This article was originally published in the May/June 1993 issue of Home Energy Magazine. Some formatting inconsistencies may be evident in older archive content.



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Home Energy Magazine Online May/June 1993




Trends in Energy is a bulletin of residential energy conservation issues. It covers items ranging from the latest policy issues to the newest energy technologies. If you have items that would be of interest, please send them to: Trends Department, Home Energy, 2124 Kittredge St., No. 95, Berkeley, CA 94704.


SMUD'S Solar Water Heating Program

The Sacramento Municipal Utility District (SMUD) serves roughly 60,000 residential customers with electric water heaters, each consuming up to 5,500 kWh annually. The installation of solar water heater systems in these homes is yielding results that dwarf those of almost any other residential conservation measure and is providing significant summer peak load relief for SMUD.

In 1992, SMUD completed a seven-month contractor-driven rebate and financing program, exceeding by 100 the goal of 800 system sales. All installations were inspected by SMUD using the Solar Rating and Certification Corporation (SRCC) OG-300 guidelines as the standard. We found that the average household size of customers installing systems was 3.9 persons. (The average household in Sacramento has 2.8 persons.) Since hot water loads increase with household size, we expect annual energy savings from each installation to exceed 3,000 kWh, saving roughly $300.

For 1993, we have expanded the goal to 2,000 installations with nearly a $5 million budget. The new program incorporates volume bidding of contractor supplied, installed, and warranted systems. SMUD provides marketing support, allowing contractors to focus on installations and service. After the first bidding cycle, SMUD awarded contracts for the furnishment and installation of 195 systems at a cost per system of about $2,500, a savings of over $1,000 from 1992. SMUD further rebates an average of $850, representing SMUD's value of the system's energy and peak demand savings. The $1,650 balance can be financed by SMUD for up to 10 years at 7.6% interest, giving the customer a monthly loan payment of $19.68. Meanwhile, the average, 4-person household should save $27 per month, and the average 3-person household $21. We evaluate bids from contractors on the basis of a system life-cycle cost, estimates of energy and peak demand savings, system reliability, and contractor qualifications. SMUD weights reliability quite heavily.

Twenty-five Residential Energy Specialists have completed SMUD's solar training course which includes solar energy fundamentals, solar hot water system design, operations and installation inspection, and solar siting. The program is made available to customers during in-home energy audits. We expect to perform about 5,000 audits this year. SMUD also uses direct mailers to solicit interest. The first mailing generated nearly 1,000 responses.

Preliminary performance evaluations for 1992 are encouraging. SMUD compared energy savings estimates (obtained with the computer program F-Chart) to the bills of 40 customers who installed four different types of solar water heaters last July. Over the following three and a half months, the average monthly savings in homes with the installations was 310 kWh. This compares with savings estimates (from F-Chart) of 330 kWh per month for the same period. The marginal electricity rate for these customers during the summer averages more than 10cents per kWh, so these customers likely saved more than $30 per month.

SMUD expects the more comprehensive bill analysis project planned for later this year to support these preliminary findings. We plan to evaluate customer satisfaction and overall program delivery effectiveness, and to perform a (weather- and demographic-adjusted) utility bill analysis of all program participants. SMUD also plans to conduct pre-and post-installation metering of 30-60 systems this summer to determine actual peak load reduction levels.

Finally, in a joint effort with National Renewable Energy Laboratory, SMUD will perform short-term instrumented monitoring of approximately 18 installations in each of two different seasons. The objective is to estimate annual savings and further validate existing computer simulation models for the benefit of SRCC. (SMUD has been working with local contractors, manufacturers, and the SRCC to complete and implement OG-300, the national certification and rating for solar hot water systems.) We expect continued improvements in system cost-effectiveness and reliability as we move toward our goal of 32,000 installations by 1998.

  • -- Cliff Murley

Cliff Murley is the manager of SMUD's solar water heater program.


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