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

My Components

Fogstar vs GivEnergy battery: Fogstar is the safer new DIY buy: GivEnergy Ltd is in administration and its administrator says further hardware warranties and support will not be honoured.
These are different battery types: Fogstar is a 15.36kWh modular rack needing a compatible inverter; the GivEnergy All in One is a 13.5kWh AC-coupled unit.
Fogstar was listed at £2,499.99 ex VAT, hardware-only, at the time of writing: but the inverter, installation, VAT and associated equipment still need pricing separately.
The GivEnergy All in One only makes sense with a written third-party remedy: identifying who will provide warranty, repairs, support and spare parts.

Updated 3 Nov 2026 Read Entry →

Energy Utilisation

Check the battery fills before the cheap window closes: the finish time is usable kWh to add divided by your charge rate, compared with the window length.
Tonight’s cost is grid import times your off-peak rate: the honest figure is the effective cost per usable kWh, your off-peak price divided by round-trip efficiency.
At 8.5p off-peak and 85% round-trip, stored energy costs about 10p per usable kWh: well under the 26.11p day rate in the example, so at this spread overnight charging pays after losses; a narrow spread may not.
Windows differ sharply: Octopus Go runs 00:30 to 05:30 (5 hours), Economy 7 gives about 7 hours, and Intelligent Octopus Go guarantees a 6-hour whole-home window from 23:30 to 05:30.
Degradation is a real cost per cycle: my Fogstar bank dropped about 10% after 800+ cycles against a 4,000-cycle rating, so a thin spread is not worth the wear.

Updated 3 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 3 Nov 2026 Read Entry →

Energy Utilisation

Installers size for annual average. Typical UK household sits at 7.4 kWh/day, pointing the formula at an 8 to 10 kWh battery.
Winter usage is +27% higher and solar drops to 29.6% of summer yield. Average sizing leaves a gap.
Extra capacity at install earns about £58/year per usable kWh on standard Octopus Go, with 5 to 7.5 year marginal payback.
Retrofit costs 30 to 50% more than the same kWh added at install.

Updated 3 Nov 2026 Read Entry →

Fundamentals

Series and parallel arithmetic explains ratings: it does not show whether a complete battery arrangement is approved.
Two hypothetical 50V, 100Ah modules store 10kWh: their 10kW figure is theoretical and the inverter can limit output.
A 48V pack can still prohibit series: Pylontech’s US5000 manual forbids series connection for US5000 and US5000-B.
Battery arithmetic cannot size protection or cables: the complete design depends on equipment, routing, ratings, and manufacturer rules.
Charge differences do not prove a wiring fix: use the exact manufacturer procedure and installer assessment.

Updated 3 Nov 2026 Read Entry →

Fundamentals

Updated 3 Nov 2026 Read Entry →

Energy Utilisation

Use the calculator to estimate your numbers based on your setup.
Real-world return: £2,729 recovered in ~2.5 years from a £9,000 DIY system.
2025 outcome: £1,668 total benefit from bill reduction, arbitrage, and export.
Payback trajectory remains attractive, with newer component pricing improving today’s economics.

Updated 3 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 3 Nov 2026 Read Entry →

Fundamentals

Home battery storage without solar pays about £730 a year on Octopus Go: a £3,300 system back in about 4.5 years modelled, nearer 5.5 to 6 in practice.
On a single-rate tariff a battery LOSES about £127 a year: there is no cheap window to charge in, so you buy at 26.11p and lose a tenth of it to round-trip losses.
Octopus Go pays 9.5p between 00:30 and 05:30: Intelligent Go is cheaper at 8p over six hours but needs a compatible EV or charger to qualify.
Plan on 80% of the modelled saving: 300 to 330 real cycles a year, not 365, and winter days that overflow a 12.9 kWh usable pack.
GivEnergy went into administration on 9 April 2026: warranties and app support will not be honoured, so route any issue through your original installer.

Updated 3 Nov 2026 Read Entry →