If its got nothing else now. Then, 1 of those electric heaters as back up heat, and a Ductless Heat Pump as main heat and AC. A 18kBtu unit can easily heat/cool a 25x32 shop, way more energy efficient and in the US you can buy and install them yourselves and save a lot of $ vs the ridiculous price installers charge to do a half ass job most of the time...
An air-to-air heat pump has a great deal of merit, Mid-Atlantic "coastal plain", his location. Or my own.
They have come a very long way to "JFDI" wire-and-forget since my first one, early 1970's, a highly problematic "Amana" that I grew short-tempered with and eventually had re-engineered by a friend who was our commercial large-retail building HVAC contractor. After Norm's team "breathed heavily on it" with better components and controls, it ran about 15 years, no further hassle until the female back of the thermostat was no longer tolerable!
Lo these many years on, even Chinese factories are building more of them proper-like to begin with, the next-door neighbour's premium-end Lennox split/plumbed system a real gem and uncanny quiet as well.
The larger of the two sections on my own plate has an 18-foot wide vanilla panelled-roll-up "garage" door. Now and then there is the "recovery" challenge when the entire air charge is swapped-out for ambient outdoors.
Hence my preference for "radiant" heat. That heats the air as a byproduct of first heating the "things" IN the space. Slab, opposing walls, and all the massive "Old Iron" residents come up to temp and act as flywheels.
Forced air units, any heat source, do the reverse. Heat the air first, the "things" in the space warm gradually as a byproduct of the temperature of the air.
Swings and roundabouts over enough time to stabilize, but the radiant is more comfortable, SOONER, wintertimes, for he who has to work in the space, as it resembles sunshine sourced heat.
Conversely, summertimes, "radiant" not even an option, forced air cooling is more comfortable, SOONER anyway as the breeze off even a fan works with our own natural "cooling system" skin, even sweat.
Complicated or costly to gin up a hybrid system for relatively small spaces?
Not really.
This past summer, I experimented with two GE-branded, 5,500 BTU uber small and light 120 VAC window units. Only $120 or so each and mere minutes to install, since remove. At those prices? Why would I
not do the trials?
Lesson Learned? They "peak" well-enough to improve per-room comfort when used at all, but "peak" they or follow-ons shall become. No surprise that their operating efficiency is rather poor.
Keeping my year-round costs down relies on an undersized central system run steadily at its peak efficiency, spot-augmented with less-efficient to run, but cheaper to acquire "boosters" put online only when there is a genuine need, ELSE NOT.
Insulation, and lots of it, plus
control of air in/out, not accidental drafts, is still by far the most important money-saver of all, and the "enabler" of any and all of those other choices at the more affordable costs.
Works for me. No "black magic" to it.
All the info is online, plenty of sources. Mix and match can pay-off.
Add a ration of solar if you can do as well, and not necessarly photo-voltaic.
A bit of sensible heat - residential full or partial water heating, or "taking the chill off" a secondary-use space, for example, can be easier and less long-term hassle than electricity.
After all - cold frames and greenhouses worked even for Grandparent's farm, 1912-1954 with no electricity at all that didn't come off a battery. Natural gas wells, rather!