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Solcast thoughts.....

Solar Photovoltaic (PV)

Last Post by Majordennisbloodnok 5 days ago

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TechnoGeek

(@technogeek)

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Topic starter 12/12/2025 9:16 am

I have just had a new solar array and batteries installed in the last week and have the option to sign up to Solcast for my PV array.

Does anybody use their service and what are your thoughts? Any good, is it worth it?

I believe they do a free account for home owners with limited features but are these features enough to get the best out of your PV array?

Regards

5 Bedroom House in Cambridgeshire, double glazing, 300mm loft insulation and cavity wall insulation
Design temperature 21C @ OAT -2C = 10.2Kw heat loss, deltaT = 8 degrees
Bivalent system containing:
12Kw Samsung High Temperature Quiet (Gen 6) heat pump
26Kw Grant Blue Flame Oil Boiler
4.1Kw Solar Panel Array
34Kwh GivEnergy Stackable Battery System

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Majordennisbloodnok

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12/12/2025 3:43 pm

Of the various solar PV forecasting services, Solcast seems to have been found to be the most accurate. However, whether it’s worth using is a hugely different matter. Do you have any idea of how you want to use it?

Solcast is also closely linked with the Home Assistant addon called Predbat (or Batpred). I looked into this and decided what it provides does make a financial difference, but I get almost the same benefit from a couple of basic Home Assistant automations that fill the battery enough to tide over the Agile expensive times, and that doesn’t need any forecasting at all.

For me and my situation, any forecast costing more than zero pence is too expensive.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"

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TechnoGeek

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Topic starter 12/12/2025 4:59 pm

@majordennisbloodnok thanks for your thoughts.

My initial strategy is to fill the batteries with cheap power overnight during Winter but leave enough space in the batteries overnight before a day of solar availability. Summer time it is a little easier to predict I think plus I only need to ensure the batteries are a 1/3 full in summer as the heat pump will be off so a lot more flexibility regarding solar charge.

Regards

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Majordennisbloodnok

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12/12/2025 5:21 pm

Understood, @technogeek. I can’t remember; do you use Home Assistant or not?

"Semper in excretia; sumus solum profundum variat"

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TechnoGeek

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Topic starter 12/12/2025 5:49 pm

@majordennisbloodnok

Posted by: @majordennisbloodnok

↑

do you use Home Assistant or not?

No I do not. It seems the GivEnergy portal can speak directly to the Solcast API so Home Assistant in this case, may not be needed.

Regards

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Majordennisbloodnok

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12/12/2025 6:00 pm

In that case, @technogeek, I’d sign up for the free solcast account and see how you get on with it. Alternatively, play about with scheduling to a 65% state of charge overnight and see how well it works without any forecast at all.

"Semper in excretia; sumus solum profundum variat"

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TechnoGeek

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Topic starter 14/12/2025 3:25 pm

@majordennisbloodnok I have decided to take the plunge.

Added my electricity account access to my system so it could get tariff pricing at various parts of the day and added the Solcast account. It appears the GivEnergy system then takes over the day to day battery management.

It looks like it uses algorithms to analyse your previous usage and the predicted solar forecast to decide how much power to import ( in my case ) overnight and leave enough capacity for solar charging.

Will let it run for a couple of weeks after I have got the loss factor correctly set and report back on how I got on with it. It looks promising on first impressions.

Regards

👍

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TechnoGeek

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Topic starter 11/01/2026 12:52 pm

@majordennisbloodnok it has been a few weeks since adding the Solcast portal so reporting back as promised.

After correctly setting the PV array azimuth and incline together with the system loss information in the Solcast model, I am pleased to conclude the Solcast forecasts are very accurate 🙂 and well worth using.

As an example, over the last 3 days it was estimated I would generate 6.23Kwh. My actual generation was 6Kwh

Solcast provide an API to enable someone to put a program together if their respective solar system / battery management software does not provide for integration to Solcast.

Regards

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Majordennisbloodnok

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11/01/2026 1:17 pm

Thanks, @technogeek. Good to hear about the accuracy.

Currently, the only way I know of fully integrating Solcast into any automated charging using Home Assistant as the hub is by installing an addon called Predbat (aka Batpred). It’d be interesting to find out what other alternatives there may be to compare against.

"Semper in excretia; sumus solum profundum variat"

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