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Is there a device that can evenly split the load on two separate panels?

For example,

Panel A ——————-\
                >-[ device ]— Load
Panel B ——————-/

The use case is, up stairs and down stairs tenants have separate electric service. There is a shared washer and dryer in the basement. Both machines are using the down stairs electricity. Is there a device that can be plugged into both panels and draw the power evenly to share the cost?

isherwood
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YarGnawh
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    You can meter the power or install a transfer switch but this would be an honor system to transfer from 1 supply to the other, metering would be cheaper than a transfer setup. – Ed Beal Sep 09 '20 at 02:02
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    Can you post photos of the existing electric metering hardware please? We can help you get out of the jam you're in, but only if we know more about your precise configuration... – ThreePhaseEel Sep 09 '20 at 02:39

3 Answers3

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I don't see any practical way, and by that I mean cost effective and in a manner that both sides would be satisfied with the result. See Ed Beal's comment.

You could set up a transfer switch (a double pole double throw switch with a neutral position). The common poles would connect to the appliance and each side of the switch would connect to opposing panels including breaking the neutral. Then whom ever would want to use the appliance would have to be able to switch to his panel. When they were finished the circuit would have to be reset to the neutral position automatically. To keep one person from using the other persons power you would have to set up some sort of interlock where one side could only turn on their power and not the other. It is also important to note that no one really manufacturers this sort of device so control would be a one off set of parts.

In most multi-residential buildings you have shared appliances on a House Panel which serves a common area and the utility charge is divided up and billed as part of the rent.

Hope this helps.

Retired Master Electrician
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You are assuming that the tenants use the machines about equally, and you want to split the cost of the electricity. You could leave the machines powered by the downstairs panel and use a separate metering device, such as a Kill-a-Watt monitor, to directly measure power usage of the machines.

The installation should be tamper-proof to the prevent the upstairs tenant from bypassing it or the downstairs tenant from plugging other stuff into it. It doesn't need to be absolutely secure, just enough to keep honest tenants honest.

Periodically the upstairs tenant pays the downstairs tenant half of the cost calculated by the Kill-o-Watt, which is then reset.

A. I. Breveleri
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Run cables from switched boxes in each apartment to power points (outlets) in the basement. Then each tenant uses their own power point there, after turning it on in their apartment first. After finishing they switch off their own box to prevent the other tenant "stealing" their electricity. Common solution locally.

Polypipe Wrangler
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  • While common where you're at, this is not legal in the US -- NEC 210.25(A) forbids it as now you have a dwelling unit branch circuit supplying a load that's not solely associated with that dwelling unit – ThreePhaseEel Sep 09 '20 at 23:50