Dark energy has a finite density, approximately 68% of the total energy density of the Universe. Assuming for simplicity a nonvarying Hubble constant H, our cosmological event horizon is at a distance c/H away (c = speed of light). Since c/H is finite, the total dark energy within our observable universe is finite. If the actual Universe is infinite, extending forever beyond our cosmological event horizon, then the total dark energy is infinite, but that beyond our cosmological event horizon can never interact with us. But the above neglects the negative gravitational potential energy of the dark energy in the gravitational field of the Universe. Counting this negative gravitational potential energy, the total energy of the Universe is zero.

Hi the energy of dark energy  in the observable Univrese is 68%. For the Universe to appear flat to within 1% or so, one can deduce that our total Universe is at leat 100  times bigger, the total dark energy in the UNiverse should be at least 100 times as large as the observable Universe and hence contain at least 100 times more energy than this.

The most logical view of the multiverse is that each Universe is finite, but much much larger than the observable Universe. Beyond that there is infinity, but an infinity of material nothingness.

'Infinite' is a Geometrical Abstract and it is not possible  that anything can be of Infinite Measure in any Defined Units .It is not a real quantity. Dark Energy though according to Equipoise Divine Metaphysics based on Principle Pattern, and the Darkon Expansive Force Secondary Principle Pattern can exist outside Spacetime boundaries as a field and is difficult to quantify.

Dark energy is the energy of the expanding gravitational field.  It has been calculated from the R-W metric and equals 2/3 of the total energy.  The other 1/3 is matter.

We first agree on a model, and then fit model parameters with data. Concordance model emerged in late 90s which accounted for observed data including those of luminosity-redshift plot of high red shift supernovae. Such data could be explained in CDM model if it is extended by including Einstein's cosmological constant; this new model which is  called ΛCDM model can explain observed data.

Because  Λ is a universal constant, dark-energy density per unit volume is a constant. As space expands, more volume comes into existence which means more dark energy. As dark energy is repulsive, more space is created, and hence more dark energy which is an inherent property of space. This is exponential expansion. For finite age of the universe, universe is also finite not infinite. Neither linear nor exponential expansion can lead to infinite volume at a finite time.

But there exists alternative models which can also explain luminosity-redshift relations. These are 1) Modified Newtonian Dynamics 2) Modified gravity 3) Large scale variation of matter density of the universe.

 If the universe is described by either k=0 (flat model) or k=-1 (open model) then at any given epoch, the spatial volume of the universe is infinite. And since matter density on   large scales (> 500 Mpc) is uniform, the total mass (or, equivalently,  energy) of the universe (with k not equal to +1) is infinite whether there is dark energy (with positive energy density)  or not.