Standing charges mean cutting usage does not cut the bill proportionally

A bill has two components with different behaviour

Most electricity bills are built from two elements. One is a charge per unit consumed, which varies with how much you use. The other is a fixed amount levied per day regardless of consumption, commonly called a standing charge or a supply charge or a service charge depending on where you live.

The fixed component exists because a large part of the cost of supplying a household is not proportional to consumption. The cable in the street, the substation, the meter, the billing system and the obligation to keep a connection available all cost roughly the same whether the house draws a great deal or almost nothing.

The proportions vary widely between markets, and in some jurisdictions the fixed element has been shrinking while in others it has been growing. What does not vary is the arithmetic consequence, which catches people out with some regularity.

Halving usage does not halve the bill

If a bill is composed of a fixed part and a variable part, then reducing consumption only acts on the variable part. Halve the units and you halve one component while the other sits unchanged, so the total falls by less than half.

That is worth taking seriously when assessing the value of an efficiency measure or a solar array, because savings are routinely presented as a percentage of the whole bill. A measure that genuinely eliminates a quarter of consumption will not reduce the total by a quarter, and the discrepancy grows as the fixed component grows.

It also explains something that puzzles new solar owners: a household generating a great deal of its own electricity can still receive a bill that feels stubbornly large. The generation is doing exactly what it should. The fixed charge is simply not something generation can touch.

Why the structure is contested

This is one of the genuinely disputed areas of energy pricing and it is worth representing the disagreement rather than resolving it. A high fixed charge recovers network costs from the people who impose them, which is defensible, and it falls hardest on low-consuming households, which is regressive in effect if not in intent.

A low fixed charge with everything loaded onto the unit rate rewards reducing consumption, which is generally what energy policy says it wants. It also means that households which reduce consumption sharply — by generating their own, most obviously — stop contributing to network costs they still rely on, which shifts those costs onto everybody else.

Both arguments are serious and neither is obviously right. Different jurisdictions have landed in different places and several have reversed direction. Anyone reading a strong opinion on this should notice which of the two effects the writer has decided to care about.

What it means for judging a solar quote

When a proposal expresses savings as a percentage of your current bill, the first question is whether that percentage is calculated against the whole bill or against the variable part. Only the variable part is addressable, so a saving quoted against the total is describing something that cannot happen.

The more robust way to assess any generation or efficiency measure is in units rather than currency. How many kilowatt-hours does this avoid importing? Multiply by the unit rate to get the saving, and leave the fixed charge out of the calculation entirely because nothing you install will change it.

Doing it that way has a second advantage: unit savings are stable while prices are not. A measure that avoids a certain number of units each year keeps avoiding them when rates move, and the currency figure can be recalculated whenever it matters.

The one case where the fixed charge disappears

There is a way to stop paying a standing charge, and it is to remove the connection altogether. Disconnecting from the grid ends the fixed charge along with the ability to import anything, and that is a very poor trade for almost every household in almost every climate.

Going off-grid means sizing generation and storage for the worst stretch of the year, not the average, and in a cloudy winter at high latitude that means an installation several times larger than one designed to work alongside a connection. The grid is, in effect, an infinitely large battery with perfect availability, and the standing charge is the rental on it.

Seen that way, the fixed charge is buying something. Whether it is priced fairly is a legitimate argument, and it varies by market and by regulator. But a bill that does not fall to zero when a household generates most of its own electricity is not evidence of anything going wrong. It is the connection being charged for separately from the energy.