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Sharing some (simplified!) illustrations re home heating: N home thermal energy *need* U actual thermal energy *use* C resulting energy *consumption* N = a function of climate & building fabric ("fabric efficiency") U → C function of technological efficiency (here, a gas boiler)

Actual thermal energy *use* (U) is a function of *both* - need (N) - & the effective *cost* of thermal energy consumption (C). Hence, 2 arrows converge: N → U ← C ← cost

Gas boiler vs heat pump 85% = av. total in-home gas inefficiencies in UK SCOP = "seasonal coefficient of performance" = effective efficiency over a year, for a given unit, in a given place (varies by climate).

Note that here I'm focusing only on what happens around end-use consumption. Not looking at (often v. large) upstream system energy (in)efficiencies / energy loss. Note these are arbitrary units, illustrational only - but pegged to the "baseline" gas boiler / central heating efficiency.

Here thinking about the different possible relationships between Need (N) & Use (U). N = U Sufficiency N > U Insufficiency N < U Over-sufficiency (profligacy?) N = U Sufficiency As above, N = function of climate & building fabric ("fabric efficiency"). Retrofit / insulate to reduce N.

To do: Remake the above as Sankey diagrams, showing heat/energy loss at each stage (including upstream of the home); & showing heat (or coolth) *transferred* by a HP. Would look something like these nice diagrams by @janrosenow.bsky.social, but with added "need" variable. bsky.app/profile/janr...