The short version: E means estimated, A means actual. An estimated bill is a forecast of your usage, not a record of it. To replace the guess with the truth, read the meter and submit the reading — the next bill corrects itself automatically, up or down. The moment it matters most is switch week: a real closing read is what stops you paying the old supplier for units you use on the new one’s rates.
What does the E beside the reading mean?
Every Irish energy bill shows the meter reading the charges were built on, and beside it a small code that tells you where that number came from. It is the single most useful letter on the bill, and most people have never noticed it.
| Code | What it means | How much to trust the bill |
|---|---|---|
| A — actual | A real reading from your meter: taken by an ESB Networks or Gas Networks Ireland meter reader, or collected remotely from a communicating smart meter. | Fully. The bill charges exactly the units the meter recorded. |
| E — estimated | No reading was available, so the supplier calculated one from your consumption history and a seasonal profile. | As a forecast only. It can run high or low, and the gap grows the longer estimates stack up. |
| C — customer | A reading you submitted yourself. Some suppliers label these separately; others fold them in with actual reads — the key printed on your bill tells you which letters it uses. | As good as an A, assuming you read the right digits. |
One E is nothing to worry about — estimation exists precisely so your bill still arrives when a read does not. The pattern to catch is a run of them: three or four consecutive Es mean every bill for the best part of a year has been fiction, and the eventual correction will be sized to match. Where the reading and its code sit on the page is covered line by line in the electricity bill explainer and the gas bill explainer.
Why is my bill estimated?
An estimate is what a supplier does when the pipeline that normally delivers your reading comes up empty. That happens for a handful of ordinary reasons, none of them your fault and most of them fixable in five minutes.
- The meter reader could not reach the meter. ESB Networks and Gas Networks Ireland read meters on a cycle a few times a year, and if the meter is inside, behind a locked gate, or you were out, that visit produces nothing. Everything between visits is estimated unless you submit a read yourself.
- Your smart meter is not communicating. A smart meter should make estimates rare — but it sends its reads over the mobile network, and homes with poor signal or an unlucky meter location can have a smart meter that records everything and reports nothing. More on this below.
- You just switched or just moved in. A brand-new account has little history at your MPRN or GPRN, so early bills lean on a generic profile until real reads teach the supplier what your household actually does. If no opening read was captured, the very first bill is a guess about a stranger.
- Nobody has submitted a read. The unglamorous, most common reason. Suppliers invite a reading before each bill — app notification, text or email — and if the window passes, the bill is estimated by default.
Notice what is missing from that list: malice. An estimated bill is not a supplier trying to over-charge you — the estimation is mechanical and corrects itself, in either direction, the moment an actual read arrives. The problem is never one estimate; it is what happens when the guesses run unchecked for a year while your life changes underneath them.
How far can an estimate drift from reality?
Estimation algorithms are good at one thing: the shape of a typical year. They know winter bills run heavier than summer ones and they know what your address used historically. What they cannot see is you. Start working from home, plug in an EV, welcome a baby, get the attic insulated, take in a lodger — the estimate keeps billing the household you used to be.
Here is the mechanism, illustrated. The grey bars are what a seasonal estimate might assume; the green bars are what a household that started home-working and charging an EV actually used. Illustrative units only — this is not euro, and not any real bill.
Two things make this worse than it looks. First, the gap accumulates — in the illustration above, 74 units of real usage went unbilled across the year, and every one of them is still owed. Second, the drift is invisible on the bill: an estimated bill looks exactly like a normal bill, with a normal-looking total, right up until an actual read arrives and the whole year trues up at once. The direction can just as easily run the other way — a household that downsized, insulated or emptied out gets over-billed quarter after quarter and never knows it is building a credit.
How do I fix an estimated bill?
This is one of the highest-yield five-minute jobs in household admin. You are not arguing with anyone or filling in a dispute form — you are simply supplying the number the system was missing.
- Read the meter. All the digits, left to right, ignoring any red or decimal digits your supplier says to skip. NightSaver meters have two registers, smart meters need a button-press or two — the electricity meter guide and gas meter guide walk every meter type.
- Photograph it. Ten seconds, and it settles any later disagreement about what the meter said and when. Make sure the digits and, ideally, the meter serial are legible.
- Submit the read. Through your supplier’s app or phone line, or through the network operators directly — the routes and what each needs are in how to submit a meter reading.
- Check the next bill. The reading code should now show A or C, and the bill will carry the correction — a credit if the estimates ran high, a catch-up charge if they ran low.
- Make it a habit. One read per billing cycle, prompted by the supplier’s reminder, keeps every future bill anchored to reality. If that is too much, prioritise switch day, moving day, and the run-in to winter.
A detail worth knowing: because the meter is cumulative, you never need to reconstruct the missing months. One actual read tells the supplier the total truth since the last real read, and the arithmetic sorts itself out. There is no penalty for a big correction and no time limit on submitting — later is always better than never.
What reads should I take when I switch supplier?
The switch-week read is the one that pays you. When you change supplier, one reading becomes both the old supplier’s closing read and the new supplier’s opening read. If that number is an over-estimate, units you have not used yet are billed by the old supplier — usually at the standard rate you were escaping — while your shiny new discount starts late. You have, in effect, gifted the old supplier a slice of your first new-deal bills.
So on the day you sign up: read every meter you are switching, photograph each one, and submit the figures to the new supplier. Then check the old supplier’s final bill closes on the same number the new one opens on. Same ritual on moving day — an opening read in a new home is what stops you paying for the previous occupant’s units.
An estimated closing read is not a catastrophe — the credit eventually washes back through the final bill if the numbers are later corrected — but it is friction, phone calls and waiting that a photograph and two minutes of typing make unnecessary. The full changeover sequence, including when the final bill should arrive, is in what happens when you switch.
Do smart meters end estimated bills?
Mostly, and that is genuinely one of their best features. A communicating smart meter sends reads to ESB Networks automatically, so bills arrive marked A without anyone crawling into the meter cabinet. If yours is working, estimated bills should become a rarity reserved for network hiccups.
The honest caveat is the word communicating. Smart meters report over the mobile network, and a minority of homes — granite walls, rural blackspots, meters boxed into unfortunate corners — have a meter with a weak or absent connection. The meter still records flawlessly; it just cannot phone the reads home, and the supplier quietly falls back on estimates. If your bills still show E months after a smart meter install, that is the likely story: read the display yourself, submit it like any other read, and raise the comms issue with ESB Networks. How the meter types, communication levels and remote reads fit together is covered in the smart meters guide.
Gas is its own case: the smart rollout is an electricity programme, so gas meters remain read-by-human (or read-by-you) for now, and gas bills stay the more estimate-prone of the two fuels. A gas read once a cycle earns its keep.
What are the two ways estimates cost you money?
Neither trap involves the supplier doing anything wrong — both are just the arithmetic of guessing left uncorrected. Knowing which side of the drift you are on tells you how urgent the fix is.
| The drift | What it feels like | What actually happened | The fix |
|---|---|---|---|
| Over-estimated for months | Bills feel high, but plausible. Then an actual read produces a surprisingly large credit. | You lent the supplier your money, interest-free, for months. Fine as a forced savings scheme; bad as a use of your cash. | Submit a read, take the credit — and ask for it as a refund rather than leaving it parked on the account. |
| Under-estimated for months | Bills feel pleasantly low. Then one bill arrives carrying every unit the estimates missed. | A catch-up, not a penalty — you used the energy, you are paying late. But it lands as one lump at the worst possible moment. | Submit reads before the gap grows; if the catch-up is already big, agree a payment plan rather than letting it age. |
The under-estimate trap has one extra tooth worth naming calmly. If a catch-up bill goes unpaid long enough, it becomes ordinary arrears — and arrears of €225 or more, over 60 days overdue, allow a supplier to flag a future switch, delaying your move to a cheaper deal until the balance is handled. That is a reason to engage early, not to panic: suppliers must offer payment plans, spreading a catch-up is routine, and the whole flag mechanism — plus what to do if you are already behind — is explained in switching in arrears.
And the over-estimate trap has a mirror-image consolation: your money is never lost, only parked. Every over-billed unit comes back once a real read lands, and any credit left when you leave a supplier must be refunded after the final bill. The only thing you cannot get back is the use of the money in the meantime — which is the entire argument for the five-minute read.
Where to next?
- How to submit a meter reading — the app, phone and network-operator routes, per fuel.
- How to read an electricity meter and how to read a gas meter — which digits, which registers, which buttons.
- Electricity bill explained and gas bill explained — every other line on the page, decoded.
- How to switch energy supplier — if accurate bills have revealed you are paying too much. matched.ie is not a CRU-accredited comparison site; the accredited comparators are listed on cru.ie, and our own year-1-and-year-2 ranking is at best energy in Ireland.
