Convert kWh to watts per m²

Question

I am from a computer science background, I need some help with some electrical engineering problem.

Electricity consumption for a home in the last 56 days is 7561 kWh.

There are two floors. The combined area is 300 square meters.

Can I use this information to get watts per m² for this house?

Assuming that this is a solar energy calculation and that you mean Watts per meter squared (small m for meters), this is not enough information. Tell us the area of the solar cells and we can calculate the Watts per meter squared required. Or, tell us the Watts per meter squared of the solar cell and we can calculate the area required. — Mattman944, Mar 20 '20 at 14:03
To convert it to IT speak, "Download data for this month was 2.3 TB. How much is this in kB / m²?" — Transistor, Mar 20 '20 at 14:25
Were you taught dimensional analysis in school? Either way, here is a reminder: https://en.m.wikipedia.org/wiki/Dimensional_analysis — winny, Mar 20 '20 at 15:40
Watts consumed per m² of floor space does not appear to be a particularly useful measure. Seems like an XY problem to me. What are you really trying to work out here? — brhans, Mar 20 '20 at 16:14
@brhans I oppose. For energy efficiency calculations a breakdown on living area is standard. Usually it's given in kWh/(m²*a). This can, of course, be converted into W/m². However that's usually calculated for all energy sources not only electricity. — Ariser, Mar 23 '20 at 10:54

Justme · Answer 1 · 2020-03-20T14:21:04.453

4

No, the units are not compatible in any way. Unless you have an area.

edited Mar 20 '20 at 14:21

answered Mar 20 '20 at 14:02

Justme

Neil_UK · Answer 2 · 2020-03-20T15:37:15.387

2

7561 kWh per 56 days is about 135 kWh per day, or 5.6 kWh per hour, more simply written as 5.6 kW.

If the relevant area you had in mind is 1m², then that's 5.6 kW/m².

If you were thinking of 1km², then it's 5.6 mW/m².

Did you have an area in mind?

(edit) Now that the OP has let on that the area is 300 m², we can divide that 5600 W by 300 to get about 18.7 W/m² (/edit)

edited Mar 20 '20 at 15:37

answered Mar 20 '20 at 14:04

Neil_UK

There are two floors. Combined area is 300 Square Meter. – user1847624 Mar 20 '20 at 14:45
1

@user1847624 edit that information into your original question – Neil_UK Mar 20 '20 at 15:35
5.6 kw is a lot for a house. Does it have resistive electric heat? The power company figures most houses average about 1kw. – Harper - Reinstate Monica Mar 21 '20 at 03:05

score 2 · Answer 3 · answered Mar 20 '20 at 15:58

Now that you've posted all the required information, an answer is possible.

56 days is 1344 hours (56 days X 24 hours per day.)

You have 7561 kilowatt hours of energy consumed.

Divide the energy by the time to get average power.

That's 7561 kWh/ 1344 hours gives an average of 5.62 kW.

Divide 5.62 kW by 300 square meters and you come up with 18 watts per square meter.

That's an average of the power consumed by every square meter of your house over 56 days.

I don't know how much good it really does to know that number.

Is it for some kind of home energy efficiency rating or something?

score 0 · Answer 4 · answered Mar 20 '20 at 15:08

The beauty of SI is how you can easily balance units and convert between domains.

So 7561 kWh ...

kWh == J/s * s == kg⋅m2⋅s−2

While you cannot express it in Watts per m² (without doing other funky units around it), you can express it in kg m² per s²

but then you could say that kg⋅m2⋅s−2 is equivalent to N.m == Pa⋅m3 so a kWh could be express as Newton-metres are Pascal per unit volume

4 Answers4