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This 1992 book suggests that volume metering (ie, simply measuring and charging based the volume of hot water delivered to an end-user) may be superior to energy metering (ie, measuring the actual amount of heat delivered) for geothermal district heat systems. Wikipedia makes a similar suggestion, generalized to all district heat systems, but doesn't offer a citation for it. In both cases, the argument seems to be that energy or heat measuring is more complicated, expensive, and error prone, and that volume metering has the added benefit of incentivizing the end-user to more efficiently extract heat from the hot water they receive.

However, my impressions is that energy metering is much more common than simple volume metering. The 1992 book mentions that the majority of geothermal systems use energy metering, and more modern sources seem to take for granted that heat meters are integral components of any district heating system.

The above two sources are the only ones I can find that actively compare the tradeoffs of volume versus energy metering, and obviously neither is particularly detailed, authoritative, or up to date. My impression is that energy metering is generally preferred for modern systems, yet I cannot find any good sources that explicitly argue for this preference.

What are the advantages of energy metering over volume metering for district heat systems? At this point, is there a clear preference, or are both still considered for new systems?

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  • $\begingroup$ I'm not sure it's any more complicated that adding temperature to the flow sensors. $\endgroup$
    – Tiger Guy
    Commented Apr 4, 2022 at 23:12
  • $\begingroup$ There is newer work on this - check out solar water heating. $\endgroup$
    – Solar Mike
    Commented Apr 5, 2022 at 5:18
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    $\begingroup$ My guess is that energy meters that are reliable enough for billing puposes (consisting of flow meter, thermometers and data logger) are more readily available now than 30 years ago. energy meters can (and often do) also log flow and return temperatures, so it's easy to check if the customers fulfil their part of the technical specs $\endgroup$
    – mart
    Commented Apr 5, 2022 at 12:31

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My local reticulated gas supplier measures the amount of gas it supplies customers via flow meters, but it charges on the basis of energy delivered by multiplying the quantity of gas by the heating value of the gas, measured in MJ/m3. After all it is an energy supplier and the customer want energy.

Generally, the heating value of the gas doesn't change so charging for energy delivered this way is convenient and inexpensive. If the heating value of the gas does change, as it has once, it's a simple matter of changing the company's accounting parameters.

Customers of district heating systems as you describe want to be supplied with energy, in this situation heat. The means of supplying the heat is via water. Measuring the volume of water delivered is easy via a flow meter.

One of the issues with delivering energy via hot water is a loss of energy because the water loses heat energy as it flows through the network. The loss will be reduced by insulation of the pipes and possibly other means, but heat will be lost.

By just measuring the amount of water delivered there is no guarantee that the customer has received the amount of heat energy that left the company's facility, or the amount of energy the customer wants. The only way to know the amount of energy that was delivered to the customer's premises is to use an energy meter.

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