Section · Batteries
A battery is the most expensive single decision in the stack and the one with the slipperiest payback. Capacity matters less than the shape of your day.
In this section
Sizing
The wrong answer is "as much as you can afford". The right answer is your evening load shape.
Chemistry
If the box is on a wall in your house, the answer is almost always LFP. Here is the long-form why.
Hybrid
Tidy is not the same as reliable. What happens when one box has to do every job.
Payback
Including the bits the brochures leave out: degradation, round-trip efficiency, opportunity cost.
VPP
Octopus Tesla Energy Plan, ev.energy, others. Which ones move the needle and which are press releases.
Show your working
Long read
A 4 kWp roof in Surrey, a 5 kWh battery and a year of half-hourly meter data. We ran the numbers four different ways and changed our mind twice.
14 minute read