[dad911]

Clamp on amp meter will tell you current draw.

To convert to watt-hours, you need to know duration (time) it is on. If you want to hack, find an old style analog clock, and wire it into the system. As I recall you had relays turnig on 220v heaters?

Or this should work: https://www.amazon.com/Electric-Meter-100A-Volt-3-Wire/dp/B00GMZRXE8

Maybe this?(not lot of info in description) https://www.amazon.com/dp/B07JB9B2QL/ref=sspa_dk_detail_3?psc=1&pd_rd_i=B07JB9B2QL&pd_rd_w=qUfiM&pf_rd_p=8a8f3917-7900-4ce8-ad90-adf0d53c0985&pd_rd_wg=I8TaP&pf_rd_r=TDPM0ZC1BYZP5Z1TZGGV&pd_rd_r=d2a5a5fa-6a06-11e9-8627-41445435c50e

Here's another: https://www.amazon.com/dp/B00A4VF7U8/ref=psdc_14244481_t1_B00GMZRXE8