As per FINRA regulations, the margin requirement when holding leveraged Exchange Traded Funds (ETF's) overnight are as follows:

300% (3x) leveraged ETF= 75% on the long side, 90% on the short side.

200% (2x) leveraged ETF= 50% on the long side, 60% on the short side.

If you choose to daytrade ETFs, the stated day-trade buying power for an account will be reduced as follows:

For 2x leveraged ETFS divide your day-trade buying power (DTBP) by 2 (or multiply by 1/2).

For 3x, divide by 3 (or multiply by 1/3).

For example...

Stated Day-Trade Buying Power	leverage of ETF	example	percent of DTBP which can be used	effective DTBP
$100,000	2x	Proshares Ultra Basic Materials (UYM)	50%	$50,000
$100,000	3x	Direxion Daily Energy Bull 3x Shares (ERX)	33.33%	$33,333

To see if a particular ETF is leveraged/has a higher margin rate, see the higher margin requirements stock list.

If you would like to read the complete FINRA rule in accordance with NASD Rule 2520 and Incorporated NYSE Rule 431, see this url:
http://www.finra.org/web/groups/industry/@ip/@reg/@notice/documents/notices/p119906.pdf.