How many kVA?

[Garald]

Yet another instalment of the saga: renovation of a triplex (half of the ground-floor, all of the first floor and all of the attic of a house from 1930) in the Paris area.

 

The previous owners had gas heating and also cooked with gas. They had a 6kVA electricity subscription.

 

That will obviously not be enough now. While I'll go for either a 7kW or 8kW heat pump (meaning it will consume less than 3kW even at low temperatures, where its COP is far from best), the peak power that a standard induction stovetop can consume goes up to 7.4kW, and then of course there's the washer and the dryer (not to speak of lights and computers).

 

Should I go for 9kVA or 12kVA? (I take 15kVA would be an extreme overcalculation?) One has to pay about 35 euros per year for each 3kVA by which one raises the limit; if there are other costs associated with a higher limite, I'm not aware of them. We are on monophasic.

 

[ProDave]

We are not used to this in the UK, even the smallest supply with a 40A fuse is about 9.6kVA

 

So to get a higher rating, you pay more per year?  What we know here as the standing charge.  Does the unit charge (charge per kWh used) also go up?

 

Going for the maximum would be another 105 Euros per year.  That does not sound too bad?

 

[Garald]

Once you are at 6kVA, the unit charge does not change (as of now). Yes, when you go up 3kVA in the rating, you pay 35 eur per year. So, yes, going for 15kVA would not be exactly a financial tragedy, but I'm not sure of how I would use that much electricity. More to the point, as I've just found out, there may be a hard limit of 12kV on monophase (36kV on triphase): https://www.kelwatt.fr/guide/compteur/douze-kva 

 

I also learn from there that 70% of all residential properties in France have a 6kVA subscription. (3kVA is for bedsits.) Apparently, 12kVA is rare (op. cit.).

 

I guess 12kVA makes sense? 

 

(Even then, I take this means I should not do my laundry while cooking for a large group of people in winter. I had never thought of it.)

 

Edited December 26, 2022 by Garald

[SteamyTea]

General question.

How the the kVA limit enforced?

Is it though hardware i.e. the main fuse blows, or though software i.e. the meter logs and reports over current?

 

I remember having similar problem when we lived in France over 50 years ago.

Edited December 27, 2022 by SteamyTea

[ProDave]

I believe the limit is enforced with a supplier owned circuit breaker (not fuse) and if it trips the supplier has to come and reset it.  

 

Well this is one way to limit energy usage, it makes realise how good the UK system is with often a 100A fuse being the only thing to stop excess uses.

 

The domestic appliances are easy to control, i.e. don;t put your washing machine or tumble dryer on while you are cooking your dinner etc.  But you have to assume the ASHP can turn on at any time it wants to, so if you are installing say a 12kW ASHP which might consume up to 5kW of electricity, then increase your supply rating by 6kW so it can be on at any time without having to interfere with any of your normal usage.