I’ve yet to see a MHEV that’s worth it. The somewhat marginal fuel savings won’t offset the increase in price in years and years, it’s just pointless.
In regards to whether or not a PHEV is worth it, it depends on you entirely. You say “low mileage user”, it doesn’t actually matter whether or not you do a lot of miles or very little – it’s the length of the average journey that matters (you can have low mileage, but have the average journey be 150 miles long).
If your average journey length is close to the electric range of a PHEV, it’s absolutely worth considering. If it’s slightly more (as in, twice the electric range), it’s still worth it. If it’s considerably more (100+ miles), it starts to taper off.
As an example, we did an extended test drive with the car we eventually ordered (Golf GTE), with an advertised electric range of around 37ish miles. The test drive was around 80 miles, and we managed around 115mpg average (we saw higher numbers, but being a GTE – and not ours on top – we did hoon a little here and there). That’s absolutely worth the increase in AP to us – especially considering that our average journey is well within the electric only range. Now, it’s not a “big” car (i assume you’re talking the Tucson etc), but it translates to those too, just with a lower mpg/range.
This is of course assuming that you’re able to charge (either via granny cable or wallbox) the PHEV.
We expect to save around £800 in petrol (.. depending on energy prices, sigh) annually, and we also somewhat intend to keep it for 5 years. You’d need to do the math yourself, and more importantly, just test drive what you’d like to know about. Dealerships usually are accommodating longer test drives (they might ask you to put a little bit of petrol back in – just immediately offer to refuel what you use to maybe sway the salesman), just walk into the dealership and test drive the large PHEV for around 100 miles mixed (A roads, motorway, city) and see where it lands. Do the math from there.