Lately I have been hacking on the home automation project which should at some point tie together my current ad-hoc house and greenhouse control systems. One part of that system will be energy usage optimization with wireless smartplugs, which uses Plugwise smartplugs and the python-plugwise library that I wrote. The main (and more or less the only :-)) appliance that I can make energy savings on using automation is the electric boiler. It’s an old 40-50l heater that hasn’t been cleaned for at least 3 years so it probably contains a lot of limescale and sludge which causes it to use far more power that it should. Hopefully I will get around to cleaning it soon.

I haven’t implemented any fancy logic for controlling it yet and instead I just use a simple crontab that switches the boiler on for 3 hours total each day – somewhere around when we leave for work and again before we get back home.

So far it seems to be enough to provide hot water for 2 persons on working days and it wastes around 2 times less power than it would if it was permanently switched on:

So assuming this difference holds true for larger periods of time I will get energy savings of ~4kWh per day. If I only use this control method on working days it will give me somewhere around 80kWh savings per month. Currently I pay 0.1026 € per kWh so I should save somewhere around 8 € per month, and 96 € per year on this appliance. So these smartplugs should pay for themselves in about 1.5 years. Currently Estonia has the cheapest price of electricity in Europe which can only go up as the energy market opens up and hidden subsidities are removed so the savings will probably be even more substantial in the not so distant future.