Jodie wrote:

"Mike" wrote in message
...

"Rod" wrote in message
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The meter in your cupboard? Do you really need it so precise?

and if this is so important. Get a cheaper hobby, you cannot afford to
keep
cactus

----
Ah, most helpful

There are devices out there that will measure what you want. They are
sometimes called watt-hour meters. Most are expensive, but I know a
cactophile with a taste for gadgets who has one (RS do one for ~£160).
This is about what I expect to spend heating my greenhouse for a year so
not surpringly I don't own one...

I am sure I have seen a cheaper one rated to about 3kW but can't recall
where at the moment. A quick and dirty rule of thumb is that the cost to
maintain the temperature an extra 5C above ambient roughly doubles.

If you ask around cacti and orchid growers you will doubtless find an
answer. The latter have even more expensive tastes in plants and climate
control so tend to have more sophisticated automation.

Regards,
Martin Brown