I have a house of about 120 square meters with 3 bedrooms and I want to know what amperage capacity I should get from the electricity company. Right now I have several appliances: refrigerator, washing machine, window air conditioner, and electric water heater. How many amps should be enough for me?
With 32 amps you're safe for that house, but before you sign up, check what the actual simultaneous demand is: the fridge and water heater almost never draw power at the same time the AC is running full blast. A trick that works is calling the utility company and asking them to check what amperage your current meter has and how consumption has looked historically in similar cases in your neighborhood, because they see patterns that don't show up in generic tables. If you start with 25 and later need more, changing the contract is a hassle but doable, so better not go too low.
For a 120 square-meter house with that type of appliances, you'd typically do well with somewhere between 25 and 32 amps. Most single-family homes that size with those kinds of appliances sign up in that range. If you've got a window air conditioner and an electric water heater, those are the ones that "demand" the most, so you can't go too tight. A refrigerator and a washing machine are relatively moderate in consumption, but when several things start running at the same time is when things ramp up.
The ideal thing would be to do a calculation adding up the power of your most important appliances. The electric water heater is probably the heaviest load you've got, followed by the air conditioner. If your heater uses 2000-3000W and the AC is around 1000-1500W, those two alone are already at 3500-4500W. Adding the washing machine, refrigerator, and whatever you use in the kitchen, you easily hit 5000-6000W at peak consumption. With a voltage of 230V (which is standard in Spain), that calls for around 25-30 amps without any stress.
My advice is to call your electrical distributor and tell them what you've got installed - they usually give you a pretty accurate recommendation. If down the road you want to install more things or switch to electric heating, you can always bump it up. Better to have some headroom than to come up short and have your breakers tripping every other day.
Depending on how you use those appliances, 25 amps should be more than enough for you. What matters is whether you turn them all on at the same time or not.
The thing is, a lot of people get obsessed with getting a ton of amps "just in case" and then end up overpaying. If you use the air conditioning, washing machine, and water heater at different times of day (which is normal), 25 amps works perfectly. The problem comes up when someone tries to run everything at once: AC at full blast, dryer, oven, and electric water heater all at the same time. That's when it trips.
My recommendation is to call your utility company and explain what appliances you have. They know exactly how much each thing uses and can give you a more accurate answer than any of us. If you start with 25 and then see your power cutting out constantly, you can always bump it up to 32, but odds are you won't need to.
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