The company placed just over 19.4m shares at 900p each.
In a statement announcing the placing late on Monday, non-executive chairman Miriam Greenwood said: "Our contracted smart meter order pipeline and pipeline of grid-scale battery projects represent significant growth opportunities for SMS, as the group continues to enable the UK's transition to a low carbon energy economy. This next stage of SMS' growth is expected to deliver attractive returns to our shareholders.
"Our recently increased £420m debt facility demonstrates the significant support for our business model, and together with internally generated cash and this proposed fundraising, will enable SMS to invest in the substantial identified growth opportunities ahead and drive long term shareholder value."
At 1050 BST, the shares were down 15% at 868.00p.