Glossary

The product of voltage and current, which is what an inverter is actually rated to deliver. Always equal to or larger than the real power in kW.

kVA = kW ÷ PF

Essential, Important or Comfort. Deciding which tier stays on during an outage is the single biggest lever on cost.

How long the system must keep the chosen loads running with no grid. Together with the load split, this is what sets the battery size.

The currency product prices are stored in. Everything shown to a user is converted from it at the stored rate.

Continuous discharge power as a fraction of capacity. A 10 kWh pack at 0.5C delivers 5 kW. A short, heavy backup need is limited by C-rate, not by kWh.

kW = kWh × C-rate

The realistic maximum the supply must carry at one instant, after demand and diversity factors are applied. This is what the inverter must serve.

Σ demand W × diversity

The sum of the nameplate ratings of everything you have selected. Nothing ever draws all of it at once.

Σ (quantity × rated W)

PV array kWp divided by inverter AC kW. Ratios of 1.1 to 1.4 are normal; higher ratios clip the midday peak but raise total yield.

kWp ÷ kW

The share of an individual load that counts toward the coincident peak. A microwave used for ten minutes has a low demand factor; a fridge has a high one.

How much of a battery's nameplate capacity may be used. Lithium iron phosphate packs commonly allow 90-95 %.

usable = nominal × DoD

A factor below 1.0 recognising that not every appliance runs at the same second. It falls as the number of load lines rises, and is never allowed to take the peak below the largest single load.

The fraction of its "on" time that an appliance actually draws power. A fridge is on for 24 hours but its compressor runs about a third of that.

The process of vetting and registering an installer or EPC contractor as an approved partner, with their documents and capabilities on file.

Engineering, Procurement and Construction - a firm that takes a project from design through supply to a commissioned system.

A single unit that manages PV input, battery charge and discharge, the grid connection and a backup output for the essential circuits.

The rated DC output of a PV array under standard test conditions. Sizing is always quoted in kWp.

The number of hours per day of 1000 W/m² equivalent sunshine. A 5 PSH site gives a 1 kWp array about 5 kWh of DC energy a day before losses.

yield = kWp × PSH × derate

Where an enquiry sits in the sales process, from new enquiry through to won or lost. Each stage carries a colour code and a probability.

The ratio of real power (kW) to apparent power (kVA). Motors run at a lower power factor than heaters and electronics, so they need more kVA for the same kW.

PF = kW ÷ kVA

Capacity deliberately held back and never planned into the backup window, so the pack is not run flat.

Energy you get back out of a battery divided by the energy put in. Typically 92-96 % for lithium.

The supply arrangement. Homes are usually single phase at 230 V; larger offices are often three phase at 400 V. The inverter must match.

The share of a day's total consumption the array is sized to cover. 100 % means a full day's energy on an average day.

The brief spike a motor draws while starting - typically three to four times its running power for a fraction of a second. It frequently sets the inverter size.

rated W × surge factor

The combined allowance for soiling, temperature, mismatch, wiring and inverter losses. Typically 0.75-0.85.

What you can actually take out of the pack, after depth of discharge, the reserve and the end-of-warranty ageing allowance.