Water Meter Calculator

How our water meter calculator works

The British water infrastructure is managed by more than 20 separate water companies, each with its own method for charging for metered and unmetered water tariffs.

The calculator uses the scheme of charges of each supplier to calculate your annual bill, taking into account both consumption and rateable value inputs.

Below is an explanation of how each of these tariffs works:

Unmetered rateable value water calculation

For homes without a meter, water bills are usually calculated using the property’s rateable value rather than actual water use.

Rateable value is used to calculate both water and council tax bills. It represents an assessed value of a home determined by HMRC until 1990, after which these valuations stopped being updated.

The rateable value used for your water bill is therefore based on your property’s 1990 assessment. You can find it on a recent water bill, usually displayed as follows:

Source: Affinity Water – Your bill explained

The home above has a rateable value of £219, which is then utilised to compute water and wastewater usage charges.

Our calculator uses your rateable value and the relevant scheme of charges in your area to estimate your annual water bill without a water meter.

💡Rateable value ignores the thousands. So £219 means the home was valued at £219,000 in 1990 by HMRC.

Measured water calculation

Once a water meter is installed, your water supplier will charge based on the amount of water your home actually uses.

Your water company will conduct regular meter readings to determine your water usage. The usage charge on your bill is then calculated by multiplying your water consumption by the volumetric rates for both water and wastewater.

Here’s an example:

Source: Affinity Water – Your bill explained

Scotland and Northern Ireland water meter requests

Our water meter calculator is designed exclusively for homes in England and Wales. We have excluded Scotland and Northern Ireland from its scope for the following reasons:

• Scotland – Water bills are included in a combined service charge, and you cannot request a free meter from Scottish Water.
• Northern Ireland – You cannot request a free water meter from NI Water.

Why your bill might be higher than the calculator

The calculator estimates water consumption using household size and typical usage patterns, adjusted for whether your household uses more, less, or about the average amount of water.

After your meter is installed, your actual water use may turn out to be higher than expected. These are the three most common reasons why:

• Daily habits – Aspects of your daily routine, such as the time spent in the shower, can have a significant impact on water consumption. For example, showering for 10 minutes instead of 5 can use an additional 27 m³ of water per year, adding roughly £100–£130 to your bill.
• Plumbing issues – Small leaks from a toilet cistern or dripping tap can waste thousands of litres of water each year. With a water meter, all of this usage will count towards your bill.
• Gardening – Water meter calculators typically don’t account for water used by garden hoses or sprinkler systems, which can easily double consumption during the summer months.

Water meter calculator – FAQs

Our water experts answer those frequently asked questions regarding domestic water meters.

How much does a water meter cost?

In England and Wales, requesting the installation of a water meter is usually free of charge.

The exception is where your water company finds it impractical or unreasonably expensive to install a water meter. This can occur when a single incoming water supply pipe serves multiple flats and there is no practical location to install individual meters.

If it is not possible to install a water meter, your water company may suggest switching your supply to an assessed tariff, which instead takes into account the number of occupants in your home.

Who can benefit the most from a water meter?

Owing to how water tariffs are structured, homes of high value with fewer occupants stand to gain significantly from water metering.

Under the rateble value tariff commonly applied to homes without a water meter, your bills are primarily determined by the property’s value. This means you could face high bills despite minimal water usage at your home.

Is it cheaper to have a water meter?

Whether a water meter will save you money depends on several factors:

• The actual volume of water your household consumes.
• The rateable value of your property.
• The specific tariff rules set by your local water company.

Our water meter calculator estimates if your particular household could benefit from reduced water bills by switching to a water meter.

How often is my water meter read?

According to Ofwat, the regulatory body for the water industry, water companies must carry out a meter reading at least once per year.

For billing periods between these readings, your water company will apply an estimated usage figure to your bills.

Increasingly, some water companies are adopting smart water meters, facilitating automatic meter readings.

How do I get back to unmetered charges?

In most parts of the UK, opting for a water meter installation includes a two-year guarantee that your bills will not increase.

Should your initial bill post-installation prove more expensive, you can typically request to revert to a rateable value or assessed water tariff. Some water companies may perform this evaluation automatically.

It is advisable to thoroughly review the terms and conditions associated with your supplier’s “lowest bill guarantee.”

⚠️ In areas experiencing significant water scarcity (parts of Southern Water, South East Water, Thames Water, Affinity Water, and SES Water) the lowest bill guarantee may not be applicable.

How do I request a water meter?

You can request a water meter from your local water company’s website.

Here’s the process once you’ve requested a water meter:

• Water meter survey – An engineer from your water company will visit your property to determine the most suitable location for the water meter. This could be either inside your home or on the pavement outside.
• Water meter installation – An engineer will fit a water meter into your home’s incoming potable water pipe. The meter will start with a zero reading and begin to record your home’s water consumption.
• Your new water tariff – Following the installation of the water meter, your water company will switch your account to a measured water tariff. From your next bill onwards, you will be charged according to your area’s measured tariff rules.