Private water is often called free because there is no usual water utility bill for each cubic metre. However, the system uses electricity and needs testing, maintenance and sometimes repairs. Calculating annual unit cost helps compare solutions. There is no single rate suitable for all Lithuania: the result depends on the particular system, actual use and selected accounting period.
First decide what you are comparing
You can calculate annual operating expenditure alone or the full cost including the initial investment. Both tables are useful, but must not be mixed. Adding installation to one option while counting only electricity for the other creates an unfair comparison. State clearly above the table which scope is included and the period covered by the data.
Also distinguish water abstraction from wastewater management. Source electricity and filters do not automatically cover all costs associated with the water used. When comparing with public supply, check the bill's components: water supply and wastewater may be separate services. Totals covering different scopes cannot be treated as a comparison of source costs alone.
Annual volume must be genuine
The most convenient basis is the opening and closing readings of a reliable meter. Note substantial irrigation, construction use or tank filling separately. Without a meter, the calculated volume must be called an estimate. Resident numbers and a general online average alone do not establish a particular household's water consumption.
The denominator in the unit cost calculation is crucial. The same annual maintenance sum divided by a small seasonal volume produces a higher cost per cubic metre than in a permanently occupied home. This does not mean the seasonal system is technically poor. Fixed costs are simply spread over less consumption. Always show the annual total alongside the unit cost.
Electricity consumption is best measured
If suitable separate metering is installed, use actual kilowatt-hours and the price applied on your bill. State whether taxes are included and which period's tariff was used. The motor's rated power alone does not establish all annual consumption, because operating time and actual system conditions matter. Metering equipment must be installed by a suitably qualified person.
For an indicative calculation, electrical power can be multiplied by operating time, with assumptions clearly stated. For example, one kilowatt-hour is the energy used by one kilowatt of power operating for one hour. However, the power shown on a pump is not always its exact instantaneous electrical consumption. This calculation must therefore not be presented as an actual meter reading.
The system duty point changes costs
Pump consumption depends on the selected duty and pipework conditions. The Grundfos engineering manual explains the relationship between the pump and the complete water system. For the owner, this means that comparing two motors' power ratings alone is insufficient. Suitability must be assessed against the required flow, pressure and the source's capacity.
Frequent cycling or inappropriate control may indicate a technical problem, but do not diagnose it solely from a higher electricity bill. Record changes and contact a specialist. Do not alter protection devices or settings yourself merely to reduce a number in the table. The system must first operate safely and as intended.
Water testing is not an incidental expense
Include laboratory tests actually carried out and, where necessary, professional sampling. The test programme depends on the source, risk and changes in circumstances. NMVRVI information distinguishes well and borehole parameters and sample requirements. This helps explain why two test orders may have different prices because their scope differs.
Do not create savings simply by omitting tests from the accounts. The total will look lower, but will no longer describe a safely maintained system. If testing followed an exceptional event, record it separately from the normal annual plan. This shows which costs recur and which relate to a particular repair or flood.
Filter maintenance and backwash water
If filters are used, include cartridges, media, treatment chemicals, specialist labour and their electricity use where significant. Also assess water consumed during servicing and its drainage. The volume of filtered water used and the total abstracted from the source may differ. Record this difference, particularly when comparing equipment options.
Select filters according to test results, not the desire for a lower cost in a spreadsheet alone. If system capacity is insufficient or backwashing is unsuitable, cheaper operation may simply mean the required outcome is not achieved. Read about water treatment principles in the article on filter selection. Different filtration technologies do not all solve the same problem.
Repairs and initial installation
A major repair in one year may substantially change the result, so a history covering several years is useful too. Distinguish expenditure actually paid from a planned reserve. A reserve is not an actual failure, but helps avoid assuming the equipment will operate without any future costs. Show its assumptions openly.
You may allocate the initial investment over a chosen comparison period, but this is an economic estimate, not one year's actual bill. State the period and do not present it as guaranteed equipment life. When comparing sources, use the same method for both options. This reveals which assumptions most affect the result.
The owner's time
If comparing broader economic benefits, record your own maintenance time separately. It need not be converted into money, but regular filter servicing and record keeping are not entirely effortless. Show this line separately from services actually paid for so the calculation stays transparent and verifiable.
How should you present the final figure?
Divide the included annual expenditure by a clearly defined volume of useful water. You will probably have several scenarios rather than one absolute truth: operating expenditure, cost including investment and a less favourable year's scenario. Keep starting values, dates and sources visible in each. The calculation can then be updated rather than recreated.
In your enquiry, provide the annual volume, equipment list and available cost items. If data is not yet available, start with metering and a maintenance log. Private water can be a sensible solution, but an honest cost calculation must show the entire chosen scope, not just the cost that is easiest to measure.
Information sources
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