The new house has a prepay electricity meter. My initial reaction was that I'd have to get NIE to come out and replace it with a normal meter, as I have a perception that card meters are awkward and expensive. However some investigation revealed that a keypad meter gets the same 2.5% discount that paying quarterly by direct debit does. The only way to get a larger discount (4%) is to pay a fixed amount monthly by DD.

That would still leave the annoyance of having to remember to top up, but it can be done over the phone with an automated system (you get a 20 digit number to key into the meter) and won't turn off supply overnight or at weekends apparently. Plus, and this is the real reason I'm giving it a while before switching away, it has a nice little satellite keypad/LCD unit. Connected to the main meter unit via a 4 core low voltage style cable. Bets on those being power, ground, rx and tx? You can query the meter on various things, some of which are crying out to be hooked up to a Munin plugin.

The meter is made by PRI and seems to be a Liberty 1E. PRI have a vague page about comms, but little useful information about how to do anything or if the end user can buy anything suitable. I'll drop them an email, but it might just be a case of trying to reverse engineer the keypad protocol so I can talk it. The processor in the satellite is just a Mitsubishi M38223M which has some serial pins, so hopefully it'll be RS232 at TTL levels and something fairly basic over that.

However, before I go about doing this, has anyone else any experience of these meters and care to share details?