Solar Energy Concepts

DIY Solar for UK Homes. Real guides from a real install.

Step-by-step practical guides, component lessons, and hard-earned fixes from a real UK DIY solar setup.

7.15kWpinstalled 6,072kWhgenerated 2025 £1,668/yrmodelled value

Latest field notes

Fundamentals

Octopus Nook is a plug-in home battery range: the 2 kWh Cube needs no installer, the Colossus stacks to 30 kWh; Octopus says the Cube is due in Q1 2027; no price or month announced as of 11 November 2026.
Compared with hardwired, DIY rack and Powerwall options: the Cube is the only announced plug-in path; capacity, install and backup differ sharply.
Charging from a socket is legal today; the Cube’s discharge method is not disclosed: a battery draws power out of a socket like any appliance, but Octopus has not said how the Cube feeds power back, so the full method cannot be checked yet. Plug-in solar, which pushes generation into a socket, became legal in Great Britain on 27 August 2026 for kits listed Compliant on the ENA register.
The “two or three years” payback is a launch claim, not a fact: a fully cycled Cube saves £100 to £120 a year depending on your tariff, implying a £200 to £360 price that no finished battery currently sells for.
2 kWh covers an evening baseload, not a home: about 1.3 to 2 hours at a typical 1 to 1.5 kW evening baseload, which is why the Cube stacks to 10.5 kWh.
Price, full specs, and the launch month are still unannounced: Octopus has given no price for either model and no month for the Cube, and it has not said who builds the Nook hardware.

Updated 12 Nov 2026 Read Entry →

My Components

After 3 years, my Fogstar packs report 87.5Ah to 89.3Ah of a rated 100Ah: about 0.018Ah lost for each counted cycle.
The three packs share the work evenly: since September 2024, each counted 367 to 372 cycles and lost 6.7Ah to 6.8Ah.
The pack that worked alone for a year is 1.7Ah behind: it arrived with about 95 extra cycles, and the gap has not grown since.
Octopus Go and Solar Assistant automation saved £1,668 in 2025: my exact charge settings are in the article.
Uneven charge readings came back together: a BMS firmware update and an overnight discharge limit fixed them in my system.

Updated 8 Nov 2026 Read Entry →

Fundamentals

Home batteries lose about 2 to 3% of capacity a year: a study of 21 German home batteries measured 2.2% a year for LFP. My three packs show 3.3% a year on their screens.
After 3.5 years my packs show 87 to 89 Ah of a rated 100 Ah: fourteen readings from three packs sit on one straight line against the cycle count.
The capacity on a battery screen is an estimate: at the same 52.4 V, my three packs showed 39%, 40% and 50% charge. Read the screen as a trend.
Read battery life in years, not cycles: at my pace, 4,000 cycles take 22 years, but my screens reach 80% in about six years.
My battery does more work every winter: its winter output grew from 6.1 to 10.2 kWh a day in three winters.
Buy about double the storage you think you need: wear and a 20% reserve both take a slice, and home use keeps growing.

Updated 8 Nov 2026 Read Entry →

Practical and DIY

Adding another solar battery needs an exact compatibility check. Matching voltage or brand is not enough.
A matching communication socket does not prove compatibility. The equipment must support the intended control arrangement.
Mixed ages and capacities depend on the product rules. Manufacturer permissions differ between configurations.
Similar charge readings do not establish pack compatibility. Cell balancing and bank expansion need separate checks.
Get the supported expansion and complete quote before buying. Include commissioning and warranty responsibility.

Updated 8 Nov 2026 Read Entry →

Fundamentals

Most UK homes need 5 to 10 kWh of battery storage: your daily use and how much you shift off peak decide the number, not your roof.
AC-coupled or DC-coupled decides what you can retrofit: AC-coupled bolts onto solar that already works and loses 10-15% round trip; DC-coupled is 95-97% efficient but needs a hybrid inverter.
Only one UK brand publishes a checkable price: Fogstar Energy at £109-121 per usable kWh (24 July 2026), against roughly £700-780 per kWh for an installed all-in-one. Everything between is inferred.
Check the C-rate before the capacity: a 5 kWh battery at 0.5C delivers 2.5 kW, which runs lights and a fridge but not an oven.
GivEnergy went into administration on 9 April 2026: warranties and app support are not being honoured, so treat any remaining stock as unwarranted.
The whole case is one spread: 26.11p/kWh to buy against 12p at best to export, so every stored kWh is worth the difference.

Updated 8 Nov 2026 Read Entry →

Fundamentals

Use the calculator below to compare tilt, direction and 10-year ROI for your roof. It covers every UK region; the optimal angle barely changes across a postcode area.
The textbook optimum is 35-40° facing south, but east-west and even vertical setups beat it for many real households.
Flat roofs win summer, steep walls win winter. Match the angle to when you actually use power.

Updated 7 Nov 2026 Read Entry →

System Guides

East/west roofs lose about 19% of annual yield vs south, but the demand-curve match is often better for a typical 3-bed household.
A battery turns the midday lull into evening savings. The single biggest ROI lever on this roof.
The budget 3.6kW DIY build is £2,400 and pays back in 3.3 years on a typical 3-bed.
The premium 5kW + 16kWh build only makes sense with a heat pump or EV.

Updated 7 Nov 2026 Read Entry →

Practical and DIY

Honest verdict: a solar gazebo is expansion with garden value, not a free lunch on yield per panel.
My build: about £2,018 including tools for 3.28 kWp on a ~6° flat roof structure.
Flatter tilt means more panels and more cleaning where water ponds on the frame edge.
Compare roof and ground first if height safety and planning allow a better tilt.

Updated 7 Nov 2026 Read Entry →

System Guides

UK solar panel output is strongly seasonal: June and July normally peak, while December produces the least.
Winter output is a small part of summer output: November to February cannot be treated like four average months.
A battery cannot move summer electricity into winter: size it around daily surplus, not annual generation.
PVGIS provides the useful estimate: enter your location, roof direction, angle and system size rather than relying on one UK average.

Updated 7 Nov 2026 Read Entry →