It is always best to slightly oversize when selecting baseboard heaters. There is no loss of efficiency by heating your space with baseboard heaters that are slightly larger than the minimum requirements.
For example, a 30-amp circuit can accommodate a baseboard heater rated for 500 square feet or 4,500 watts, but the same heater will be more efficient at heating a smaller room (assuming the circuit size is appropriate). It's also possible to put two or more baseboard heaters on the same electrical circuit as long as their total combined wattage is not higher than the circuit's maximum capacity.
Total Area of Room (sq. ft.) Recommended Heater Rating (watts) Electrical Circuit Size Needed (240 volts)
you need a 20% extra capacity. you need to add up other appliances, microwave 1000w, stove 3000w, dryer 2000w... lights (old bulbs) will adds up another 1000w.
At 240V, a 3,000 W baseboard heater draws 12.5 amps.(网上查来的）
Now, a 20-amp circuit can only handle devices that draw up to 20 amps. We can see that, if we have a 240V circuit, we can run a 3,000 W heater on a 20-amp circuit. That’s because it draws less than 20 amps; 12.5 amps, to be exact.
我知道200安培的service是没有问题的，但是最近一个出租房的heat pump系统有问题，至少indoor unit需要换掉outdoor unit情况还不清楚，ductwork还需要清理,费用往少的说，也差不多2000，而且这方面的人不能随时叫到，最好的选择就是改electric baseboard heating,我自己以前做过一些，知道怎么装,但就是不知道目前100安培的service是否能支持如下的设计 楼下1500 w 的baseboard heater 3个，1000w 的一个，楼上也是同样数目的瓦数和个数的baseboard heaters。网上查的结论好像是装是可以装但用起来如果超过rated service可能会跳闸，我约了人来做，但是靠不住，几次爽约，而租客是SECTION 8不解决这个问题会有麻烦，好在我与租客关系不错，平常他受了我的好处，暂时不至于闹事但是我必须解决这个问题，否则是个潜在的麻烦。
burn down the house...
另外我估计实际上我用8000瓦就差不多够了，所以可以降低所买baseboard heater的瓦数
不过我实际上可以降低购买baseboard heater 所需的瓦数。
Manufacturer's Recommended Heating NeedsIt is always best to slightly oversize when selecting baseboard heaters. There is no loss of efficiency by heating your space with baseboard heaters that are slightly larger than the minimum requirements.
For example, a 30-amp circuit can accommodate a baseboard heater rated for 500 square feet or 4,500 watts, but the same heater will be more efficient at heating a smaller room (assuming the circuit size is appropriate). It's also possible to put two or more baseboard heaters on the same electrical circuit as long as their total combined wattage is not higher than the circuit's maximum capacity.
有些地方其实不用热气，如储藏室
you need a 20% extra capacity. you need to add up other appliances, microwave 1000w, stove 3000w, dryer 2000w... lights (old bulbs) will adds up another 1000w.
如果所有的主要电器都在同时启动的电流，就是你需要的最大的电流表。
你可以自己负责，如果是我，不敢。100安培的屋子用电暖，总功率达1万瓦以上，还不算电烤箱，电吹风机，微波炉，那都是上千的功率。对，电路有安全保护跳闸，但跳闸后，你怎么办？暖气不开了？电器不用了？，让房客不要同时使用各电器？
技术上，你要把每个房间用电暖的这一路线升级到220伏和相应的电流规格，还是那句话，您自己做，你自己负责，如果是我，收的钱可是要木老老的。
为了应急，我可以改动一下设计，暂时对付目前状况，同时再申请升级service 到200安培，这个需要时间但是为今后打算。
Now, a 20-amp circuit can only handle devices that draw up to 20 amps. We can see that, if we have a 240V circuit, we can run a 3,000 W heater on a 20-amp circuit. That’s because it draws less than 20 amps; 12.5 amps, to be exact.
我的结论是大致能够应付我的情况
家里随便开几个space heater的电费就能吓死人。改装的这点费用相对于电费来说根本算不上什么。当然如果是德州佛州的就无所谓了。
Most space heaters use on average 1,500 Watts of electricity and cost about 15¢ an hour to operate.
我好像听电工说起过，不知道对不对。
1. 走火的可能性太大了， 要报告保险公司你取暖方式改变
2. 计算是要考虑所有电器一起启动， 然后加裕量
租客应该会配合，因为是他出电钱，只要告诉他这样省电，他就会满意。