The costs of intermittent renewable energy systems (IRES) and power storage technologies are compared on a level playing field to those of natural gas combined cycle power plants with CO2 capture and storage (NGCC–CCS). To account for technological progress over time, an “experience curve” approach is used to project future levelised costs of electricity (LCOE) based on technology progress ratios and deployment rates in worldwide energy scenarios, together with European energy and technology cost estimates. Under base case assumptions, the LCOE in 2040 for baseload NGCC–CCS plants is estimated to be 71€2012/MWh. In contrast, the LCOE for electricity generated intermittently from IRES is estimated at 68, 82, and 104€2012/MWh for concentrated solar power, offshore wind, and photovoltaic systems, respectively. Considering uncertainties in costs, deployment rates and geographical conditions, LCOE ranges for IRES are wider than for NGCC–CCS. We also assess energy storage technologies versus NGCC–CCS as backup options for IRES. Here, for base case assumptions NGCC–CCS with an LCOE of 90€2012/MWh in 2040 is more costly than pumped hydro storage (PHS) or compressed air and energy storage (CAES) with LCOEs of 57 and 88€2012/MWh, respectively. Projected costs for battery backup are 78, 149, and 321€2012/MWh for Zn–Br, ZEBRA, and Li-ion battery systems, respectively. Finally, we compare four stylised low-carbon systems on a common basis (including all ancillary costs for IRES). In the 2040 base case, the system employing only NGCC–CCS has the lowest LCOE and lowest cost of CO2 avoided with CO2 emissions of 45kg/MWh. A zero CO2 emission system with IRES plus PHS as backup is 42% more expensive in terms of LCOE, and 13% more costly than a system with IRES plus NGCC–CCS backup with emissions of 23kg CO2/MWh. Sensitivity results and study limitations are fully discussed within the paper.