Heat (Btu) meters have been used widely as low-cost instruments for evaluating performance active solar energy systems. In Europe these devices have been used for many years as revenue meters in district heating/cooling systems. The recent trend to third-party financing for capital-intensive solar energy systems has created a growing need for billing meters in this country also. Since !979, the authors has been using energy meters as the primary instrumentation for long-term evaluation of active solar energy systems. To support this effort, a Btu meter test stand was developed that provides calibration of energy and flow. This paper reviews Btu meter technology and describes experiences with Btu meters in evaluating active solar energy systems. It also provides recent calibration results of some commercially available meters.

Units: Dual