5/30/2026 at 2:51:12 PM

Let me know if you’d like access to alt net availability data

by simonjgreen

5/30/2026 at 5:18:26 PM

Sorry, not sure what you mean by "alt net availability"

by realty_geek

5/30/2026 at 4:18:52 PM

This is a great use of open data!

Please consider making the source code available. I’d love to make something similar for your friends across the pond (in Canada).

by dnlzro

5/30/2026 at 3:02:22 PM

Would be good to be able to select multiple points on the compass and have it tell me the best place for it (front and back garden)

by domh

5/30/2026 at 3:28:57 PM

Good idea. I want to add specific options for different mounting locations (sheds etc) as well.

by ruaraidh

5/30/2026 at 6:19:41 PM

I am just surprised about the cost?

Kits in Germany are 300€ without a battery.

by pinkgolem

5/30/2026 at 6:28:23 PM

Surprised which way? Too cheap? Too expensive? Surprised things differ in price by country?

by gib444

5/31/2026 at 5:23:46 AM

To expensive, 2x of a factor between countrys side by side is massive.

Esp. As the 300€ are more of an go to your nearest diy store and buy one, there are better deals out there.

Here is one for 239 effectively, including hanging hardware & everything you need.

https://www.mydealz.de/share-deal-from-app/2787366

by pinkgolem

5/31/2026 at 10:51:12 AM

Thanks for clarifying. Lots of vague comments here recently

We don't call it "rip off Britain" for nothing. A great many things are a rip off

by gib444

5/31/2026 at 9:32:26 AM

What are the costs of the installation based on? I haven't been able to find any for sale?

by benj111

5/30/2026 at 4:38:07 PM

What if I already have solar, can I add this?

Also do you actually need a balcony or can you hang these out of a window somehow? Very few houses in the UK have balconies.

by IshKebab

5/30/2026 at 4:53:12 PM

You can put it on the ground if you like

by jimnotgym

5/30/2026 at 3:29:01 PM

Great work. Is it possible to use this dataset to calculate total plug in solar potential within the geographic constraint?

by toomuchtodo

5/30/2026 at 4:11:38 PM

Oh, that's such a good idea! I suppose the challenge is knowing where there are installable surfaces are (or at least making defensible guesses). I'm going to have a go at this...

by ruaraidh

5/30/2026 at 5:47:55 PM

"Any address in Britain"

"Caveats: - Outside LIDAR coverage (most of Scotland and Wales) it falls back to a synthetic horizon (less accurate)"

So, "any address in the most of the southern half of Britain"?

by ErroneousBosh

5/31/2026 at 7:00:47 AM

[flagged]

by candizdar