I wanted to see how big this would actually need to be.

Let's say we're using cast iron. Density is 7800 kg/m^3, so you'd need approximately 211 cubic meters of solid cast iron, which is a cube with side length of approximately 6 meters. So you'd need two stories just to fit the thing in your house, and another to be able to lift the required amount.

So that's obviously impractical, let's use a denser metal. The densest metal material is osmium at 22,600 kg/m^3, resulting in a block 73 m^3 which is a cube with side length 4 meters, which still doesn't fit in your basement, but we can probably fit most of the mechanism into two stories.

The densest know element is hassium, which gets you down to a cube with side length 3.4 m, which still doesn't fit in your basement (let alone the height needed to lift) and has the minor drawback of a half-life of 10 seconds.

So short of exotic materials you generally only find in stars, such a system is fairly impractical on the household scale.

I think this example really highlights the main drawback of these kinds of energy storage systems: they take up a lot of volume.