Solar Basics
Why the optimum tilt for an array is flatter than people expect
The old rule of setting tilt equal to latitude optimises for one moment in the year, and annual energy…
· 4 min read
Daniel Okonkwo
Editor, Power Your Roof
Daniel writes the explanatory pieces on solar basics, batteries, bills & tariffs and is unreasonably interested in the detail nobody else checks.
26 articles
Solar Basics
A shadow on one corner costs far more than one corner
Cells wired in series must all carry the same current, so the darkest cell sets the limit for everything…
· 4 min read
Solar Basics
Optimisers and microinverters fix different halves of the same problem
Both put electronics under every panel and both are sold as a shading remedy, but they split the work…
· 4 min read
Batteries
What a cycle counts, and why warranties measure it two ways
A warranty may be expressed in years, in cycles or in total energy delivered, and which of those three…
· 4 min read
Bills & Tariffs
An east and west array can beat a south-facing one on the bill
Splitting panels across two opposite slopes gives up some annual generation and returns a production curve…
· 4 min read
Installation
The inverter is the part most likely to fail first
It performs the most complex job in the system, contains the components with the shortest service life, and…
· 4 min read
Solar Basics
What a panel is actually rated to survive: hail, snow and mechanical load
Modules are tested against defined impacts and defined pressures, and knowing what those tests represent…
· 4 min read
Batteries
Where the battery physically goes changes how long it lasts
Temperature governs the ageing rate of every cell, so the difference between a loft and an unheated garage…
· 4 min read
Batteries
The percentage on the app is an estimate, and estimates drift
No battery has a fuel gauge, so the state of charge you are shown is calculated, and knowing how it is…
· 4 min read
Bills & Tariffs
An electric car is the largest load most houses have ever had
Charging adds an annual consumption comparable to everything else the household uses, and the way it…
· 4 min read
Bills & Tariffs
A heat pump changes the shape of a bill, not only its size
Replacing a fuel with electricity moves a household’s largest load onto the meter, and whether that helps…
· 4 min read
Installation
Export limitation is how a large array fits a constrained connection
Where the local network cannot accept full output, an inverter can be told to throttle what it sends out…
· 4 min read
Efficiency
Replacing windows is among the least rewarding energy measures
Glazing is expensive per square metre and windows are a modest share of a building’s surface, so the energy…
· 4 min read
Efficiency
Lighting stopped being a large number, and the advice has not caught up
The change from filament to solid-state lighting was close to an order of magnitude, which quietly demoted…
· 4 min read
Solar Basics
What moves in underneath a solar array
The gap between panels and tiles is sheltered, warm and inaccessible, which makes it attractive to birds…
· 4 min read
Batteries
A battery ages while it sits, not only while it works
Calendar ageing runs in parallel with cycle ageing, which means an underused battery still loses capacity…
· 4 min read
Bills & Tariffs
Who actually owns the array on the roof
Some residential systems belong to a third party under a long lease of the roof, and that arrangement…
· 4 min read
Bills & Tariffs
An estimated bill is a forecast, and the correction always arrives
When no meter reading has been taken, the figure on the bill is a model of your consumption, and the…
· 4 min read
Bills & Tariffs
Measuring your own consumption without fooling yourself
Clamp meters, plug monitors and inverter apps all measure something slightly different, and the…
· 4 min read
Efficiency
Getting the water out of laundry costs more than heating it did
Evaporating water takes several times the energy of warming it, which is why the spin cycle matters more…
· 4 min read
Solar Basics
Cell technology matters less on a domestic roof than the datasheet suggests
The industry has moved through several cell architectures in a decade, and only two or three of the…
· 4 min read
Solar Basics
A solar thermal collector and a photovoltaic panel want the same roof
Heating water directly with sunlight is more efficient per square metre than making electricity, and that…
· 4 min read
Solar Basics
Where the annual yield figure in a quotation comes from
A predicted generation number is a model output built from historical weather, a geometric shading…
· 4 min read
Solar Basics
What happens to a solar panel when it finally comes off the roof
A module is mostly glass and aluminium wrapped around a small quantity of silicon, and the difficulty of…
· 3 min read
Batteries
Coupling a battery on the direct-current side is a different machine
A battery can join a solar system before the inverter or after it, and the choice decides how many…
· 4 min read
Bills & Tariffs
A block of flats is the hardest place to share a solar roof
One array, one roof and many meters is a problem of allocation rather than engineering, and the difficulty…
· 4 min read